New Developments and Application in Chemical Reaction Engineering

Jian-Jiang Zhong , in Studies in Surface Science and Catalysis, 2006

one INTRODUCTION

Biochemical reaction engineering (BRE) plays an important role in the biotechnology world, specially in the industrial application of biotechnology/bioscience enquiry achievements. With the rapid development of biotechnology, at that place is an accelerated trend in interdisciplinary inquiry between BRE and other fields. Under the circumstances, novel BRE concepts/methodologies are adult to handle new processes and new targets, which too contributes to the advancement of biotechnology and other disciplines. In this article, by taking cell cultures for production of valuable secondary metabolites as a typical case, several examples are demonstrated regarding the impact of interdisciplinary study on BRE.

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11th International Symposium on Process Systems Applied science

Robert J. Flassig , Kai Sundmacher , in Computer Aided Chemical Engineering, 2012

Abstract

Biochemical reaction networks in the grade of coupled ordinary differential equations (ODEs) provide a powerful modeling tool to empathise the dynamics of biochemical processes. During the modeling procedure a pool of competing nonlinear models is generated, from which the most plausible set up has to be selected, given distributed model parameters and hence distributed model prediction. At this bespeak, robust (=  taking distributed model responses into account) model-based stimulus experiments can be used, to find experimental weather condition at which models show maximal dissimilarities to focus experimental efforts. Response variabilities are typically obtained from linearization. Here we compare this method to the nonlinear Sigma-Point approach for a nonlinear, multi-stable model and show its reward for model discrimination, particularly for big parameter variances.

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Phosphoryl and Sulfuryl Transfer☆

T.A.S. Brandao , ... S.C.L. Kamerlin , in Reference Module in Chemistry, Molecular Sciences and Chemic Applied science, 2016

Abstract

Biochemical reactions of phosphate and sulfate esters are ubiquitous in the living globe, and are found throughout many pathways involving metabolism, biosynthesis, control of transcription, energy storage, and replication. This chapter describes the mechanisms by which phosphate and sulfate monoesters undergo uncatalyzed and enzyme-catalyzed hydrolysis by phosphatases and sulfatases, respectively. Relative to the slow rates of the uncatalyzed reactions of their substrates, these enzymes produce rate accelerations that are among the greatest of any enzymes yet described. Interestingly, nature has evolved several quite different catalytic strategies to accomplish this. This review summarizes the electric current state of knowledge of several phosphatases and sulfatases. Phosphatases and sulfatases constitute a large group of enzymes, with structural and mechanistic diverseness. Within each group, one finds enzymes that utilize completely different catalytic machinery and mechanisms to accomplish the same reaction. We as well summarize the mechanistic tools that have been used to written report the chemical science and biochemistry of sulfate and phosphate esters, with references to comprehensive treatments of these methods for those who wish more thorough explanations of the tools of enzymology and concrete organic chemistry.

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Protease Inhibitors and Their Applications: An Overview

Kiran R. Marathe , ... Vijay L. Maheshwari , in Studies in Natural Products Chemistry, 2019

Introduction

Biochemical reactions in living systems are catalyzed by a series of enzymes and are tightly controlled by specific protein and nonprotein enzyme inhibitors. Enzyme inhibitors bind to an enzyme and arrest its catalytic action [1], which brand them useful tools in the study of enzyme structures and reaction mechanisms and their applications equally therapeutics in medicine and biocontrol agents in agriculture [2–six]. Proteases play a major role in the posttranslational processing of proteins, poly peptide catabolism, and diverse pathological processes, and therefore, they become a natural target for protease inhibitors (PIs). Several natural, specific, and selective PIs are now known as major regulating proteins to command proteolytic action in all life forms [7]. PIs find diverse applications in diagnostics and therapeutics, to treat various microbial [hepatitis, herpes, AIDS, aspergillosis], mortal (arthritis, muscular dystrophy, malaria, cancer, obesity), neurodegenerative, and cardiovascular diseases [8]. In add-on, they are indispensable tools to use to (ane) written report enzyme structure; (2) control herbivorous pests and fungal, postharvest microbial infections [nine–xi]; (3) stabilize proteases in commercial products [12]; (4) prevent undesired proteolysis during heterologous expression of protein extraction; and (5) prolong the shelf life of many proteinaceous types of seafood [thirteen]. The discovery of PIs in plants displaying specific inhibitory activities against digestive enzymes of insects drew attention to controlling phytophagous insect pests and pathogen (fungal) invasion through antinutritional interactions and losses in crop yield and quality [fourteen]. The proven biocontrol action of PIs confronting plant pathogens and herbivorous pests [eleven] may aid to curtail extensive chemic pesticide use, eventually reduce heavy losses in crop yield, and amend the quality of agricultural produce [fifteen]. At nowadays, there are several small PIs for each mechanistic class of proteases [serine, cysteine, aspartyl, and matrix metalloproteases (MMPs)] identified from plants, animals [sixteen,17], and microbial sources [xviii–20]. The majority of PIs come from plants, and a few have animal origins; they (1) exhibit limited specificity, (two) inhibit merely proteases (trypsin) belonging to a unmarried mechanistic course, (3) bind and block access to the agile site of target proteases and exercise not bind in a strictly substrate-like way, (4) insensitive to the pH range ii–x with varying thermostability [21], (5) show poor structural stability in a multifariousness of environmental weather condition, (6) accumulate at high concentrations in tissue in response to wounds (10% of the full proteins) [22], (7) function as defence force agents to protect plants from invading pests [23], (8) exhibit competitive inhibition, and (9) require more space, fourth dimension, and price to obtain in a pure form because a long duration is required for the cultivation/growth of plants and animals.

The application of PIs from demote to business for agronomics/biotechnology purposes depends on (1) structural stability under a range of environmental conditions, including pH and high affinity for diverse digestive proteases of pests [sixteen,22]; (2) rapid bounden to their target protease(s) to form a tight complex with an clan charge per unit constant (K ass) of >   105 per M and a binding constant K i of <   10−   9  M [24]; (three) broad specificity toward the major mechanistic classes of proteases; (4) the capacity to function even in low concentrations; and (5) economic production. Microorganisms are a low-cost source of PIs due to their rapid growth and mass product past simple-medium engineering science, greater multifariousness in inhospitable environments, acquiescence for genetic modification for overproduction or overexpression in transgenic plants, and resistance to proteolytic cleavage [19,25,26].

Many microbes from a variety of types of ecological habitat, such as terrestrial, marine, and soil, take been reported for a number of low-molecular-weight protein and nonprotein inhibitors [27]. The periplasmic space in Escherichia coli contains ecotin, which inhibits trypsin, elastase, and chymotrypsin [28]. The majority of extracellular protein inhibitors of element of group i proteases have been produced by the genus Streptomyces [29]. The first Streptomyces subtilisin inhibitor (SSI) was reported equally existence derived from Streptomyces albogriseolus; thereafter, diverse Streptomyces species have been reported to produce like SSI-like proteins, which are now classified as existence in the SSI family [29]. In add-on to beingness a potent low molecular weight plasmin inhibitor, plasminostreptin from Streptomyces antifibrinolyticus [30], trypsin inhibitors from Streptomyces lividans and Streptomyces longisporus [31], transglutaminase-activating metalloprotease inhibitors (MPIs) from Streptomyces spp. [32], and kexstatin from Streptomyces platensis [33] accept been isolated. These PIs in microbes probably have evolved as a protective mechanism in all habitats, including inhospitable ones. Microbes represent a preferred source of natural PIs to understand inhibitor-enzyme interactions for applications in agriculture, therapeutics, food manufacture, and other environments. The current fermentative production of PIs using microbes suffers from lower yields, cost-intensive processes, and difficulties in recovery, thereby preventing its wide use for demote-to-business scale-up. Various statistical tools for media optimization can be meaningfully utilized for yield enhancement of PIs from microbial sources. Marathe et al. [five] reported a >   30% increment in yield with a PI by optimizing various culture conditions through Plackett–Burman design (PBD) and the response surface method (RSM) using a central blended blueprint (CCD) by Streptomyces sp. isolated from soda lake Lonar. Alternatively, large-scale production of PIs using recombinant techniques is possible, but target PI accumulates and precipitates in host cells as inclusion bodies, resulting in depression recovery.

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Laboratory Methods in Enzymology: Jail cell, Lipid and Saccharide

Vaishnavi Rajagopal , Jon R. Lorsch , in Methods in Enzymology, 2013

Abstract

Many biochemical reactions that occur inside the cell are thermodynamically unfavorable. Nevertheless, when these reactions are coupled to NTP (nucleoside triphosphate) hydrolysis, the free energy derived from the hydrolysis of the phosphodiester bond helps bulldoze the reaction in the favorable management. Examples of such proteins tin can be found in almost all facets of cellular metabolism: glycolysis and the TCA cycle, protein biosynthesis, Deoxyribonucleic acid and RNA metabolism, cellular trafficking, cell signaling, prison cell partition etc. Thus, characterization of the NTPase activity of these proteins in vitro tin help in understanding the role of the poly peptide in circuitous cellular processes.

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The Phenomena of Interference in Chemical and Biochemical Redox Reactions with Hydrogen Peroxide

Tofik K. Nagiev , in Coherent Synchronized Oxidation Reactions by Hydrogen Peroxide, 2007

6.4 CO-FACTORS AND THEIR ROLE IN THE INTERACTION AND SYNCHRONIZATION OF BIOCHEMICAL REACTIONS

Diverse biochemical reactions interact in all living organisms. Therefore, it is desirable to determine the chemical interference or chemical conjugation in such systems.

Thus, a logical question arises: what is newly introduced by the theory of synchronous chemical reaction interaction to decoding of the machinery and functions of enzymatic systems?

Start of all, the interference pattern of the biochemical interaction between reactions volition shed light on their synergic mechanism and the associated outcome on the control functions of enzymatic systems, especially those immobilized on membranes: the overwhelming majority of the enzymes' work on the surface of prison cell and sub-cell membranes. Moreover, interference presentation allows the detection of the origin of agile intermediate substances, which form and operate the communication channels between ii or more biochemical reactions, defines the co-factor role and gives an opportunity to induce thermodynamically hindered biochemical reactions.

Co-factors, as a rule, are the integral part of enzymes, without which the cell metabolism is impossible.

Co-factors are metal ions or non-protein organic compounds; still, many enzymes require the presence of both co-factors.

Co-factors are added to the catalytically inactive poly peptide function of enzymes, the and so-called apoenzyme. In cases where this bond in a complex is strong plenty, information technology is called the prosthetic group.

In the framework of the currently developing concept of chemical interference, of primary interest are co-factors transferring chemical groups, hydrogen atoms or electrons.

The key role of co-factors concludes in the formation of the active catalytic site of the enzyme, with the help of which substrate is stock-still and its conversion is simplified and intensified.

It should be noted that derivatives from vitamins possessing relatively more than complex structures are besides co-factors. Unfortunately, they cannot exist synthesized in animate being organisms.

Naturally, organisms are supplied with vitamins in food, and vitamin deficiency can crusade specific diseases.

Equally mentioned above, redox enzymes (oxidoreductases) are divided into iv large groups: dehydrogenases, oxygenases, oxidases, and peroxidases and catalases.

Dehydrogenases responsible for hydrogen transfer between substrates possess NAD+ (nicotinamide) as the coenzyme, owing to which chiral alcohols are formed from ketones and aldehydes.

Participating in dehydrogenase reactions, the NAD+ coenzyme is reduced to NADN by the following biochemical reaction:

(6.22)

This reaction is stereospecific and synthesizes 1 of ii possible isomers in α- or ß-position.

To clarify reaction (six.22) in the framework of the chemical interference concept, it should exist divided into two component processes: the primary and the secondary overall reactions.

In this example, the primary reaction is presented by the so-called citric acid cycle with the participation of various NAD+-dependent dehydrogenases synthesizing corresponding last products typical of this bicycle. However, agile intermediate NAD+H− and H+ particles formed in the course of these reactions are able to induce reduction of aldehydes and ketones to corresponding chiral alcohols with the simultaneous regeneration of the NAD+ co-gene.

Thus, the secondary overall reaction will represent a circuitous biochemical reaction consisting of elementary stages in which NADH and H+ are formed and consumed for reduction of aldehydes and ketones.

Using experimental data, the interference pattern demonstrates kinetic curves of the chief and secondary reactions. Hence, information technology reflects the machinery of possible command influences on the system, for example, past means of concentration of one initial substrate or another and terminal products of both reactions.

The to a higher place indicates the importance of specific requirements to the synthesis of enzyme biosimulators.

The problem of biomimetic model design simulating the activity mechanism of corresponding enzymes is based on the idea of structural-functional conformity. In 1971, alcohol dehydrogenase was primarily synthesized [123]. In this biomimetic organization the product is formed due to direct electron transfer from the reduced co-factor (NADH) analog to aldehyde. Notation that the display of alcohol dehydrogenase catalytic activeness requires the presence of zinc (II) ion.

Simulation of the contrary dehydrogenase reaction induced the use of crown ethers equally NADH models [124]. It is shown that hydride-ion transfer past crown ethers happens 3000 times faster than in the case of different carriers. It is believed that crown ether provides for the required cation complex formation level, which displays some typical features of imitation enzymes. In particular, on the one hand, crown-ether biosimulator is an acceptor site for substrate fixing; on the other mitt, it is a catalytic site for stock-still substrate conversion. Thus, similar biosimulators are of dual interest: as simulation enzyme models and effective chemic agents [125].

Of course, the creation of co-gene models requires a comprehensive cognition of structural and catalytic backdrop of corresponding enzymes. For example, postulated hydride ion may exist opposed by a simpler reduction mechanism involving two-electron transfer. In this connectedness, Hamilton believes that if hydride ion is really directly transferred in dehydrogenase reactions, this mere process is unique not just in biology, because H+ + 2e − transfer is more favorable [126]. Withal, the author failed to distinguish these 2 possibilities. Broadly speaking, information technology is very hard to judge this unambiguously.

When simulating the booze dehydrogenase, the investigators met with economic problems because the NAD+ co-factor is very expensive. Therefore, several methods of its regeneration were developed, among which the most constructive method is not-enzymatic continuous regeneration of catalytic amounts of NADHL and NAD+ with sodium dithionite [127]. This method tin can be used for HLADH synthesis, used in the catalytic reduction of a wide pick of aldehydes and ketones.

Even so, the reverse reaction of alcohol oxidation in this organization can be performed with flavin co-gene added (FMNH2 → FMN), where molecular oxygen is reduced to HtwoOtwo. The entire biomimetic process nether consideration is well illustrated by the following diagram [128]:

(6.23)

The absolute reward of the biomimetic systems suggested above is that they possess a gear up of properties that cannot be reproduced in i stage by traditional methods of chemical catalysis. Like to corresponding enzymes, these properties help the systems mentioned to effectively catechumen the substrate.

Permit the states now apply these ideas almost the features of co-cistron machinery of enzymatic reactions and their analogs to the analysis or interpretation of substrate conversion in terms of synchronous reaction interaction (chemical interference). Every bit usual, we commencement need to place the primary reaction which synthesizes NADH, the highly active intermediate compound, to the system. A primary reaction shaped every bit follows can be just deduced from the diagram (half dozen.23):

where RCHiiOH and

are the substrate and the product, respectively.

The secondary reaction is carried out with the direct involvement of the intermediate generated to the system co-ordinate to the following process:

In the primary reaction two electrons are transferred in one phase from the substrate by NAD+ in the form of hydride ion (H−); the 2d hydrogen atom is detached from the substrate molecule as proton (hydrogen ion H+). Note that NAD-dependent dehydrogenases participate in the citric acid cycle, saccharide exchange, etc. in mitochondria.

Generalizing the in a higher place, it can be shown that cellular dehydrogenases transfer hydrogen atoms from diverse substrates by NAD+, in NADH form, which is the unique (full general) intermediate, among those generated by diverse NAD+-dependent dehydrogenases to the arrangement. This statement does not exclude H from the reaction book, where it is too formed in dehydrogenase reactions.

At the next phase, two electrons fixed by hydride ion (H−) in NADH coenzyme are transferred to flavin adenine dinucleotide (FAD) dependent dehydrogenase, located on the internal mitochondrial membrane. In this reaction the strongly spring prosthetic group of FAD-dehydrogenase is reduced. The office of the FAD-dehydrogenase prosthetic group is played by FAD; hence, two electrons (by illustration with hydride ion) are transferred from NADH to FAD past the reaction:

NADH + FAD + H + ↔ NAD + + FADH 2

In the Hamilton mechanism, widely practical by biochemists, 1 proton and two electrons are or hydride ion is transferred. It is justified by the fact that proton has no electron encompass and, therefore, is quite movable and more highly effective in biological media [126].

This question will be more or less cleared up only later model reaction investigations. The majority of oxidases are FAD dependent and able to transfer oxygen to the substrate molecule. NAD+ coenzyme does not possess this property. For example, flavin-dependent monooxygenases activate molecular oxygen and then that i cantlet of oxygen can exist added to the substrate molecule hydroxylating or epoxidizing it, whereas the 2nd cantlet of oxygen is reduced to H2O.

The cyclic mechanism of monooxygenase reactions performed in flavin-dependent systems is shown in the diagram beneath [128]:

where

By analogy with carbenes, this mechanism is known by the proper name 'oxene mechanism'. The diagram shows that the oxygen molecule reacts with the reduced flavin is activated and only then oxidizes the substrate in accordance with the ion mechanism; hence, free electron spins in O2 are necessarily preserved. Thus, it is suggested that reduced flavin forms fixed H2O2 via interaction with O2. In this class, H2O2 is regrouped to flavin-4a-hydroperoxide (HO2) and, therefore, obtains higher reactivity. In its turn, affected by H+, flavin hydroperoxide is regrouped to carbonyl oxide, which is a hydroxylating and an epoxidizing agent. To prove the reality of such a system, the mechanism developed for ozone reaction with unsaturated compounds is shown:

The main disadvantage of Hamilton's machinery [126] is the existence of an open flavin ring shape. Moreover, Hamilton's mechanism is based on the idea that there is no direct oxygen transfer to the substrate, which is conspicuously illustrated by the post-obit expression:

The mechanism suggested in Ref. [129] does not imply the formation of an intermediate product with an open up ring. Active oxaziridine-4a,5-flavin benzoxide formed from flavin hydroperoxide is assumed to be the intermediate. This machinery based on the electrophilic type of the oxaziridine system is justified in multiple examples, united in the following diagram [128]:

In the framework of these ideas, the phenol hydroxylation mechanism is implemented by oxygen transfer from the oxaziridine intermediate to phenol giving dissimilar intermediate compounds—benzene epoxide:

This suggestion is already known. Indeed in 1969, it was stated [130] that monooxygenase oxidation of some effluvious compounds produced intermediates, shaped as epoxides of these aromatics:

Some other idea, theoretically justified by Goddare [131], about the hydroxylation mechanism of phenol compounds is based on the proposition that the active intermediate chemical compound is presented past biradical particles.

As shown by this method, besides biradical, another intermediate compound is formed. It represents a complex of flavin bound to phenol by two atoms of oxygen:

This is the multistage method. It suggests the formation of several active intermediate substances, including biradical particles, which in the author's opinion has less probability for enzymatic transformation of the substrate.

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OVERVIEW OF EXPERIMENTAL FINDINGS

V. Nabokov,Ada or Ardor: A Family Chronicle, in Magnetobiology, 2002

two.ane.one Objects studied

Among the commonest objects studied are:

•

biochemical reactions ( Jafary-Asl et al., 1983; Litovitz et al., 1991; Shuvalova et al., 1991; Markov et al., 1992; Novikov, 1994; Markov et al., 1998; Blank and Soo, 1998; Ramundo-Orlando et al., 2000), thirteen

•

Deoxyribonucleic acid impairment and repair processes (Whitson et al., 1986; Nordensen et al., 1994),

•

Deoxyribonucleic acid−RNA synthesis (Liboff et al., 1984; Takahashi et al., 1986; Goodman and Henderson, 1991; Phillips et al., 1992; Goodman et al., 1993a; Lin and Goodman, 1995; Bare and Goodman, 1997),

•

enzymes — membrane ion pumps (Blank and Soo, 1996),

•

cells (Spadinger et al., 1995; Alipov and Belyaev, 1996; Sisken et al., 1996):

*

amoeba cells (Berk et al., 1997),

*

bacterial cells (Moore, 1979; Alexander, 1996),

*

E. coli (Aarholt et al., 1982; Dutta et al., 1994; Alipov et al., 1994; Nazar et al., 1996),

*

yeast cells (Jafary-Asl et al., 1983),

*

Candida (Moore, 1979),

*

cells of plants (Fomicheva et al., 1992a; Belyavskaya et al., 1992),

*

fungi (Broers et al., 1992),

*

algae (Smith et al., 1987; Reese et al., 1991) and

*

insects (Goodman and Henderson, 1991).

*

animal cells (Takahashi et al., 1986):

º

fibroplasts (Whitson et al., 1986; Ross, 1990; Matronchik et al., 1996b; Katsir et al., 1998),

º

mouse epidermis (Due west et al., 1996),

º

erythrocytes (Serpersu and Tsong, 1983; Mooney et al., 1986; Shiga et al., 1996),

º

lymphocytes (Conti et al., 1985; Rozek et al., 1987; Lyle et al., 1988; Goodman and Henderson, 1991; Lyle et al., 1991; Walleczek, 1992; Yost and Liburdy, 1992; Coulton and Barker, 1993; Lindstrom et al., 1995; Tofani et al., 1995),

º

leucocytes(Barnothy, 1956; Goodman et al., 1989; Picazo et al., 1994; Sontag, 2000),

º

osteoblasts (Luben et al., 1982),

º

neoblasts (Lednev et al., 1996),

º

endothelia (Yen-Patton et al., 1988),

º

of salivary glands (Goodman et al., 1983; Goodman and Henderson, 1988),

º

thymocytes (Walleczek and Budinger, 1992; Matronchik et al., 1996b),

º

amniotic (Simko et al., 1998),

º

bone cells (Fitzsimmons et al., 1989).

*

tumor cells (Phillips et al., 1986b; Wilson et al., 1990; Lyle et al., 1991):

º

Ehrlich carcinoma (Garcia-Sancho et al., 1994; Muzalevskaya and Uritskii, 1997),

º

breast cancer MCF-7 (Harland and Liburdy, 1997; Blackman et al., 2001),

º

pheochromocytoma (Blackman et al., 1993),

º

leukemia in humans U937 (Smith et al., 1991; Garcia-Sancho et al., 1994; Eremenko et al., 1997),

º

E6.ane (Galvanovskis et al., 1999),

º

carcinoma of mouse embryo F9 (Akimine et al., 1985),

º

glioma N6 (Ruhenstroth-Bauer et al., 1994),

º

human being osteosarcoma TE-85 (Fitzsimmons et al., 1995).

*

tissues of the brain (Bawin and Adey, 1976; Blackman et al., 1979; Dutta et al., 1984; Blackman et al., 1988, 1990; Martynyuk, 1992; Agadzhanyan and Vlasova, 1992; Espinar et al., 1997; Lai and Carino, 1999),

*

nerve (Semm and Beason, 1990),

*

intestine (Liboff and Parkinson, 1991),

*

os (Liboff and Parkinson, 1991).

•

organs:

*

encephalon (Kholodov, 1982; Richards et al., 1996),

*

middle (Kuznetsov et al., 1990).

•

physiological systems:

*

central nervous (Bawin et al., 1975; Kholodov, 1982; Lerchl et al., 1990),

*

neuroendocrine (Reiter, 1992),

*

allowed (Lyle et al., 1988).

•

organisms:

*

plants (Pittman and Ormrod, 1970; Kato, 1988; Kato et al., 1989; Govorun et al., 1992; Sapogov, 1992; Smith et al., 1995),

*

plant seeds (Ružič and Jerman, 1998; Ružič et al., 1998),

*

kidneys (Ružič et al., 1992),

*

insects (Ho et al., 1992),

*

rats (Wilson et al., 1981; Ossenkopp and Ossenkopp, 1983; Thomas et al., 1986; Sidyakin, 1992; Temuriyants et al., 1992a; Pestryaev, 1994; Kato et al., 1994; Kato and Shigemitsu, 1996; Deryugina et al., 1996; Nikollskaya et al., 1996) and

*

embryos of rats (Delgado et al., 1982; McGivern et al., 1990),

*

mice (Barnothy, 1956; Kavaliers and Ossenkopp, 1985, 1986; Picazo et al., 1994),

*

newts (Asashima et al., 1991),

*

worms (Jenrow et al., 1995; Lednev et al., 1996a,b),

*

pigeons (Sidyakin, 1992),

*

chickens (Saali et al., 1986),

*

snails (Prato et al., 1993, 1995),

*

human organism (Akerstedt et al., 1997; Sastre et al., 1998).

•

ecosystems and bio-geocenosis (Uffen, 1963; Opdyke et al., 1966; Hays, 1971; Valet and Meynadier, 1993; Feychting et al., 1995; Belyaev et al., 1997),

•

solutions of amino acids — although they are no biological objects, they display MF effects that are very close in essence to those discussed — (Novikov and Zhadin, 1994; Novikov, 1994, 1996).

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Chemical and Synthetic Biology Approaches To Understand Cellular Functions - Part C

Alexandra V. Chatzikonstantinou , ... Andreas G. Tzakos , in Methods in Enzymology, 2020

1 Introduction

The biochemical reactions in a cell are constantly tuned, intertwined and calibrated in a coordinated fashion so equally to build up and interruption down cellular components and ultimately fulfill all cellular functions. To achieve this fragile equilibrium cells systematize the reactions in enzyme-powered paths. Single enzymatic steps can be linked up and shape numerous metabolic circuits. However, enzymes do not employ a single substrate but an assortment of dissimilar compounds leading to chemical diverseness. This catalytic promiscuity has frequently remained elusive and uncharted in the absence of efficient tools to decompose this information. Charting the substrate diversity of an enzyme is of immense importance. For instance, the different metabolites in case of drugs that can emerge from specific enzymes should be identified since they can be harmful for the human health. The recognized enzyme promiscuity has also been utilized to synthesize different compounds with "green" processes. Numerous inquiry groups utilized this enzyme promiscuity to generate bioactive compounds via biocatalysis ( Choi, Han, & Kim, 2015; Patel, 2018; Lord's day, Zhang, Ang, & Zhao, 2018). Another currently active trend in drug discovery is the evolution of drug precursors (prodrugs) that can exist activated to yield the active component in a specific cell microenvironment. For example, in oncology, researchers exploit enzymes that are selectively overexpressed in cancer cells (Giang, Boland, & Poon, 2014; Mahato, Tai, & Cheng, 2011) to build upwardly cancer responsive prodrugs. Thus, in a drug discovery pipeline it is very important to develop tools to rapidly validate such enzyme responsive prodrugs in a simulated cellular environs. Furthermore, there is a quest to notice cellular responsive chemosensors then as to chart cellular functions, like, for example, the pH microenvironment in cells (Cardone, Casavola, & Reshkin, 2005), the intracellular redox potential (Hegedűs et al., 2018), and the cell metabolic activity (3-(four,five-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, MTT assay) (Van Meerloo, Kaspers, & Cloos, 2011). Along these lines there is a articulate need to establish tools and processes to foster the use of enzymes as systems to generate new compounds, also every bit to monitor the products or metabolites. Such tools could enable the charting of enzyme promiscuity, discovery of substrates of uncharacterized enzymes, help in the development of prodrugs activatable by intracellular enzymes and synthesize bioactive therapeutic, diagnostic or theranostic compounds. Although biotransformation tin can be implicated in all these processes, several challenges be to exploit them in full, since the products can be chemically circuitous and could too constitute complex mixtures; thus the isolation and characterization could exist challenging.

In this chapter, we describe how to ready the "NMR tube bioreactor" (Chatzikonstantinou et al., 2018). This is a three step process that is completely carried out within an NMR tube (Fig. 1). The NMR tube bioreactor could let for predicting potential enzyme substrates and the regioselectivity of the enzymatic reaction, for charting the formed prodrugs in real fourth dimension and for evaluating the resulting products as interactors of proteins of interest.

Fig. 1

Fig. 1. The neat advantages of the apply of the NMR tube bioreactor: (i) use of low volumes of aqueous solvent, (ii) elimination of all purification steps of a classical constructed procedure, (3) apply of mild reaction conditions without protection/de-protection steps, and (iv) immobilization of the enzyme allowing for the recycle of the catalysts for several reactions. The simultaneous screening of several compounds allows a reduction of the experiments that should exist performed.

Equally illustrated in Fig. 1, in the first stride, one tin can apace predict in an NMR tube: (ane) the capacity of a compound or a mixture of compounds to serve as enzyme substrate(s) and (2) the potential regioselectivity of the biotransformations. So, in the second step i tin can monitor in real time the germination of enzymatically generated products likewise equally optimize the enzymatic reaction yield by quickly screening different conditions. Of importance, a real time monitoring of the reaction product(southward) is conducted in this step without any prior fractionation or purification. In the third step, the biotransformed products are evaluated as ligands in a protein-ligand screening process.

In this chapter, we will illustrate in detail the required steps for the successful application of the NMR tube bioreactor. To illustrate the awarding of the first ii steps, nosotros selected, as putative enzymatic substrates, flavonoids due to their inherent scaffold complexity. As a template enzyme, we utilise lipase B from Pseudozyma (Candida) antarctica (CaLB) for either ester synthesis or alcoholysis. Furthermore, to evaluate the applicability of the process, we use the enzyme cytochrome c iso-one C107T (Cyt-c) for the oxidation of a substrate. For the third step, that is ligand-protein interaction screening on the enzymatically derived products, we illustrate two examples using the prototypical protein carrier BSA and the intrinsically disordered protein α-synuclein. The ii main approaches, ligand-based screening and protein-based screening, will exist discussed. Through the analyzed protocols the user will exist able to sympathise how to incorporate the process in a drug discovery pipeline too as in drug metabolite screening.

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Isotope Labeling of Biomolecules - Labeling Methods

Lukasz Skora , ... Alvar D. Gossert , in Methods in Enzymology, 2015

4.4.2 Relevant Metabolism for 2H Labeling

The relevant biochemical reactions involved in reducing deuteration levels are in part the ones already discussed for xvN and 13C labeling. The scheme of primal amino acid metabolism in Fig. 12 summarizes these reactions. Since glucose cannot exist added in deuterated class to insect cell media, Glx, Asx, and Ala will be synthesized with protonated carbon chains at like levels as adamant for the example of xiiiC labeling. Also hither, Ala synthesis can exist controlled with the inhibitor l-cycloserine. However, in improver to these initial reactions, the blastoff positions of the amino acids involved in transaminase reactions volition be protonated. Pro, Arg, Gly, Ser, Thr, and Met practice not seem to be synthesized at relevant levels from glucose. However, Gly is heavily protonated at the alpha position in an of import housekeeping reaction, which produces North5,Nx-methylene tetrahydrofolate that is used in numerous methylation reactions (Fig. thirteen; Kofuku et al., 2014). All these reactions contribute to lower and less compatible incorporation of deuterium than 13C or 15Due north. Additionally, deuterated media reduce protein yields to thirty–60% of what is obtained in nonlabeled media. In contrast, for 13C and xvNorth labeling, similar poly peptide amounts are obtained as in nonlabeled media. Reduced yields are probably also due to reactions like 3, 5, and four (reversed) in Fig. 12. These lead to deuterated carbohydrates, which are introduced into the citric acid cycle. These deuterated intermediates dull down reactions involving the breakage of covalent hydrogen bonds sevenfold, therefore acting as weak inhibitors of the citric acid bike. This probably leads to decreased performance of the cells, which ultimately results in lowered protein amounts. Inhibiting enzymes 3–5 (Fig. 12) could potentially result in increased protein yields and at the same fourth dimension, college and more uniform isotope incorporation. Initial experiments with the inhibitors l-cycloserine (inhibits enzyme v in Fig. 12; Wong et al., 1973), aminooxyacetic acid (three) (Morita et al., 2004; Rej, 1977), and bithionol (iv) (Li, Smith, Walker, & Smith, 2009), however, showed no improved effect over using l-cycloserine solitary (Sitarska et al., 2015).

Effigy 12. Overview of most relevant metabolic pathways for labeling in insect cells. The bottom plane (blackness) depicts glycolysis and the citric acid cycle; selected metabolites are indicated with their names. The middle level (blueish, gray in the print version) shows amino acids that are synthesized in a i-step reaction from the respective carbohydrates by improver of ane nitrogen. The top level (light blueish, calorie-free gray in the print version) shows amino acids with withal an additional nitrogen. Enzymatic reactions are marked with arrows and the enzymes are enumerated equally follows: ane: asparagine synthetase (Fig. half dozenB), 2: glutamine synthetase (Fig. sixA), 3: aspartate transaminase (Fig. 9, centre), 4: glutamate dehydrogenase (Fig. 9, left), 5: alanine transaminase (Fig. 9, right).

Figure xiii. Alpha-protonation of glycine. The reaction producing N5,Northward10-methylene tetrahydrofolate, an important vitamin for methyl transfer reactions, leads to protonation of Gly at the alpha position.

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Reckoner Methods, Role C

Don Kulasiri , in Methods in Enzymology, 2011

1 Introduction

Molecular fluctuations in biochemical reaction systems are important within many fields, but nosotros focus on the subsystems associated with gene expresion in this chapter. Variations in phenotypic characteristics have been observed in the genetically identical cells of organisms ranging in complexity from bacteria to mammals, and are hypothesized to exist an important factor in evolution as well as in the physiological evolution ( Kirschner and Gehart, 2005). Only in recent years, new experimental techniques in molecular biology, such as fluorescent reporters, allow stochastic cistron expression to be quantified in vivo (east.g., see Austin et al., 2006; Blake et al., 2003; Elowitz et al., 2002; Kaern et al., 2005; Ozbudak et al., 2002; Pedraza and van Oudenaarden, 2005; Raser and O'Shea, 2004). These elegant experiments, along with the associated mathematical studies, have profoundly facilitated our understanding of the sources and consequences of such stochasticity in genetic regulatory networks. Such stochasticity are divided into intrinsic dissonance and extrinsic dissonance; the former is associated with the gene and is dependent on the gene, whereas extrinsic racket is due to the surrounding biochemical reactions and diffusion processes within the cell, and therefore, is contained of the gene. While information technology is of import to understand the "noise" associated with the above-mentioned molecular processes in terms of extrinsic and intrinsic components, nosotros consider these noises to exist the molecular fluctuations having mechanistic and thermodynamic characteristics. Some of these processes are thermodynamically irreversible (east.g., mRNAs are translated into proteins, merely we have not seen proteins becoming mRNAs), and the fluctuations are intimately connected to the well-established theory of fluctuations and dissipation (Keizer, 1987).

Mathematical models and the associated methods are essential parts of gene expression enquiry, and some of the studies discussed above incorporate probabilistic mathematical models based on masters equations approach (Kampen, 2001), the formulation of which is based on the transition probabilities of molecules from one form to another course. Some other studies have purely a numerical simulation approach based on the almost pop Gillespie's algorithm (Gillespie, 1977) for reaction kinetics or many variants of information technology because it works well when the molecule numbers are low, and is based on audio gas-kinetics laws. The Gillespie'due south algorithms are valid for the biochemical reaction systems far away from the thermodynamic equilibrium as well as virtually the equilibrium.

We have chosen molecular reaction subsystems associated with the cyclic rhythms of Drosophila to compute molecular fluctuations associated with gene expression. The biochemical dynamics of the motifs of these subsystems can be represented past chemical reactions which can be used in other applications. We hope that the elucidations within such a data-rich mechanism would enliven the applications of theories. Our discussion here is based on a deterministic mathematical model (Xie and Kulasiri, 2007) developed to represent the transcriptional regulatory networks essential for circadian rhythmicity in Drosophila. The model incorporates the transcriptional feedback loops revealed so far in the networks of the circadian clock (PER/TIM and VRI/PDP1 loops where PER, TIM, VRI, and PDP1 are central proteins in the system). The model simulates sustained cyclic oscillations in mRNA and protein concentrations in constant darkness in understanding with experimental observations. The model is robust given a wide range of parameter variations. The model simulates entrainment by light–nighttime cycles and phase response curves resembling the experimental results. The simulated per 01 , tim 01 , and clk Jrk and E-box mutations are similar to those observed in the experiments (Xie and Kulasiri, 2007). (E-boxes are CACGTG enhancers in the promoter regions of genes, and transcriptional factors (TF) demark to them to activate or repress the transcription of a gene.) One of the master differences in this model is that conventional Hill functions are not assumed to draw the regulation of genes; instead, the explicit reactions of binding and unbinding processes of transcription factors to E-boxes in the promoters were modeled. As the activity around whatsoever promoter region strongly influences the entire gene network, it is oftentimes important to investigate possible molecular fluctuations around this region. By modeling the bindings and unbindings of the TFs to E-boxes as elementary reactions would allow us to investigate the molecular fluctuations associated with Due east-box-mediated gene expression. The purpose of this chapter is to explore the molecular fluctuations in these promoter motifs in general mathematical settings using a near-equilibrium theory of molecular fluctuations based on irreversible thermodynamics and compare the results with those from the well-established Gillespie algorithm. We brand apply of the theory of stochastic differential equations (SDEs) to extend the near-equilibrium theoretical solutions, and the comparisons with the results from the Gillespie's algorithms would point whether we could use the near-equilibrium theory equally an approximation for these reactions, which are usually considered as happening far abroad from the equilibrium. The advantage of a positive comparison, that is, the time evolutions of means and variances are similar in both cases, would permit us to utilize the theory as an approximation for the investigations in molecular fluctuations in the network, which would reduce the computational price significantly.

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