Mechanisms Of Reaction Of Some Flavoprotein Enzymes With Oxygen

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from a series of redox reactions, with oxygen being the final electron acceptor (c) Electron carriers (d) ATP production from a proton gradient across the plasma membrane 8. The end products of photosynthesis in cyanobacteria and plant cells are: (a) Water and oxygen (b) Glucose and water (c) Glucose and oxygen (d) Water and carbon dioxide

Molecular Biosciences, University of Kansas, 1200 Sunnyside

flavoprotein monooxygenases Jose Olucha and Audrey L. Lamb* Molecular Biosciences, University of Kansas, 1200 Sunnyside Ave, Lawrence, Kansas Abstract The N-hydroxylating flavoprotein monooxygenases are siderophore biosynthetic enzymes that catalyze the hydroxylation of the sidechain amino-group of ornithine or lysine or the primary

Reaction of Reduced Flavins and Flavoproteins with

flavoprotein enzymes functioning by radical mechanisms, par-ticularly because other flavoproteins, such as D- and L-amino acid oxidases, glucose oxidase, and glutathione reductase, which do not involve radicals in their reaction, are not inhibited (8). Previous work has demonstrated that the enzyme flavin


The half-lives of the major reactive oxygen species are vastly different, underscoring the necessity for different types ofdefense mechanisms (see Sies, 1993). Highest rate constants for the reaction with target molecules are found for the hydroxyl radical; its reactions are diffusion limited, i.e. they take place practically at the site

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Oxygen is needed to keep aconticase reduced. Oxygen is needed to keep aconitase oxidized. Oxygen is needed to absorb electrons from the reduced cofactors the citric acid cycle produces. Oxygen is needed to produce the needed water for the fumarase reaction. Oxygen is needed to oxidize the NAD+ and FAD cofactors back to NADH and


Oxygen and Reactive Oxygen Species (ROS) Oxygen, or molecular oxygen, is vital for survival of all aerobic organisms. During aerobic metabolism, in normal cells, 30 32 molecules of adenosine triphosphate (ATP) are generated from one molecule of oxygen. During this process, oxygen is reduced into water (4 electron reduction).

An Overview of Antioxidant and free Radicals- A Review Article

13]. Other significant intracellular sources of ROS include microsomal cytochrome P450 enzymes, flavoprotein oxidases and peroxisomal enzymes involved in fatty acid metabolism (Figure 2) Abstract The term antioxidant refers to any molecule capable of deactivating free radicals or reactive oxygen species. Free

Enzymatic Reaction Mechanisms

11.A Nicotinamide-Requiring Enzymes That Do Not Show Direct Hydrogen Transfer 358 11.B Flavin Coenzymes 362-11.C Flavpprotein Dehydrogenases 378 11.D Flavoprotein Oxidases 388 Chapter 12 Flavin- and Pterin-Dependent Monooxygenases 406 12.A Reductive Oxygen Metabolism 406 12.B Flavoenzyme Oxidases/Decarboxylases 408 12.C Flavoprotein

Recent discoveries in the pathways to cobalamin (coenzyme B12

2for BluB, and the reaction requires molecular oxygen. At least three mechanisms for BluB, all involving a hydroperoxide inter-mediate (Fig. 3), have been proposed [13,14]. RECENT EXPERIMENTAL EVIDENCE FOR THE ACTIVITIES OF THE S.TYPHIMURIUM CbiPROTEINS OF THE ANAEROBIC PATHWAY TO COBALAMIN

The taming of oxygen: biocatalytic oxyfunctionalisations

oxygen transfer agent (oxidative half reaction). The resulting C4a-hydroxyflavin eliminates water and thereby returns to the oxidized resting form (Scheme 3). O nlyveryrecentlyanalternative mechanism for oxygenation by a flavoprotein has been revealed. 41 It was shown that the bacterial enzyme EncM, involved in

1 The reaction mechanisms of Groups A and B fl avoprotein

1 The reaction mechanisms of Groups A and B fl avoprotein monooxygenases David P. Ballou and Barrie Entsch Abstract Flavoprotein monooxygenases, found in species ranging from microorganisms to mam-

Chapter 1 Introduction

ring closure or opening. The enzymes that catalyze these reactions are called amidohydrolases, and they are part of a superfamily comprising a diverse set of enzymes that catalyze mainly hydrolysis reactions, and some isomerization reactions. They function on a variety of substrates such as sugars, nucleic acids, amino acids, and

From Structure and Functions of Steroidogenic Enzymes to New

center enzymes and systems responsible for coordina- tion of electron transfer, interaction with substrates, and activation of molecular oxygen; (iii) structural function-

Drug Metabolism

serves to reduce molecular oxygen and form an activated oxygen -cytochrome P-450-substrate complex. 4.This complex in turn transfers activated oxygen to the drug substrate to form the oxidized product. The potent oxidizing properties of this activated oxygen permit oxidation of a large number of substrates.

Same Substrate, Many Reactions: Oxygen Activation in Flavoenzymes

enzymes that can oxidize aromatic compounds with con-comitant reduction of dioxygen into water, whereas mono-nuclear iron dioxygenases and heme-containing P450 mono-oxygenases are effective in many oxygenation reactions.5,6 There is also a large group of oxygen-utilizing enzymes that are devoided of metals and rely on a flavin cofactor

A Review of Electron Transport Mechanisms in Parasitic Protozoa

enzymes containing sulfhydryl groups when p-mercuribenzoate is effective. Some inhibitors like malonate often do not penetrate whole organisms, and some like cyanide and azide are volatile. Nevertheless, the use of inhibitors has been very helpful in enzyme studies. Table I lists a few of the common inhibitors and their sites of action. PLASMODIA

7.03 Flavin-Dependent Enzymes -

(Scheme 1), usually after the product of the reductive half-reaction dissociates, so flavoenzymes frequently have ping-pong kinetic mechanisms. Even when the first product remains bound during the oxidative Scheme 1 Typical catalytic cycle of flavoproteins. 40 Flavin-Dependent Enzymes

The Oxygen Dilemma:ASevere Challenge for the Application of

undesired uncoupling reaction. With this contribution we hope to generate ageneral awareness of the oxygen dilemma and to discuss itsnature and somepromising solutions. Scheme1.The synthetic scope of monooxygenases. Within the enzymes active sites,highly reactive oxygen-transfer species are generated through reductive activationofmolecular

Water Uptake and Extrusion by Mitochondria in Relation to

flavoprotein, between cytochrome b and c, and between cytochrome c and oxygen (cf 26, 105, I I, 205). While the chemical and enzymatic mechanisms of electron transfer and of the coupled phosphorylations are still largely unknown, the re- action pattern shown in Fig. I, which is that proposed by Lehninger et al.

Histochemical activity

and an oxygen deficit is produced in the affected area. Asthe skin lesions are resorbed, a fall in the rate oftissue respiration is observed. In a biochemical study of oxidizing enzymes in leprosy, Naylor(1958)discoveredthatthe amount of dehydrogenasesin aleproma was noticeably greater before treatment than during the course of treatment.

Reactive Oxygen Species - AHA/ASA Journals

2 is degraded to water and oxygen. Aside from SOD or catalase, glutathione peroxidase (GPx) also exerts antioxidant enzymatic function, because it cata-lyzes a reaction that degrades H 2 O 2 by oxidizing reduced glutathione (GSH) to its disulfide form (GSSG). Therefore, SOD, catalase, and GPx represent important antioxidant enzymes within

The Oxygenase Peroxidase Theory of Bach and Chodat and Its

forms of the flavin occur in its catalytic cy cle, the reaction of the reduced form with oxygen generating free peroxide directly [22]. Free reduced flavins do form peroxide intermediates when they react with molecular oxygen [23]. And anoth-er class of flavoproteins, the monooxygenases, in their reduced states do react with oxygen to give a

Minireview Vol. 269, No. 36, Issue of THE 9, 22459-22462

group, the oxidases, reacts rapidly and yields oxidized flavoprotein and H,O, as the only observed products. The fourth group, the monooxygenases, induces a splitting of the 0-0 bond, inserting one oxygen atom into a substrate and reducing the other atom to H,O. All enzymes of the monooxygenase class form readily detectable

The Antimicrobial Activity of Marinocine, Synthesized by

effect of marinocine on oxygen consumption. Cells were washed with phosphate buffer (0.05 M, pH 7) and resuspended to an optical density at 600 nm of 0.4. After stabilization of endogenous oxygen consumption, the compounds to be tested (glucose or marinocine) were injected into the chamber. N-terminal amino acid sequencing.

Flavins on the move - WUR

Flavoprotein monooxygenases perform chemo-, regio- and/or enantioselective oxygenations of organic substrates under mild reaction conditions [1]. These properties along with effective preparation methods turn flavoprotein monooxygenases in focus of industrial biocatalysis. Here we describe two biocatalytically relevant subclasses

Emergence of oxygen‐ and pyridoxal phosphate‐dependent reactions

enzymes employ molecular oxygen as a cosubstrate. Here, we review the biological roles and possible mechanisms of these enzymes, and we observe that these enzymes are found in multiple protein families, suggesting that reaction with oxygen might have emerged de novo in several protein fami-

complex of reduced

reactions catalyzed by simple flavoproteins is now known (1). Some of these enzymes prepared from bacteria are stable and relatively simple to purify, and offer interesting possibilities for detailed study of hydroxylation mechanisms. With two such enzymes, p-hydroxybenzoate hydroxylase from

Crystal Structure of 3-Hydroxybenzoate Hydroxylase from

single-component flavoprotein aromatic hydroxy-lases. The catalytic mechanisms have been investi-gated thoroughly by many structural and kinetic studies. The enzymes share a common catalytic mechanism consisting of two reaction steps; (i) the reduction of enzyme-bound FAD with NADPH in the presence of the aromatic substrate; and (ii) the

A Soluble Flavoprotein Contributes to Chromate Reduction and

reducing enzymes. As a prelude to this we report on some of the relevant characteristics of a soluble flavoprotein ofP. putida that contributes to chromate reduction and toler-ance in this bacterium. Materials and Methods Bacterial Strains, Media and Plasmids The following bacterial strains were employed in this study:Pseudomonas putidaKT2440

Mechanisms of cytochrome P‐450 catalysis

different enzymes. Oxygen surrogates have been used with P-450 enzymes, and studies with oxygen atom donors have been particularly useful in ruling out potential mechanisms involving dioxygen species. Groves first used a biomimetic porphyrin model to study P-450 reactions, and considerable literature in the area has accrued (for reviews see

University of Groningen Identification and characterization

for a cascade reaction with fused enzymes compared to the equimolar combination of separate enzymes40. The ADH-BVMO cascade system has been previously studied for the optimization of the biocatalytic conversion of cyclohexanol into ε-caprolactone (Figure 1)34,41. However, the reaction design is not trivial and some critical parameters are

By: Inaam A. Ameen

derive energy in the form of ATP from the controlled reaction of hydrogen with oxygen to form water. molecular oxygen is incorporated into a variety of substrates by enzymes known as oxygenases; many drugs, pollutants, and chemical carcinogens (xenobiotics) are metabolized by enzymes of this class, known as the cytochrome P450 system.

Oxidative stress and antioxidative system in plants

2. Direct reduction of oxygen to superoxide anions in may limit the reaction, but ferric ion can be recycled to the flavoprotein region of NADH dehydrogenase reduced ferrous state by reducing agents such as 02~. segment of the respiratory chain. The component ^ 2 responsible is likely to be the flavoprotein (of either Fe + 02 02 + Fe

Cyanobacterial Oxygenic Photosynthesis is Protected by

enzymes sharing sequence similarity. FDPs have been found mainly in anaerobic and some aerobic prokaryotes (Bacteria including cyanobacteria, and Archaea), and in Protozoa. Data mining of sequenced genomes has also led to the discovery of FDP homologs in some photosynthetic eukaryotes [2,3].

On the Oxygen Reactivity of Flavoprotein Oxidases

Scheme 2. The first half-reaction is the reduction of the flavin via hydride transfer from the alcohol (the reductive half-reac-tion), and the second half-reaction is the oxidation of the reduced flavin by molecular oxygen, the final acceptor (oxida-tive half-reaction) (4). CO is a useful biotechnological tool used for the determina-

Evolutionary Aspects and Regulation of Tetrapyrrole

Mar 30, 2015 Enzymes that operate mainly under microoxic conditions and the transcription of the genes encoding these upregulated enzymes are shown in blue. Enzymes that require oxygen for catalysis are shown by O2 in the red background, and enzymes that are inactivated by oxygen are shown by red x-O2 symbols.

Archives of Biochemistry and Biophysics

Oct 05, 2020 Dehalogenation reactions by flavin-dependent enzymes that replace a halogen with a hydroxyl group originating from oxygen include single and two-component systems [25]. These enzyme systems have bene isolated from aerobic bacteria and have been shown to degrade halo-genated aromatic compounds (HAC) [26]. The reaction requires

Introduction: Flavoprotein structure and mechanism

Introduction: Flavoprotein st VINCENT MASSEY Department of Biological Chemistr University of ifuctuie and m4anisrn. 1ichigan, Ann Arbor, Michigan 81O9. USA #{149} #{149} UNDERSTANDING OF THE vERsATILE chemistry of flavins and the mechanisms of action of flavoprotein enzymes has progressed enormously in the last 10 years, especially since

Formation and detoxification of reactive oxygen species

Xanthine oxidase is a flavoprotein containing two mole-cules of FAD, two molybdenum ions (VI), and eight iron ions in iron-sulfur centers [17]. During the course of the catalyzed reaction, two electrons are transferred from the substrate through the flavin coenzyme and iron-sulfur cen-ters to molecular oxygen. Hydrogen peroxide is generated

Dehydrogenation Mechanism in Flavoprotein Catalysis

This type of reaction should be differentiated from the oxygenase reaction, in which the substrate electrons are transferred directly to oxygen. The limiting chemical step of the dehydrogenation, i.e., the rupture of the kinetically stable substrate C-Hbond, is catalyzed by enzymes which have either pyridine