Dehydrogenase oxidases

Oxidoreduciases. Enzymes catalysing redox reactions. The substrate which is oxidized is regarded as the hydrogen donor. This group includes the trivially named enzymes, dehydrogenases, oxidases, reductases, peroxidases, hydrogenases and hydroxylases. 

Oxoreductases include enzymes such as dehydrogenases, oxidases and peroxidases which catalyse transformations such as oxidation of alcohols to carbonyls and dehydrogenation of functionalized alkanes to alkenes. 

This correlated with a 64% decrease in endogenous hepatic xanthine dehydrogenase/oxidase activity. 

Oxidoreductases dehydrogenase, oxidase oxygenase, peroxidase oxidation or reduction... 

Figure 8.6 The three dehydrogenase (oxidase) reactions in amino acid degradation. The enzymes are D-amino acid oxidase, glutamate dehydrogenase and proline oxidase (dehydrogenase). Biochemical details are given in Appendix 8.4.

NADPH v malate, dehydrogenaseX nadpM alanine proline dehydrogenase (oxidase) FAD SfADHj... 

Flavins are very versatile redox coenzymes. Flavopro-teins are dehydrogenases, oxidases, and oxygenases that catalyze a variety of reactions on an equal variety of substrate types. Since these classes of enzymes do not consist exclusively of flavoproteins, it is difficult to define catalytic specificity for flavins. Biological electron acceptors and donors in flavin-mediated reactions can be two-electron acceptors, such as NAD+ or NADP+, or a variety of one-electron acceptor systems, such as cytochromes (Fe2+/ Fe3+) and quinones, and molecular oxygen is an electron acceptor for flavoprotein oxidases as well as the source of oxygen for oxygenases. The only obviously common aspect of flavin-dependent reactions is that all are redox reactions. 

J. Wang, M.P. Chatrathi and B. Tian, Microseparation chips for performing multienzymatic dehydrogenase/oxidase assays Simultaneous electrochemical measurement of ethanol and glucose, Anal. Chem., 73 (2001) 1296-1300. 

Soon after the initial discovery, it became apparent that neither the source of the enzyme, nor the type of enzyme, nor the type of solvent seem to constrain the use of organic solvents (Zaks, 1986a). Various types of enzymes, such as lipases, proteases (chymotrypsin, subtilisin), oxidoreductases (alcohol dehydrogenase, oxidases, and peroxidases), and others, react in organic solvents. A selection of enzymes... 

Enantioselective oxidation of racemic alcohols as well as reduction of racemic ketones and aldehydes have been widely applied to obtain optically active alcohols.25 27 The enzymes catalyzing these reactions are alcohol dehydrogenase, oxidases, and reductases etc. Coenzymes (NADH, NADPH, flavine etc) are usually necessary for theses enzymes. For example, for the oxidation of alcohols, NAD(P)+ are used. The hydride removed from the substrate is transferred to the coenzyme bound in the enzyme, as shown in Figure 24. There are four stereochemical patterns, but only three types of the enzymes are known. 

The oxidoreductase class of biocatalysts is one of the most common of all biological reactions, comprising dehydrogenases, oxidases, and reductases. All these enzymes act on substrates through the transfer of electrons with various co-factors or co-enzymes serving as acceptor molecules. Only a select group of reactions will be discussed because of space limitations, so the reader is referred to other texts for more in-depth discussions of other oxidation-reduction reactions.17 20 25-28... 

Enzymes are proteinaceous catalysts peculiar to living matter. Hundreds have been obtained in purified and crystalline form. Their catalytic efficiency is extremely high—one mole of a pure enzyme may catalyze the transformation of as many as 10,000 to 1,000,000 moles of substrate per minute. While some enzymes are highly specific for only one substrate, others can attack many related substrates. Avery broad classification of enzymes would include hydrolytic enzymes (esterases, proteases), phosphorylases, oxidoreductive enzymes (dehydrogenases, oxidases, peroxidases), transferring enzymes, decarboxylases and others. 

Class 1. Oxidoreductases catalyze oxidation and reduction reactions. They include the dehydrogenases, oxidases, reductases, peroxidases, oxygenases, hydroxylases, and catalases. 

The above schemes work reasonably well for certain enzyme reactions, especially for substrates where oxygen addition/loss occurs at a main group element (e.g., N, S, Se, Cl, see Table I). In addition to SO and nitrate reductase, key examples are DMSOR, trimethylamine oxide reductase, chlorate reductase, and selenate reductase. In the case of enzymes catalyzing C-based redox reactions of organic molecules, notably XDH and aldehyde oxidase, a direct OAT step is unlikely and is replaced by mechanistic steps typical of hydro-xylation (2). The essential features of the mechanism are shown in Fig. 10 for xanthine dehydrogenase/oxidase. 

Scrutton, N. S., 1994, a/p barrel evolution and the modular assembly of enzymes emerging trends in the flavin dehydrogenase/oxidase family, BioEssays 16 1159122. 

Oxireductases Dehydrogenases Oxidases Reductases Oxygenases Peroxidases Catalases Catalyze oxidation-reduction reactions. Important in fermentation and respiration pathways. 

Figure 1. Cofactors and prosthetic groups in dehydrogenases, oxidases, and monooxygenases.

Oxidoreductases Dehydrogenases Oxidases Reductases Introduction of double bond by removal of Ha Oxidation Reduction ... 

The thyroid also contains xanthine oxidase [48, 107]. In rats the thyroid has about 30% of liver enzyme activity, with a ratio of dehydrogenase oxidase levels of approximately 3 1 [ 130], As a result of in vitro experiments, Lee and Fischer reported that the hydrogen peroxide produced by the oxidase form of xanthine oxidase is required for the biosynthesis of thyroid hormones [48]. However, Japanese workers [130] who did find a suppression of thyroid... 

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