Oxidase

In biochemistry, an oxidase is an oxidoreductase (any enzyme that catalyzes a redox reaction) that uses dioxygen (O₂) as the electron acceptor. In reactions involving donation of a hydrogen atom, oxygen is reduced to water (H₂O) or hydrogen peroxide (H₂O₂). Some oxidation reactions, such as those involving monoamine oxidase or xanthine oxidase, typically do not involve free molecular oxygen.^[1]^[2]

The oxidases are a subclass of the oxidoreductases. The use of dioxygen is the only unifying feature; in the EC classification, these enzymes are scattered in many categories.

Examples

An important example is EC 7.1.1.9 cytochrome c oxidase, the key enzyme that allows the body to employ oxygen in the generation of energy and the final component of the electron transfer chain. Other examples are:

EC 1.1.3.4 Glucose oxidase
EC 1.4.3.4 Monoamine oxidase
EC 1.14.-.- Cytochrome P450 oxidase
EC 1.6.3.1 NADPH oxidase
EC 1.17.3.2 Xanthine oxidase
EC 1.1.3.8 L-gulonolactone oxidase
EC 1.10.3.2 Laccase
EC 1.4.3.13 Lysyl oxidase
EC 1.10.3.2 Polyphenol oxidase
Sulfhydryl oxidase. This enzyme oxidises thiol groups.

Oxidase test

In microbiology, the oxidase test is used as a phenotypic characteristic for the identification of bacterial strains; it determines whether a given bacterium produces cytochrome oxidases (and therefore utilizes oxygen with an electron transfer chain).

The test is used to determine whether a bacterium is an aerobe or anaerobe. However a bacterium that is oxidase negative is not necessarily anaerobic, it may just indicate the bacterium does not possess cytochrome c oxidase.

References

^ Eric J. Toone (2006). Advances in Enzymology and Related Areas of Molecular Biology, Protein Evolution (Volume 75 ed.). Wiley-Interscience. ISBN 978-0471205036.
^ Nicholas C. Price; Lewis Stevens (1999). Fundamentals of Enzymology: The Cell and Molecular Biology of Catalytic Proteins (Third ed.). USA: Oxford University Press. ISBN 978-0198502296.

External links

Catalase & Oxidase tests video
Oxidase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

[1] Eric J. Toone (2006). Advances in Enzymology and Related Areas of Molecular Biology, Protein Evolution (Volume 75 ed.). Wiley-Interscience. ISBN 978-0471205036.

[2] Nicholas C. Price; Lewis Stevens (1999). Fundamentals of Enzymology: The Cell and Molecular Biology of Catalytic Proteins (Third ed.). USA: Oxford University Press. ISBN 978-0198502296.

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v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)