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

Main article: 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

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.

External links

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