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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.


An important example is EC 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:

Oxidase test[edit]

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, instead showing the bacterium does not possess cytochrome c oxidase.


  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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