Oxidases

Oxidases are enzymes in the class of oxidoreductases that catalyze oxidation-reduction reactions with molecular oxygen as the final electron acceptor. In typical oxidase reactions, the substrate is oxidized and O2 is reduced, yielding water or hydrogen peroxide as a byproduct. Unlike oxygenases, oxidases do not insert oxygen atoms into the substrate.

Oxidases are diverse and can be organized by their cofactors and substrates. Flavin-containing oxidases use FAD or FMN as cofactors, examples being glucose oxidase and lactate oxidase. Heme-containing oxidases include cytochrome c oxidase, a key component of mitochondrial respiration, which reduces O2 to water while pumping protons. Copper-containing oxidases include tyrosinase, involved in melanin synthesis and plant browning.

Other examples include xanthine oxidase, urate oxidase, and amine oxidases such as monoamine oxidase, all of which channel electrons to O2 to form hydrogen peroxide or water. Many oxidases generate hydrogen peroxide, which can function in signaling or be detoxified by catalase and peroxidases. In plants and microorganisms, oxidases participate in defense mechanisms and pigment formation; clinically and industrially, oxidases are used in biosensing and analytical assays that detect substrates via the production of H2O2.

Classification: in enzyme nomenclature, oxidases are part of the oxidoreductases (EC 1) with oxygen as the electron acceptor, and the exact EC sub-subclass depends on substrate and cofactor. Their roles span energy metabolism, detoxification, biosynthesis, and industrial applications.