OXIDASE

Oxidase is a term used for enzymes in the class of oxidoreductases that catalyze oxidation of an organic or inorganic substrate using molecular oxygen as the terminal electron acceptor. In many cases the reaction reduces O2 to water or hydrogen peroxide. Oxidases are widespread in all forms of life and are often metal-containing or flavin-dependent.

Examples include cytochrome c oxidase, the terminal enzyme of aerobic respiration in mitochondria, which reduces O2 to water; glucose oxidase, a flavin-dependent enzyme used in food processing and biosensors; xanthine oxidase, which acts on purines to yield uric acid and hydrogen peroxide; and various polyphenol oxidases involved in plant browning and defense. Some oxidases, such as lactate oxidase, also play roles in metabolism and signaling.

Distinction from oxygenases: Oxidases transfer electrons from their substrate directly to molecular oxygen, whereas oxygenases introduce one or more atoms of oxygen into substrates. The latter category includes monooxygenases and dioxygenases, and they are mechanistically distinct from classic oxidases, though both are part of the broader family of oxygen-utilizing oxidoreductases.

Biological and practical importance: In organisms, oxidases contribute to energy production, detoxification, pigment formation, and defense responses. In industry and medicine, oxidases are used in biosensors (for example, glucose oxidase in glucose meters), biocatalysis, and diagnostic tests that rely on oxygen consumption or hydrogen peroxide production.