coxidase

Coxidase (also written cooxidase or co-oxidase) is a term used in biochemistry and environmental microbiology to describe enzymes or enzyme systems that mediate co-oxidation reactions. It refers to a functional phenomenon rather than a single, uniform enzyme class. In many contexts, cooxidation occurs when an organism oxidizes a primary substrate for growth or energy and incidentally oxidizes a secondary substrate that is not used for growth.

In microbial metabolism, cooxidation or co-metabolism describes the process by which a non-growth substrate is transformed during the enzymatic processing of a growth substrate. This often involves oxidoreductases such as monooxygenases, dioxygenases, or certain cytochrome P450 systems that generate reactive oxygen species or activated oxygen species capable of attacking the secondary substrate. The secondary substrate is typically not essential for the organism's energy or carbon supply, and its oxidation may be inefficient or lead to a range of metabolites.

Applications and examples of cooxidase activity are commonly discussed in environmental biotechnology and bioremediation. Cooxidation enables the degradation of recalcitrant compounds such as polycyclic aromatic hydrocarbons, chlorinated solvents, and certain dyes when a readily metabolizable substrate is present. Enzymes including methane monooxygenase, toluene dioxygenase, and various peroxidases have been reported to exhibit cooxidase activity under appropriate conditions. Laccases with mediator systems can also effect co-oxidation of certain pollutants.

Limitations of cooxidation include low affinity for the secondary substrate, variable selectivity, and potential formation of toxic metabolites. Its effectiveness is influenced by environmental factors and the availability of suitable primary substrates. See also co-metabolism, monooxygenase, dioxygenase, oxidase.