sulfoxidase

Sulfoxidase is a descriptive term for enzymes that catalyze the oxidation of sulfides (thioethers) to sulfoxides. It is not a single, formally defined enzyme family in the IUBMB nomenclature; rather, it covers a range of enzymes from different families that can introduce one oxygen atom into a sulfide substrate. The overall reaction, when viewed in a monooxygenase context, can be written as a sulfide plus molecular oxygen and a reducing partner yielding a sulfoxide, plus water and the oxidized cofactor. Some systems can also operate with hydrogen peroxide as the oxidant, producing the sulfoxide directly.

Enzymes described as sulfoxidases may include flavin-dependent monooxygenases and cytochrome P450s, among others. These enzymes often require cofactors such as flavin adenine dinucleotide (FAD) or NAD(P)H and molecular oxygen to insert oxygen into the sulfur atom of the substrate. Mechanistic diversity exists, but the common feature is the formation of a sulfoxide (R-S(=O)-R') from a sulfide. Some sulfoxidases can produce enantioenriched sulfoxides, which are valuable in asymmetric synthesis.

Occurrence and applications: sulfoxidases have been identified in various microorganisms, including bacteria and fungi, and are exploited in biocatalysis for the production of sulfoxides, especially enantiomerically pure compounds used in pharmaceuticals and agrochemicals. The term is often used in this biotechnological context rather than as a precise taxonomic designation.

See also: sulfoxide, sulfoxidation, enzyme nomenclature, biocatalysis, enantioselective oxidation.