In enzymology, a thiol oxidase () is an enzyme that catalyzes the chemical reaction 4 R'C(R)SH + O2 2 R'C(R)S-S(R)CR' + 2 H2O Thus, the two substrates of this enzyme are R'C(R)SH and O2, whereas its two products are R'C(R)S-S(R)CR' and H2O. This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with oxygen as acceptor. The systematic name of this enzyme class is thiol:oxygen oxidoreductase. This enzyme is also called sulfhydryl oxidase. References EC 1.8.3 Enzymes of unknown structure