Cysteine dioxygenase (CDO, CAS number: 37256-59-0) is a mammalian non-heme iron enzyme that catalyzes the conversion of L-cysteine to cysteine sulfinic acid (cysteine sulfinate) by incorporation of dioxygen.
Cysteine sulfinic acid lies at a branch-point in cysteine catabolism, where it can follow two pathways resulting in the formation of taurine or sulfate. The cysteine sulfinic acid-dependent pathway of taurine metabolism follows the synthesis of hypotaurine (2-aminoethane sulfinate), which is subsequently oxidized to taurine. Also, cysteine sulfinate can undergo transamination to form β-sulfinylpyruvate, decomposing to form pyruvate and sulfite.