Cysteine dioxygenase (CDO1) is a mammalian non-heme iron enzyme that initiates several important metabolic pathways related to pyruvate and several sulfurate compounds including sulfate, hypotaurine and taurine. This protein catalyzes the conversion of L-cysteine to cysteine sulfinic acid (cysteine sulfinate) by incorporation of dioxygen. CDO1 is critical regulator of cellular cysteine concentrations and has an important role in maintaining the hepatic concentration of intracellular free cysteine within a proper narrow range.