Catalyzes the oxidation of cysteine to cysteine sulfinic acid with addition of molecular dioxygen. L-cysteine + O2 = 3-sulfino-L-alanine + H(+) Binds 1 Fe cation per subunit (PubMed:16611640). Ni(2+) and Zn(2+) can be used to a lesser extent (By similarity). Organosulfur biosynthesis; taurine biosynthesis; hypotaurine from L-cysteine: step 1/2. Monomer. Highest levels in liver. Significant expression also in kidney, lung and brain. From neonate to weaning. By increase of sulfur amino acid intake. The thioether cross-link between Cys-93 and Tyr-157 plays a structural role through stabilizing the Fe(2+) ion, and prevents the production of highly damaging free hydroxyl radicals by holding the oxygen radical via hydroxyl hydrogen. Belongs to the cysteine dioxygenase family.