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(2+) cation per subunit. Zn(2+) can be used to a much lesser extent (PubMed:17135237). Ni(2+) can be used to a lesser extent (By similarity). Organosulfur biosynthesis; taurine biosynthesis; hypotaurine from L-cysteine: step 1/2. Monomer. Highly expressed in liver and placenta. Low expression in heart, brain and pancreas. Also detected in hepatoblastoma Hep-G2 cells. In hepatoblastoma Hep-G2 cells, down-regulated by phorbol 12-myristate 13-acetate (PMA). 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.