L-cysteine + O2 = 3-sulfino-L-alanine + H(+) Binds 1 Fe cation per subunit. Organosulfur biosynthesis; taurine biosynthesis; hypotaurine from L-cysteine: step 1/2. The thioether cross-link between Cys-85 and Tyr-149 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.