L-cysteine + O2 = 3-sulfino-L-alanine + H(+) Binds 1 Fe cation per subunit. Optimum pH is 6.2. Up-regulated upon sporulation. Although there are Cys and Trp residues in equivalent positions with the residues forming a thioether cross-link in the eukaryotic homologous sequences, no thioether cross-link is formed in this protein. Belongs to the cysteine dioxygenase family.