Cysteine desulfurases mobilize the sulfur from L-cysteine to yield L-alanine, an essential step in sulfur metabolism for biosynthesis of a variety of sulfur-containing biomolecules. Component of the suf operon, which is activated and required under specific conditions such as oxidative stress and iron limitation. Acts as a potent selenocysteine lyase in vitro, that mobilizes selenium from L-selenocysteine. Selenocysteine lyase activity is however unsure in vivo. Can also desulfinate L-cysteine sulfinate (3-sulfino-L-alanine). [sulfur carrier]-H + L-cysteine = [sulfur carrier]-SH + L-alanine AH2 + L-selenocysteine = A + H(+) + hydrogenselenide + L-alanine 3-sulfino-L-alanine + H2O = H(+) + L-alanine + sulfite Displays a strong preference for selenocysteine as a substrate in vitro and is only very slightly active using cysteine. The interactions with SufE and the SufBCD complex act synergistically to enhance, up to 50-fold, its cysteine desulfurase activity. Cofactor biosynthesis; iron-sulfur cluster biosynthesis. Homodimer (PubMed:10329673). Interacts with SufE and the SufBCD complex composed of SufB, SufC and SufD. The interaction with SufE is required to mediate the direct transfer of the sulfur atom from the S-sulfanylcysteine. Suf operon is under both the Fe-dependent Fur repressor and the oxidative stress dependent OxyR activator. Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. Csd subfamily.