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. [sulfur carrier]-H + L-cysteine = [sulfur carrier]-SH + L-alanine AH2 + L-selenocysteine = A + H(+) + hydrogenselenide + L-alanine Cofactor biosynthesis; iron-sulfur cluster biosynthesis. Homodimer. 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. Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. Csd subfamily.