Has very low cyanoalanine synthase and cysteine synthase activities. hydrogen sulfide + O-acetyl-L-serine = acetate + L-cysteine hydrogen cyanide + L-cysteine = 3-cyano-L-alanine + H(+) + hydrogen sulfide Homodimer. Expressed in tubers, buds and leaves. Slightly down-regulated by ethylene treatment. No effect from wounding. Belongs to the cysteine synthase/cystathionine beta-synthase family.