Wikipedia
O-Acetylserine
O-Acetylserine is the α- amino acid with the chemical formula HOCCH(NH)CHOC(O)CH. It is an intermediate in the biosynthesis of the common amino acid cysteine in bacteria and plants. O-Acetylserine is biosynthesized by acetylation of the serine by the enzyme serine transacetylase. The enzyme O-acetylserine (thiol)-lyase, using sulfide sources, converts this ester into cysteine, releasing acetate:
HOCCH(NH)CHOH → HOCCH(NH)CHOC(O)CH HOCCH(NH)CHOC(O)CH → HOCCH(NH)CHSH