ACV synthetase (ACVS, ** L -δ-(α-aminoadipoyl)- L -cysteinyl- D -valine synthetase**, N-(5-amino-5-carboxypentanoyl)- L -cysteinyl- D -valine synthase, ) is an enzyme that catalyzes the chemical reaction The five substrates of this enzyme are ATP, L -2-aminohexanedioate, L -cysteine, L -valine, and H2O, whereas its three products are AMP, diphosphate, and N-[ L -5-amino-5-carboxypentanoyl]- L -cysteinyl- D -valine. ACVS is an example of a nonribosomal peptide synthetase (NRPS). It participates in penicillin and cephalosporin biosyntheses.