δ‐l‐(α‐Aminoadipoyl)‐l‐cysteinyl‐d‐valine synthetase: isolation of l‐cysteinyl‐d‐valine, a ‘shunt’ product, and implications for the order of peptide bond formation

Dipeptide synthesis by an isolated adenylate‐forming domain of non‐ribosomal peptide synthetases (NRPS)

“…Peptide bond formation occurs in an amino→carboxy‐terminal elongation reaction supported by the condensation domain. This ‘thiotemplate mechanism’ has recently been questioned by Shiau et al [3,4] having shown the synthesis of dipeptides, L ‐ O ‐(methylserinyl)‐ L ‐valine and L ‐ O ‐(methylserinyl)‐ D ‐valine, by δ‐( L ‐α‐aminoadipyl)‐ L ‐cysteinyl‐ D ‐valine synthetase (ACVS). Employing 18 O‐labelled amino acids, the maintenance of label in the carboxyl group indicates direct aminolysis of the mixed anhydride intermediate.…”

Active site titration of gramicidin S synthetase 2: evidence for misactivation and editing in non‐ribosomal peptide biosynthesis

“…Decomposition may be in part the result of abortive side reactions, such as the formation of dipeptides from active aminoacyl adenylates. Small but detectable amounts of dipeptides, such as L,D ‐cisteinyl‐valine and L ‐O‐(methylserinyl)‐ L ‐valine, are formed by ACV synthetase from interaction of an enzyme bound acyladenylate and an amino group of a free amino acid without the involvement of an activated intermediate thioester moiety [18–21]. The dipeptides were detected in solution as ‘shunt’ products and not as enzyme bound intermediates.…”

Penicillin biosynthesis: intermediates of biosynthesis of δ‐l‐α‐aminoadipyl‐l‐cysteinyl‐d‐valine formed by ACV synthetase from Acremonium chrysogenum

“…Recently Shiau et al recovered O ‐methyl‐seryl‐ d , l ‐valine and l ‐cysteinyl‐ d ‐valine in attempts to replace cysteine by O ‐methyl‐ l ‐serine and aminoadipic acid by glutamic acid, respectively [9, 10]. These dipeptides were formed in small amounts, while the respective tripeptides have not been detected.…”