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δ‐ L ‐(α‐Aminoadipoyl)‐ L ‐cysteinyl‐ D ‐valine synthetase: the order of peptide bond formation and timing of the epimerisation reaction
Author(s) -
Shiau Chia-Yang,
Baldwin Jack E.,
Byford Michael F.,
Sobey Wendy J.,
Schofield Christopher J.
Publication year - 1995
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)01320-z
Subject(s) - chemistry , valine , tripeptide , electrospray ionization , peptide bond , stereochemistry , peptide , cysteine , biosynthesis , amino acid , biochemistry , mass spectrometry , enzyme , chromatography
δ‐ L (α‐Aminoadipoyl)‐ L ‐cysteinyl‐ D ‐valine (ACV) synthetase catalyses the formation of the common precursor tripeptide of both the penicillin and cephalosporin antibiotics from the l ‐enantiomers of its constituent amino acids. Replacement of cysteine with l ‐ O ‐methylserine in preparative‐scale incubations led to the isolation of both t.‐O‐methylserinyl‐ L ‐valine and l ‐ O ‐methylserinyl‐ D ‐valine dipeptides. The dipeptides were characterized with the aid of authentic synthetic standards by both 1 H NMR and electrospray ionization MS. A revised mechanism for ACV biosynthesis involving formation of the cysteinyl‐valine peptide bond before the epimerisation of valine and subsequent condensation with the δ‐carboxyl of L ‐α‐aminoadipate is therefore proposed.