Acylation of peptide hydroxyl groups with the Bolton-Hunter reagent

Reaction of the decapeptide gonadotropin releasing hormone (GnRH) with the Bolton-Hunter reagent produced a single major derivative. Mass spectrometric analysis of this derivative at M-Scan Corporation revealed that O-acylation of the Ser⁴ hydroxyl had occurred. Formation of the O-acylated Ser⁴ derivative was dependent on the presence of the His² residue in GnRH. Similar experiments with several unrelated peptides revealed that the Bolton-Hunter reagent will readily acylate hydroxyl groups on serine, tyrosine, and threonine side chains located two positions from a histidine residue (e.g., His-X-Ser). Such O-acylated peptides can be formed under mild reaction conditions and appear to be relatively stable. Recognition of this sequence-specific O-acylation can be critical when labeling peptides with the Bolton-Hunter reagent and when interpreting experiments in which such modified peptides are used.