Ammonia cleaves polypeptides at asparagine proline bonds.
Polypeptides that contain the sequence Asn-Pro undergo complete cleavage at this amide bond with ammonia. One cleavage product possesses Pro as the new amino terminus and the other Asn or isoAsn as the new C-terminus, the formation of the latter probably arising by way of a cyclic succinimide intermediate. Other Asn-X bonds where X = Tyr, Gln, Ile, Glu, Ala, Gly, Asn or Phe did not exhibit any peptide bond cleavage, whereas when X = Leu, Thr and Ser partial cleavage was observed. Asn residues not involved in chain-cleavage underwent deamidation to Asp as shown by MALDI-ToF mass spectrometry (MS) analysis. The partial conversion of in-chain Asp residues to isoAsp under the reaction conditions was inferred from RP-HPLC and MS analysis of reaction mixtures.
Tarelli
E
E
Medical Biomics Centre, St George's Hospital Medical School, London, UK. etarelli@sghms.ac.uk
Corran
P H
PH
D000595:Amino Acid Sequence; D000641:Ammonia / Q000737:chemistry*; D000818:Animals; D001216:Asparagine / Q000737:chemistry*; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009478:Neuropeptide Y / Q000737:chemistry; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D011392:Proline / Q000737:chemistry*
D009478:Neuropeptide Y; D010446:Peptide Fragments; D010455:Peptides; D001216:Asparagine; D000641:Ammonia; D011392:Proline