Deamidation via cyclic imide in asparaginyl peptides.
The deamidation reaction of asparaginyl peptides was studied as a function of the pH and sequence. The deamidation of Boc-Asn-Gly-Gly-NH2 and the hydrolysis of the corresponding aminosuccinyl (Asu) peptide, Boc-Asu-Gly-Gly-NH2, were carried out in the pH ranges 5-10, whereas the deamidation of Boc-Asn-Ala-Gly-NH2, Boc-Asn-Gly-Ala-NH2 and Boc-Asn-Ser-Gly-NH2 was studied at pH 8.9 only. In each case, the conversion of the amide side-chain moiety of the Asn to carboxyl group occurs via a succinimide intermediate (Asu), and its breakdown leads to a normal and an isoaspartyl peptide. The kinetic constants of the Asu formation and the hydrolytic step increase markedly at basic pH. The influence of the side chain of the residue next to Asn is also discussed.
Capasso
S
S
Dipartimento di Chimica, Università di Napoli, Italy.
Mazzarella
L
L
Sica
F
F
Zagari
A
A
D000577:Amides; D000595:Amino Acid Sequence; D001216:Asparagine; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007094:Imides; D007700:Kinetics; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry*
D000577:Amides; D007094:Imides; D009842:Oligopeptides; D010455:Peptides; D001216:Asparagine