ISSN:
0006-3525
Keywords:
peptide bond cleavage
;
asparagine deamidation
;
succinimide ring formation
;
kinetics and mechanism
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The cleavage reaction of the peptide bond next to the Asn residue has been studied in the pH range 7.4-13.8 at 37°C and μ = 1M. This reaction yields an N-terminal peptide fragment having at its C-terminus a succinimide ring, which rapidly hydrolyses to both asparagine and iso-asparagine residues.For both the two consecutive reactions, peptide bond cleavage and the succinimide hydrolysis, the general trend is an increase of the reaction rate with the pH. However, for the hydrolysis reaction there is a small decrease in the pH range 10-11 caused by the deprotonation of the succinimide nitrogen atom. Kinetic evidence indicates that the cleavage reaction is a multistep process with a change in the rate-determining step at pH 8.5-9.0. The mechanism involves preequilibrium deprotonation of the NH2 amide group of the Asn side chain, followed by nucleophilic attack of the nitrogen atom on the carbonyl carbon atom of the same asparagine residue, giving a cyclic intermediate. Then, general acid-catalyzed departure of the leaving group gives the final reaction product. At pH 〈 8.5, the formation of the cyclic intermediate is rate determining, whereas, at higher pH, it is the departure of the leaving group. © 1997 John Wiley & Sons, Inc. Biopoly 40: 543-551, 1996
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
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