What is Succinimide

Non-enzymatic intramolecular reactions can lead to deamidation and isomerisation racemization of proteins and peptides and asparaginyl aspartyl succinimide via intermediaries. To understand the dependence of the sequence of these reactions was measured succinimide formation rate in a number of synthetic peptides at pH 7.4. These peptides (Val-Tyr-Pro-X-Y-Ala) containing an internal aspartyl ester group, asparaginyl, aspartyl ester beta-methyl or aspartyl alpha-methyl (X), followed by a glycyl residue, seryl or alanyl (Y). The succinimide asparaginyl peptides forming rate were judged 13.1 35.6 times faster than that of aspartyl peptides. The peptides forming speed glycyl succinimide were 6.5 to 17.6 times faster than that of alanyl peptides, while the peptides of seryl rate 1.6 to 4.5 times were faster than those alanyl peptides. The entire 232 times in these reaction rates for aspartyl and asparaginyl residues suggests that the sequence may be an important factor in the stability of the peptides in the hoses. In proteins, it may be a much larger area in the formation rate succinimide because some conformations can greatly enhance or inhibit this reaction.