Peptide kinetics. Part 12.—The effect of Zn(II) on the reaction of some glycine-containing dipeptides and substituted diketopiperazines at pH 5.6 and 368.2 K

The kinetics of the simultaneous reactions of sequence inversion of a dipeptide pair AB, BA through the diketopiperazine intermediate [graphic omitted] and hydrolysis of the dipeptide pair to give amino acids A and B have been investigated for the following systems: glycyl-L-leucine, L-leucyl-glycine, glycyl-L-leucine diketopiperazine; glycyl-L-alanine, L-alanyl-glycine, glycine-L-alanine diketopiperazine; glycyl-glycine and glycyl-glycine diketopiperazine at pH 5.6 and 368.2 K in the presence and absence of Zn(II) ions. Zn(II) ions catalyze all the reactions involved including the formation of the diketopiperazines and their cleavage. Suggestions are made concerning the role of the Zn(II) ions in these reactions.