Aminolysis of acyl-chymotrypsins by amino acids. Kinetic appearance of concentration effect in peptide yield enhancement by freezing.

The effects of reagent concentrations, various added substances, pH and temperature on the yield of peptide synthesis by chymotrypsin in frozen and liquid solutions at subzero temperatures have been studied. Increased nucleophile concentration in the liquid microinclusions of ice has been shown to be sufficient for explaining the peptide yield improvement found at freezing conditions.

Peptide synthesis by chymotrypsin in frozen solutions. Free amino acids as nucleophiles.

Nucleophilic efficiency of the free amino acids in chymotrypsin-catalyzed acyl transfer in ice at -18 degrees C using ethyl esters of N-maleyl-L-tyrosine and L-tyrosine as the acyl group donors has been studied. Although the amino acids did not act as acyl acceptors in liquid water, the high yields of peptides were obtained in frozen solutions at pH 10.5 (before freezing).