[Enzyme intermediates with the C-terminal products of substrate hydrolysis by carboxypeptidase A and chymotrypsin. Use of the free energy linearity principle].

Based on the correlation between the kinetics and free energy of enzymatic reactions of hydrolysis (i. e. free energy linearity principle) for peptide and ester substrate hydrolysis by carboxypeptidase A, the identity of the catalytic mechanism for these substrates and the lack of formation of an activated enzyme intermediate with the C-terminal part of the hydrolyzed substrate were demonstrated. Using the energy linearity principle to the hydrolysis of specific peptide substrates by chymotrypsin, the nature of the activated enzyme intermediate with the C-terminal part of the substrate as a complex with a non-ionized product can be postulated. This accounts for the transpeptidation (according to the amino transfer type) of the peptides with an unprotected carboxylic group. It was concluded that the formation of the enzyme intermediate with the C-terminal part of the hydrolyzed substrate for all the three main classes of proteinases, i. e. serine, carboxylic and metal enzymes, occurs via different mechanisms.