ABSTRACT
The enzymes catalyzing the processes in which peptide synthetic chemists are most interested are the proteases. Although commonly known for their proteolytic action, they obey, in common with all other biocatalysts, the principle of microscopic reversibility. As a consequence, proteases accelerate both the forward and the reverse reaction of the protease-specific chemical processes to the same degree. The "chemistry" of chymotryptic catalysis not only provides an insight into the mode of action of proteases but it also describes the factors essential for the catalytic efficiency of an enzyme. Proteases which possibly favor this mechanism are pepsin, carboxy-peptidase A and, cum grano salis, thermolysin. The principle of carboxyl activation is ubiquitious in the field of peptide or protein synthesis both in vivo and in vitro. Consequently, the activation energy for the acyl transfer would be reduced and the reaction would proceed more rapidly.
