ABSTRACT
The impact of the regiospecific action of the proteases may be illustrated by the fact that 13 out of the 20 "codogenous" amino acids possess a third- or side-chain functionality. The primary specificity is mostly determined by a strong bias of the protease in favor of a single amino acid which can sometimes be replaced by different though structurally related amino acids; however, the position of these within the respective substrate is unequivocally defined. The most useful feature of the enzymatic approach to peptide synthetic chemistry is certainly its ability to provide — due to the stereospecific action of the proteases — for an outstanding way of maintaining the chirality or handedness of the reactants. In a peptide bond forming reaction, therefore, the ability of proteases to exert stereospecific control in their catalysis results in optically pure homochiral products, even though the starting material might have originally been an optically heterogeneous mixture.
