ABSTRACT
In order to establish the enzymatic procedure as an integral part of the peptide synthetic methodology, one must inevitably reach beyond the scope of synthetic model peptides to a more generalized application of the proteases as biocatalysts for peptide synthetic purposes. The enzymatic assembly of the endogenous opioid peptides Leu- and Met-enkephalin, the amino acid sequences of which were described by Hughes et al. may represent the first example of the synthetic applicability of proteases to the preparation of naturally occurring peptides. During enzymatic peptide syntheses, this condition is also valid as far as the temporary protection of a-amino and a-carboxyl groups is concerned. The result of the enzymatic syntheses of the enkephalins clearly demonstrated the intrinsic capability of the proteases to function as biocatalysts for the preparation of biologically active peptides. The enzymatic synthesis of the C-terminal octapeptide amide of cholecystokinin represents a further example of the applicability of the proteases as catalysts in peptide synthetic chemistry.
