ABSTRACT
The first protease-mediated preparation of partially synthetic human insulin was described by Inouye et al. The tryptic semisyntheses of insulin discussed so far employ intermolecular reactions in which peptide bond formation is encouraged by the presence of a considerable molar excess of the respective amine component. Thus after tryptic cleavage of the Arg-Gly bond the molecule was prevented from falling apart by the presence of the carbonyl-b/s-methionyl cross-link between the A- and B-chains. As millions of diabetics suffer from an insulin deficiency, there exists a strong demand for human insulin. The protease-catalyzed substitution of the specificity-controlling Lys15 residue of bovine trypsin-kallikrein inhibitor by respectively arginine, phenylalanine, and tryptophan, has been described by Jering and Tschesche. Promising results have also been reported for the protease-catalyzed semisynthesis of cytochrome c analogs. The specificity of this protease is strictly confined to peptide bonds the carbonyl group of which is contributed by a lysine residue.
