Semisynthesis of human insulin utilizing chemically modified carboxypeptidase Y

Abstract

It has previously been demonstrated that the C-terminal alanyl residue in the B-chain of porcine insulin can be exchanged with a threonyl residue in a carboxypeptidase Y catalyzed transpeptidation reaction using threonine amide as nucleophile. However, with this procedure the transpeptidation product, human insulin amide, was obtained in relatively low yields. In the present paper it is demonstrated that mercury halide derivatives of CPD-Y catalyze the transpeptidation reaction with porcine insulin effectively and human insulin amide could be isolated in high yield. It is also demonstrated that deamidation of human insulin amide to yield essentially homogeneous human insulin can be achieved using CPD-Y modified with methyl mercuric iodide (Me-Hg-CPD-Y).