Abstract: Trypsin was used in catalysing the coupling between desalanine-B30-insulin(DAI) and Thr(Bu)OBu, DAI was obtained by digestion of porcine insulin with carboxypeptidase A. Thr(Bu)OBu was directly synthesized without N-terminal protection, different from general way and a high yield of human insulin was obtained. The purity of the semi-synthetic human insulin was one band of electrophoresis. It can be easily crystallized. The amino acid analysis of the semi-synthetic human insulin was identical with the theoretical value. The radiation inactivation test shows the semi-synthetic human insulin has the same insulin-binding activity with the porcine insulin.

Key words: Insulin, Trypsin, Semi-synthesis, Carboxypeptidase A