Secretory expression of α single-chain insulin precursor in yeast and its conversion into human insulin

A synthetic single-chain porcine insulin precursor (PIP) gene and an α-mating factor leader sequence (αMFL) gene obtained by the PCR method are inserted between the promoter and 3'-terminating sequence of the alcohol dehydrogenase gene ADH1 in plasmid pVT102-U to form plasmid pVT102-U/α MFL-PIP. The single-chain insulin precursor is expressed and secreted to the culture medium by Saccharomyces cererisiae transformed by pVT102-U/αMFL-PIP. The precursor is purified and converted into human insulin by tryptic transpeptidation. The purified human insulin is fully active and can be crystallized. The overall yield of human insulin is 25 mg per liter of culture medium.