Mouse α-amylase synthesized by Saccharomyces cerevisiae is released into the culture medium

Abstract

A cDNA segment complementary to the mouse salivary amylase messenger RNA has been inserted into the yeast expression vector pMA 56 behind the promoter of the gene encoding the alcohol dehydrogenase I of yeast. Yeast transformants containing plasmids with the normal orientation of the promoter and the mouse α-amylase cDNA gene produce amylase and release the enzyme in free form into the medium. In one litre cultures with a final cell density of 2·107 cells ml−1 75 μ of amylase is found corresponding to 0.1% of the cell protein. It has been estimated that almost 90% of the amylase synthesized by the cells is excreted. A handy plate assay for colonies excreting α-amylase is described.