The Activating System of Chitin Synthetase from Saccharomyces cerevisiae

The protein inhibitor of the yeast protease which activates chitin synthetase zymogen has been purified from Saccharomyces cerevisiae. The protein appears to be homogeneous by disc gel electrophoresis and gel electrofocusing. The molecular weight of the inhibitor, as determined by gel filtration in the presence of 6 m guanidine hydrochloride, is estimated to be about 8500, with no evidence for the existence of subunits. Amino acid analysis shows the absence of cysteine, methionine, arginine, and tryptophan. The NH2-terminal residue is threonine. Comparison of the inhibitors from S. cerevisiae and Saccharomyces carlsbergensis revealed that both proteins are of equivalent molecular size but differ substantially in electrical charge.