Effects of proteolytic enzymes on invertase secretion in sphaeroplasts of Saccharomyces: inhibition by trypsin.

Exogenously added trypsin arrested invertase secretion by sphacroplasts of Saccharomyces strain 1016. The mechanism of inhibition is presumed due to attack on plasma membrane protein(s). Gross membrane damage by trypsin was not apparent, as evidence by the absence of leakage of intracellular alkaline phosphatase, after trypsin treatment. Trypsin treatment did induce an increased sensitivity to lysis, observed only when changes in osmotic pressure were made and fresh glucose added. While synthesis of invertase was eventually inhibited by trypsin, a greater than twofold increase in internal invertase was observed, due to complete inhibition of secretion. This is the first report of the uncoupling of synthesis and secretion in yeast.