Biosynthesis and Secretion of Yeast Invertase

The effect of cycloheximide and 2‐deoxy‐d‐glucose on the synthesis and secretion of invertase by yeast cells and protoplasts has been studied. Two yeast strains were used: Saccharomyces 303‐67, whose investase synthesis is repressed by glucose, and a mutant of it, Saccharomyces FH4C, which is only partially affected by high levels of glucose in the incubation media. For both strains the optimum glucose concentration is approximately 10 mM. Cycloheximide inhibited the synthesis of invertase in cells and protoplasts. The secretion of the enzyme by the protoplasts was inhibited to a similar extent. Parallel results were obtained with 2‐deoxy‐d‐glucose. Two forms of invertase are present in yeast protoplasts; a light form devoid of carbohydrate and a heavy form which contains carbohydrate and is readily secreted. In all experimental conditions studied the relative amount of both forms remained constant. This indicates that although cycloheximide and 2‐deoxy‐d‐glucose exert their action at two different points in the biosynthesis of glycoproteins, either of them can stop the process of synthesis and secretion of yeast invertase.