Purification and Properties of an Inducible p-Glucosidase of Yeast*

In the past decade considerable advances have been achieved in the study of induced enzyme biosynthesis in microorganisms. A comparison of three of the better studied systems, P-galactosidase in Escherichia coli (l), penicillinase in Bacillus cereus (2), and oc-glucosidase in Xaccharomyces cerevisiae (3) indicates that there are a number of differences in these inductions. In order to compare further several inducible systems within the same group of organisms, a search was undertaken for a second inducible system in yeast. The wide distribution of /3-glucosidase among plants (4), fungi (5), and yeasts (6) suggested this enzyme as a possible system for examination. Among the yeasts, the capacity of intact cells to hydrolyze P-glucosides varies both with the strain and conditions of growth (6). For example, Candida tropicalis NCYC4 hydrolyzes salicin but not arbutin, whereas several strains of X. cerevisiae are active on arbutin but weak on salicin. Since observations of this type can be interpreted as evidence for several fi-glucosidases, as has been demonstrated in fungi (7), or stereospecific permeation systems (8)) further purification and study of the purified enzymes or enzymes of yeast are indicated. Neuberg and Hofmann (9) have partially purified a fl-glucosidase from plasmolyzed yeast by ethanol-diethyl ether precipitation and examined some of its properties. A thermolabile enzyme, which is active against esculin, has been reported in bakers’ yeast (10). The demonstration of an inducible fi-glucosidase in S. cerevisiae strain Yeast Foam (11) has led us to examine this enzyme further. As a prerequisite to an interpretation of the induction experiments, it was necessary not only to purify the enzyme and examine its specificity but also to provide a basis for quantitative determination of the enzyme content of the organism under various conditions.