Yeast β-glucosidase: Comparison of the physical-chemical properties of purified constitutive and inducible enzyme

Abstract

A constitutive β-glucosidase has been purified about 200-fold from the yeast hybrid Saccharomyces dobzhanskii X Saccharomyces fragilis. The purified enzyme was homogeneous to electrophoresis and ultracentrifugation. The physical-chemical properties of the enzyme are described and compared with those of an inducible β-glucosidase of Rhodotorula minute. The two enzymes were indistinguishable with the exception of their behavior toward natural β-glucosides. The affinity constants of these β-glucosides were ten times higher for the constitutive enzyme than for the inducible enzyme. At saturating substrate concentrations, the rates of hydrolysis were the same for both enzymes. The data suggest that the two enzymes differ in the nature of a group(s) in close proximity to the catalytic site.