β-Glucosidase from rumen liquor. Preparation, assay and kinetics of action

Publisher Website
Google Scholar
Abstract
A beta-glucosidase preparation, essentially microbial in origin, was obtained as a cell-free extract from sheep rumen contents, and its properties were investigated using o-nitro-phenyl beta-D-glucoside as substrate. The preparation has 2 pH optima, at 5.4 and 5.8, respectively. A value of 0.86 mM was obtained for Km, the dissociation constant of the enzyme-substrate complex for o-nitrophenyl beta-D-glucoside. The enzyme is stable between pH 5 and 7, and is stable at the temperature of assay, 37[degree], for 4 hours. Both glucono-1:4-lactone and glucono-l:5-lactone are strong competitive inhibitors of rumen beta-glucosidase activity, having an affinity for the enzyme about 10 times that of o-nitrophenyl beta-D-glucoside. Gluconic acid has no appreciable inhibitory effect. The changes in inhibitory power of the 2 lactones in aqueous solution at room temperature and 100[degree] can be correlated with the structural changes occurring in the lactones.