Influence of water-miscible solvents on hydrolytic activity of crude almond β-glucosidase

The influence of polar solvents on the hydrolysis of cellobiose (4-O-(β-d-glucopyranosyl)-β-d-glucopyranose) and p-NPG (p-nitrophenyl β-d-glucopyranoside) by crude almond β-glucosidase has been measured. THF and acetonitrile diminish the initial reaction rate by a factor of 2 at a concentration of 10%, while DMF, DMSO and 2-methyl-2-butanol have little effect at this concentration, but induce a decrease at higher concentrations. ecificity constant Vmax/KM of the crude enzyme in aqueous solution was 200-fold higher for p-NPG than for cellobiose, indicating that between the two β-glucosidase activities present in almond, prunasin hydrolase may be more important than amygdalin hydrolase. However, the specificity constant for p-NPG was more affected by the presence of DMF, since it dropped six-fold for a 20% concentration of solvent while in the case of cellobiose, the drop was only 1.6-fold for the same solvent concentration.