A beta-glucosidase associated with cell walls from cell suspension cultures of carrot

The activity of beta-glucosidase (EC 3.2.1.21) in the protein fraction solubilized with 3 M LiCl from cell walls of carrot cell cultures was found to be much higher than those of the other glycan-hydrolases. The cell wall-associated beta-glucosidase was purified to electrophoretic homogeneity. The M(r) of the purified enzyme was estimated to be 46 000 by Sephacryl S-200HR gel-permeation, and 48 000-52 000 by SDS-PAGE under denaturing conditions. The enzyme contained carbohydrate and protein in a ratio of 1:15 (w/w) and was rich in Ser, Gly, Glx and Ala. The isoelectric point was pH 8.2, the pH optimum 4.6-5.2 and the temperature optimum 50 degrees. The activity was inhibited by Cu2+, Ag+, Hg2+, p-chloromercuribenzoate, and D-glucono-1,5-lactone. The K-m and V-max values for p-nitrophenyl (PNP)-beta-glucopyranoside were 0.12 mM and 0.13 mmol (mg protein)(-1) hr-(1), respectively. The enzyme also acted on PNP-beta-cellobioside, lichenan and laminarin, but was not capable of hydrolysing the glucose-containing polymers isolated from cell walls of carrot cell cultures. Copyright (C) 1996 Elsevier Science Ltd