Beta-glucosidase highly specific for the cleavage of C-26-bound glucose moiety of furostanol glycosides torvosides A and H. Hydrolyzes only p-nitrophenyl-beta-glucoside, but not p-nitrophenyl-beta-D-fucoside, p-nitrophenyl-beta-L-fucoside, p-nitrophenyl-beta-D-xyloside, p-nitrophenyl-beta-D-galactoside, p-nitrophenyl-beta-D-NAc-glucosamine, p-nitrophenyl-beta-D-mannoside or any of the p-nitrophenyl-alpha-glycosides tested. H2O + protodioscin = 26-deglucoprotodioscin + D-glucose Inhibited by Hg(2+) and D-glucono-1,5-lactone. kcat is 8.6 sec(-1) for torvoside A. kcat is 7.7 sec(-1) for torvoside B. kcat is 9.1 sec(-1) for p-nitrophenyl-beta-glucoside. kcat is 8.3 sec(-1) for 4-methylumbelliferyl-beta-glucoside. Optimum pH is 5.0. Monomer. Expressed in petioles and leaves, but not in fruits. Glycosylated. Belongs to the glycosyl hydrolase 3 family.