Hydrolyzes sinigrin and, with lower efficiency, p-nitrophenyl beta-D-glucoside. a thioglucoside + H2O = a sugar + a thiol. Hydrolysis of terminal, non-reducing beta-D-glucosyl residues with release of beta-D-glucose. A number of isoforms are produced. According to EST sequences. Specifically expressed in roots. It seems that the absence of a catalytic proton donor in plant myrosinases is not impairing the hydrolysis of glucosinolates. Belongs to the glycosyl hydrolase 1 family.