Degradation of glucosinolates (glucose residue linked by a thioglucoside bound to an amino acid derivative) to glucose, sulfate and any of the products: thiocyanates, isothiocyanates, nitriles, epithionitriles or oxazolidine-2-thiones. These toxic degradation products can deter insect herbivores. Seems to function in abscisic acid (ABA) and methyl jasmonate (MeJA) signaling in guard cells. Functionally redundant with TGG2. 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. Homodimer. Expressed in guard cells, phloem-associated cells and myrosin cells. 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.