Beta-glucosidase acting as a preformed defense system. Hydrolyzes the bisdesmosides avenacosides A and B to 26-desgluco-avenacosides exhibiting fungicidal activity. Can use beta-fucoside > beta-glucoside > beta-galactoside > beta-xyloside as substrates, but not alpha-glycosides, beta-thioglucosides and disaccharides. avenacoside B + H2O = 26-desgluco-avenacoside B + D-glucose Inhibited by N-(3-Dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC). The activity increases with rising aggregation of the enzyme. kcat is 982000 sec(-1) with avenacosides as substrate. kcat is 3090 sec(-1) with p-nitrophenyl-beta-D-glucopyranoside as substrate. kcat is 290 sec(-1) with genistin as substrate. Optimum pH is 6.0. Homo- and heteromultimer with P60B in a 1:1 stoichiometry. Aggregates to form the fibrillar stromacentre. Found in a fibrillar spherulite called stromacentre. Expressed in caryopses, coleoptiles, primary leaves, and etiolated and green seedlings, but not in roots. Long fibrillar homomultimers are formed by linear stacking of trimeric units. The multimerization of the enzyme promotes formation of a long central channel with narrow openings at the sides. The active sites are localized inside the tunnels, constraining the accessibility of substrates and products. Belongs to the glycosyl hydrolase 1 family.