Implicated in the defense of plants against pathogens. Hydrolysis of (1->3)-beta-D-glucosidic linkages in (1->3)-beta-D-glucans. Not found in healthy tissues, but accumulates to high levels in the extracellular compartment of leaves in response to pathogen infection or treatment with salicylic acid. The N-terminus is blocked. Belongs to the glycosyl hydrolase 17 family.