Exo-1,3-beta-glucan glucohydrolase (Exo-I) (Exo-I)

Exo-1,3-beta-glucan glucohydrolase is a plant enzyme found in barley (Hordeum vulgare) that belongs to the glycosyl hydrolase family 3 (GH3) [1]. Its primary biological role is the hydrolysis of (1->3)-beta-D-glucans, which are major components of plant cell walls and fungal cell walls [3]. During barley germination, this enzyme facilitates the mobilization of energy reserves by breaking down cell wall polysaccharides into glucose [2]. Additionally, it serves as a pathogenesis-related (PR) protein, contributing to the plant's defense against fungal infections by degrading the fungal cell wall [1]. While it is not a target for human therapeutic drugs, it is of significant interest in the brewing and malting industries for its role in cell wall degradation [2]. The enzyme's structure and mechanism have been extensively studied to understand carbohydrate-protein interactions and enzymatic catalysis, particularly its interaction with transition-state analogs like isofagomine [2].

Other names

Barley exo-1,3-beta-glucanase1,3-beta-D-glucan glucohydrolaseExo-beta-glucanaseExo-1,3-beta-glucanaseExo-II

The enzyme catalyzes the hydrolysis of terminal non-reducing (1->3)-beta-D-glucosidic linkages in (1->3)-beta-D-glucans, releasing beta-D-glucose via a retaining mechanism involving two glutamic acid residues acting as a nucleophile and an acid/base catalyst [1][2].