1,4-beta-glucan cellobiohydrolase II (CBHII)

1,4-beta-glucan cellobiohydrolase II (CBHII) is a glycosyl hydrolase, typically belonging to the GH6 family, that plays a vital role in the breakdown of cellulose into fermentable sugars. Primarily secreted by cellulolytic fungi such as Trichoderma reesei and various bacteria, the enzyme acts as an exo-glucanase, processively cleaving cellobiose units from the non-reducing ends of crystalline cellulose strands (1, 2). Structurally, CBHII is characterized by a tunnel-shaped active site that allows it to thread single cellulose chains for sequential hydrolysis, often working in synergy with cellobiohydrolase I and endoglucanases (3). While not a traditional therapeutic target for human disease, CBHII is of significant industrial importance in the production of second-generation biofuels and the textile industry (4). In a medical context, cellulase mixtures containing CBHII are occasionally used as a treatment for phytobezoars (gastric masses composed of plant fiber), though the enzyme itself is more commonly recognized as a potent occupational allergen capable of inducing asthma or hypersensitivity in sensitized individuals (5, 6). Sources: 1. UniProt KB (P07987) - Exoglucanase 2 (Cel6A). 2. Enzyme Nomenclature (EC 3.2.1.91) - Cellulose 1,4-beta-cellobiosidase (non-reducing end). 3. CAZy Database - Glycoside Hydrolase Family 6. 4. PubMed (PMID: 21477103) - Structure and function of cellobiohydrolases. 5. PubMed (PMID: 2470535) - Treatment of gastric phytobezoars with cellulase. 6. PubMed (PMID: 8011210) - Occupational asthma caused by cellulase.

Other names

Exo-cellobiohydrolase 2Cellobiohydrolase II1,4-beta-D-glucan cellobiosidaseCellulase 1,4-beta-cellobiosidase IIGH6 family cellulaseCel6A

The enzyme catalyzes the hydrolysis of (1->4)-beta-D-glucosidic linkages in cellulose, processively releasing cellobiose units from the non-reducing ends of the polymer chain using an inverting catalytic mechanism.