Celobiohydrolases

Celobiohydrolases, often abbreviated as CBHs, are a class of enzymes belonging to the glycoside hydrolase family. They are primarily involved in the breakdown of cellulose, a major structural component of plant cell walls. Specifically, CBHs act as exoglucanases, meaning they cleave cellobiose units from the ends of cellulose chains. Cellobiose is a disaccharide composed of two glucose units linked by a beta-1,4 glycosidic bond.

These enzymes play a crucial role in the biological degradation of cellulose. They work synergistically with other cellulases, such as endoglucanases and beta-glucosidases, to efficiently hydrolyze the complex cellulose polymer into smaller sugars, mainly glucose. This process is essential for nutrient cycling in ecosystems and is also exploited in industrial applications like biofuel production and the manufacturing of textiles and paper.

There are two main types of celobiohydrolases, classified as CBH I and CBH II, which differ in their substrate specificity and mode of action. CBH I enzymes typically act on the reducing end of the cellulose chain, while CBH II enzymes act on the non-reducing end. The complete breakdown of crystalline cellulose often requires the combined action of both types of CBHs, along with endoglucanases, to disrupt the highly ordered structure of the cellulose fibers. Understanding the function and mechanisms of celobiohydrolases is a key area of research in biomass conversion and biotechnology.