Endoglucanase

Endoglucanase is an enzyme that catalyzes the random hydrolysis of internal β‑1,4‑glycosidic bonds in cellulose, producing soluble cello-oligosaccharides and contributing to the overall depolymerization of cellulose fibers. It is a member of the glycoside hydrolase (GH) family 5, 9, and 7, among others, and is defined by a catalytic domain that typically contains a double‐psi β barrel or a TIM barrel fold. The catalytic mechanism involves a two‐step retaining or inverting reaction depending on the GH family, employing a pair of acidic residues (often aspartate and glutamate) that act as proton donor and nucleophile.

Endoglucanases are produced by a wide variety of organisms including bacteria, fungi, and plant pathogens. In microbial cellulose utilization, the enzyme works synergistically with cellobiohydrolases and β‑glucosidases, forming a cellulase complex that efficiently deconstructs crystalline cellulose. The enzymes also play roles in plant cell wall remodeling during growth and defense, as well as in fungal invasion of plant tissues.

Industrial applications of endoglucanases are extensive in the pulp and paper, textile, animal feed, and biofuel industries. In biofuel production, endoglucanases are combined with exoglucanases and β‑glucosidases to convert cellulosic biomass into fermentable sugars for ethanol production. In animal feed, they improve digestibility of cellulose-rich forage. Additionally, endoglucanases are employed as aiding agents in detergent formulations and in the modification of plant-derived materials.

Research efforts focus on improving catalytic efficiency, thermal stability, and enzyme synergy. Genetic engineering of microbial strains and protein engineering of catalytic domains aim to produce industrially relevant enzymes with higher activity and broader pH optima. The study of endoglucanase structure-function relationships has also provided insights into the evolution of glycoside hydrolases and the mechanisms by which enzymes degrade complex polysaccharides.