GH16

GH16 is a glycoside hydrolase family cataloged in the CAZy database. Members of GH16 catalyze hydrolysis or transglycosylation of glycosidic bonds in beta-glucans, with substrates including xyloglucan and related polysaccharides. The best characterized members are the xyloglucan endotransglucosylase/hydrolases (XTH) found in plants, which can cleave xyloglucan chains and, in some cases, re-attach them to other polysaccharide chains, thereby remodeling the plant cell wall during growth and development. Other GH16 enzymes are found in fungi and bacteria and contribute to degradation of beta-glucans such as laminarin or glucans in microbial cell walls.

The family is defined by conserved sequence motifs and a shared catalytic mechanism that uses carboxylate residues to cleave glycosidic bonds; individual enzymes display varying activities, including predominantly hydrolysis or transglycosylation. GH16 enzymes exhibit diversity in substrate preference and localization, spanning secreted extracellular enzymes to intracellular variants.

Distribution and function: GH16 enzymes occur across plants, fungi, bacteria, and other organisms. In plants, XTH enzymes participate in cell wall remodeling crucial for cell expansion, development, and response to environmental cues. In microorganisms, GH16 members contribute to the breakdown and utilization of polysaccharides in the environment or in host-associated niches.

Applications and significance: Because of their roles in plant cell wall modification and microbial polysaccharide degradation, GH16 enzymes are studied for insights into plant growth and defense, as well as potential applications in biomass conversion and industrial processing of plant-derived polysaccharides. Research continues to characterize substrate specificities, regulation, and structure–function relationships within the family.