carbohydrateactive

Carbohydrate-active enzymes, commonly referred to as CAZymes, are enzymes that synthesize, modify, or degrade complex carbohydrates such as polysaccharides and glycosides. They are produced by organisms across all domains of life and play central roles in metabolism, digestion, and ecological carbon cycling. CAZymes are important in biotechnology, biofuel production, food processing, and medicine, where their ability to manipulate carbohydrate structures is exploited.

Classification and scope: In the CAZy framework, carbohydrate-active enzymes are grouped into families based on amino acid sequence similarities and catalytic mechanisms. The main classes are glycoside hydrolases (GHs), which hydrolyze glycosidic bonds; glycosyltransferases (GTs), which form glycosidic bonds; polysaccharide lyases (PLs), which cleave polysaccharides via eliminative mechanisms; carbohydrate esterases (CEs), which remove ester groups from sugars; auxiliary activities (AAs), which include oxidative or redox enzymes acting on carbohydrates or lignocellulose; and carbohydrate-binding modules (CBMs), non-catalytic domains that bind carbohydrates and enhance enzyme efficiency. The CAZy database curates these families, providing annotations, sequences, and distribution across organisms.

Structures and function: Many CAZymes are multi-domain proteins combining catalytic modules with CBMs to improve substrate binding and turnover. Enzyme activity is often specific for particular linkages, monosaccharide compositions, and branching patterns, reflecting the diversity of carbohydrate structures found in nature.

Applications and impact: CAZymes are central to biomass conversion, enabling the breakdown of cellulose, hemicellulose, and other polysaccharides for biofuels and bioproducts. They also find use in food and feed processing, textile and paper industries, and pharmaceutical research, where engineered CAZyme systems offer sustainable approaches to modify or synthesize carbohydrate-containing materials.