GH13

GH13 refers to glycoside hydrolase family 13, a major enzyme family catalogued by the CAZy database. Members catalyze hydrolysis of alpha-glycosidic bonds in starch and related polysaccharides, and include enzymes such as alpha-amylases, maltogenic amylases, amylopullulanases, cyclodextrin glycosyltransferases, and some alpha-glucosidases and related transferases. They act on substrates like starch, dextrins, pullulan, and cyclodextrins.

Most GH13 enzymes share a core TIM-barrel catalytic domain, sometimes with additional N- or C-terminal domains and carbohydrate-binding modules. The active site typically features a catalytic acid/base residue pair that mediates a retaining two-step mechanism, with a transient glycosyl-enzyme intermediate.

GH13 is highly diverse, organized into subfamilies in CAZy to reflect sequence similarity and substrate preferences. Substrate specificities range from endo-acting hydrolysis of alpha-1,4 and alpha-1,6 linkages to exo-acting glucosidase activity. Enzymes may be optimized for temperature and pH, and modular appendages influence substrate binding and stability under industrial conditions.

Industrial relevance includes starch processing, baking, brewing, and the production of cyclodextrins, as well as applications in biofuel production and carbohydrate modification. The broad substrate range and adaptable structures make GH13 enzymes a focal point in both basic enzymology and applied biotechnology.