Glycoside hydrolasesEC3.2.1. are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycoside hydrolases, based on sequence similarity, has led to the definition of >100 different families.[1][2][3] This classification is available on the CAZy web site,[4][5] and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.[6][7] y[ _]9
Glucoamylase (GA) catalyses the release of D-glucose from the non-reducing ends of starch and other oligo- or poly-saccharides. Studies of fungal GA have indicated 3 closely clustered acidic residues that play a role in the catalytic mechanism.[8] This region is also conserved in a recently sequenced bacterial GA.[9]
The 3D structure of the pseudo-tetrasaccharideacarbose complexed with glucoamylase II(471) from Aspergillus awamori var. X100 has been determined to 2.4A resolution.[10] The protein belongs to the mainly alpha class, and contains 19 helices and 9 strands.
^Sierks MR, Ford C, Reilly PJ, Svensson B (January 1990). "Catalytic mechanism of fungal glucoamylase as defined by mutagenesis of Asp176, Glu179 and Glu180 in the enzyme from Aspergillus awamori". Protein Engineering. 3 (3): 193–8. doi:10.1093/protein/3.3.193. PMID1970434.
^Ohnishi H, Kitamura H, Minowa T, Sakai H, Ohta T (July 1992). "Molecular cloning of a glucoamylase gene from a thermophilic Clostridium and kinetics of the cloned enzyme". European Journal of Biochemistry. 207 (2): 413–8. doi:10.1111/j.1432-1033.1992.tb17064.x. PMID1633799.