| Type: | Conserved_site | Name: | Glycoside hydrolase, family 14, conserved site |
| Description: | O-Glycosyl hydrolases () 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 glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families [, ]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.Glycoside hydrolase family 14 comprises enzymes with only one known activity; beta-amylase (). A Glu residue has been proposed as a catalytic residue, but it is not known if it is the nucleophile or the proton donor. Beta-amylase [, ] is an enzyme that hydrolyses 1,4-alpha-glucosidic linkages in starch-type polysaccharide substrates so as to removesuccessive maltose units from the non-reducing ends of the chains. Beta-amylase is present in certain bacteria as well as in plants.The 3D structure of a complex of soybean beta-amylase with an inhibitor (alpha-cyclodextrin) has been determined to 3.0A resolution by X-raydiffraction []. The enzyme folds into large and small domains: the largedomain has a (beta alpha)8 super-secondary structural core, while the smaller is formed from two long loops extending from the beta-3 and beta-4 strandsof the (beta alpha)8 fold []. The interface of the two domains, togetherwith shorter loops from the (beta alpha)8 core, form a deep cleft, in which the inhibitor binds []. Two maltose molecules also bind in the cleft,one sharing a binding site with alpha-cyclodextrin, and the other sitting more deeply in the cleft [].This entry represents two highly conserved sequence regions found in all known beta-amylases. The first of these regions (BETA_AMYLASE_1) is located in the N-terminal section of the enzymes and contains an aspartate which is known [] to be involved in the catalytic mechanism. The second (BETA_AMYLASE_2), located in a more central location, is centred around a glutamate which is also involved [] in the catalytic mechanism. | Short Name: | Glyco_hydro_14_CS |
