| Type: | Family | Name: | Glycoside hydrolase, family 14A, bacterial |
| 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.Family 14 (, ) encompasses the beta-amylases. Beta-amylases, which are found in plants and bacteria, hydrolyse 1,4-alpha-glycosidic linkages in starch-type polysaccharide substrates, removingsuccessive maltose units from the non-reducing ends of the chains. In potato plants, the enzyme has been found to work optimally at 40 degrees C,becoming unstable above this temperature. On the basis of sequence comparisons, plant and bacterial beta-amylases can be readily distinguishedfrom each other.The 3D structure of a complex of soybean beta-amylase with an inhibitor (alpha-cyclodextrin) has beendetermined to 3.0A resolution by X-ray diffraction []. 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 []. Sequence alignments allow us to relatefeatures of the bacterial beta-amylases to the soybean structure. | Short Name: | Glyco_hydro_14A_bac |
