Family

Glycoside hydrolase, family 14 (IPR001554)

Short name: Glyco_hydro_14

Family relationships

Description

O-Glycosyl hydrolases (EC:3.2.1.) 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 glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families [PMID: 7624375, PMID: 8535779]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.

Glycoside hydrolase family 14 GH14 comprises enzymes with only one known activity; beta-amylase (EC:3.2.1.2). 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 [PMID: 2457058, PMID: 2464171] is an enzyme that hydrolyses 1,4-alpha-glucosidic linkages in starch-type polysaccharide substrates so as to remove successive maltose units from the non-reducing ends of the chains. Beta-amylase is present in certain bacteria as well as in plants.

Three highly conserved sequence regions are found in all known beta-amylases. The first of these regions is located in the N-terminal section of the enzymes and contains an aspartate which is known [PMID: 2474529] to be involved in the catalytic mechanism. The second, located in a more central location, is centred around a glutamate which is also involved [PMID: 8174545] in the catalytic mechanism.

The 3D structure of a complex of soybean beta-amylase with an inhibitor (alpha-cyclodextrin) has been determined to 3.0A resolution by X-ray diffraction [PMID: 1491009]. The enzyme folds into large and small domains: the large domain 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 strands of the (beta alpha)8 fold [PMID: 1491009]. The interface of the two domains, together with shorter loops from the (beta alpha)8 core, form a deep cleft, in which the inhibitor binds [PMID: 1491009]. 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 [PMID: 1491009].

GO terms

Biological Process

GO:0000272 polysaccharide catabolic process

Molecular Function

GO:0016161 beta-amylase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
Pfam
PRINTS