Enzymes containing this domain, such as alpha-amylase, belong to family 13 of the glycosyl hydrolases. The maltogenic alpha-amylase is an enzyme that catalyses the hydrolysis of (1-4)-alpha-D-glucosidic linkages in polysaccharides so as to remove successive alpha-maltose residues from the non-reducing ends of the chains in the conversion of starch to maltose. Other enzymes include neopullulanase … expand

Enzymes containing this domain, such as alpha-amylase, belong to family 13 of the glycosyl hydrolases. The maltogenic alpha-amylase is an enzyme that catalyses the hydrolysis of (1-4)-alpha-D-glucosidic linkages in polysaccharides so as to remove successive alpha-maltose residues from the non-reducing ends of the chains in the conversion of starch to maltose. Other enzymes include neopullulanase, which hydrolyses pullulan to panose, and cyclomaltodextrinase, which hydrolyses cyclodextrins.

This entry represents the catalytic domain found in several protein members of this family. It has a structure consisting of an 8-stranded α/β barrel that contains the active site, interrupted by a ~70 amino acid calcium-binding domain protruding between β-strand 3 and α-helix 3, and a carboxyl-terminal β-barrel domain [ PUBMED:16302977 ].

Family GH13 is the major glycoside hydrolase family acting on substrates containing α-glucoside linkages. GH13 contains hydrolases, transglycosidases, and isomerases [ PUBMED:17724034 ]; noticeably, animal amino acid transporters [ PUBMED:9302327 ], which have no glycosidase activity [ PUBMED:19878315 ], are also GH13 members. The enzymes are found in a very wide range of organisms from all kingdoms. The GH13 enzymes have a wide range of different preferred substrates and products. For example, the α-amylases prefer polysaccharides of the α-1,4-glucan type, such as amylose and amylopectin, but are also able to attack the supramolecular structures represented by starch granules and glycogen particles. Among thousands of sequences and ~30 different enzyme specificities [ PUBMED:17085431 ] many are closely related to each other; GH13 therefore has officially been subdivided into almost 40 subfamilies [ PUBMED:18838391 ]. In general, the GH13 members are multidomain proteins with catalytic (β/α)8-barrel (i.e. TIM-barrel) domain (called domain A) having a small domain B (usually varying in length and of irregular structure) [ PUBMED:17724034 ]. Some of these enzymes include:

• α-amylase EC:3.2.1.1
• oligo-1,6-glucosidase EC:3.2.1.10
• α-glucosidase EC:3.2.1.20
• pullulanase EC:3.2.1.4
• cyclomaltodextrinase EC:3.2.1.54
• maltotetraose-forming α-amylase EC:3.2.1.60
• isoamylase EC:3.2.1.68
• dextran glucosidase EC:3.2.1.70
• trehalose-6-phosphate hydrolase EC:3.2.1.93
• maltohexaose-forming α-amylase EC:3.2.1.9 )
• maltotriose-forming α-amylase EC:3.2.1.116
• maltogenic amylase EC:3.2.1.133
• neopullulanase EC:3.2.1.135
• malto-oligosyltrehalose trehalohydrolase EC:3.2.1.141
• limit dextrinase EC:3.2.1.142
• amylosucrase EC:2.4.1.4
• sucrose phosphorylase EC:2.4.1.7
• cyclomaltodextrin glucanotransferase (CGTase) EC:2.4.1.19
• 4-α-glucanotransferase EC:2.4.1.25
• isomaltulose synthase EC:5.4.99.11
• trehalose synthase EC:5.4.99.16

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 [ PUBMED:7624375 PUBMED:8535779 ]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) website.