Glycoside hydrolase, family 15 <p>O-Glycosyl hydrolases <db_xref db="EC" dbkey="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 [<cite idref="PUB00004870"/>, <cite idref="PUB00005266"/>]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site.</p><p>Glycoside hydrolase family 15 <db_xref db="CAZY" dbkey="GH15"/> comprises enzymes with several known activities; glucoamylase (<db_xref db="EC" dbkey="3.2.1.3"/>); alpha-glucosidase (<db_xref db="EC" dbkey="3.2.1.20"/>); glucodextranase (<db_xref db="EC" dbkey="3.2.1.70"/>). </p><p>Glucoamylase (GA) catalyses the release ofD-glucose from the non-reducing ends of starch and other oligo- or poly-saccharides. Studies of fungal GA have indicated 3 closely-clustered acidicresidues that play a role in the catalytic mechanism [<cite idref="PUB00004952"/>]. This region is also conserved in a recently sequenced bacterial GA [<cite idref="PUB00001422"/>].</p><p>The 3D structure of the pseudo-tetrasaccharide acarbose complexed withglucoamylase II(471) from <taxon tax_id="105351">Aspergillus awamori</taxon> var. X100 has been determinedto 2.4A resolution [<cite idref="PUB00002848"/>]. The protein belongs to the mainly-alpha class, and contains 19 helices and 9 strands.</p>