Beta-amylase (alpha-1,4-glucan maltohydrolase; EC 3.2.1.2) catalyses the release of beta-anomeric maltose from the non-reducing ends of starch. It is known to function by multiple attack, several maltose molecules being produced before the maltooligosaccharide chain is released from the active site. Although known to bind a calcium ion, the metal is not involved in catalysis.
On the basis of its sequence alignment, beta-amylase has been classified as belonging to the glycoside hydrolase family 14 (GH14). It is an inverting glycoside hydrolase that is distributed throughout higher plants, oomycetes and bacteria. However, on the basis of sequence comparisons, plant and bacterial beta-amylases can be readily distinguished from each other.
Defined by 5 residues: ASP:A-101GLU:A-186THR:A-342GLU:A-380LEU:A-383