Publication Abstract from PubMed
A truncated form of an alpha-amylase, GTA, from thermophilic Geobacillus thermoleovorans CCB_US3_UF5 was biochemically and structurally characterized. The recombinant GTA, which lacked both the N- and C-terminal transmembrane regions, functioned optimally at 70 degrees C and pH 6.0. While enzyme activity was not enhanced by the addition of CaCl2, GTA's thermostability was significantly improved in the presence of CaCl2. The structure, in complex with an acarbose-derived pseudo-hexasaccharide, consists of the typical three domains and binds one Ca(2+) ion. This Ca(2+) ion was strongly bound and not chelated by EDTA. A predicted second Ca(2+)-binding site, however, was disordered. With limited subsites, two novel substrate-binding residues, Y147 and Y182, may help increase substrate affinity. No distinct starch-binding domain is present, although two regions rich in aromatic residues have been observed. GTA, with a smaller domain B and several shorter loops compared to other alpha-amylases, has one of the most compact alpha-amylase folds that may contribute greatly to its tight Ca(2+) binding and thermostability.
Crystal structure of a compact alpha-amylase from Geobacillus thermoleovorans.,Mok SC, Teh AH, Saito JA, Najimudin N, Alam M Enzyme Microb Technol. 2013 Jun 10;53(1):46-54. doi:, 10.1016/j.enzmictec.2013.03.009. Epub 2013 Mar 28. PMID:23683704[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
