title: Structure of a novel α-amylase AmyB from Thermotoga neapolitana that produces maltose from the nonreducing end of polysaccharides.
abstract: An intracellular α-amylase, AmyB, has been cloned from the hyperthermophilic bacterium Thermotoga neapolitana. AmyB belongs to glycoside hydrolase family 13 and liberates maltose from diverse substrates, including starch, amylose, amylopectin and glycogen. The final product of AmyB is similar to that of typical maltogenic amylases, but AmyB cleaves maltose units from the nonreducing end, which is a unique property of this α-amylase. In this study, the crystal structure of AmyB from T. neapolitana has been determined at 2.4 Å resolution, revealing that the monomeric AmyB comprises domains A, B and C like other α-amylases, but with structural variations. In the structure, a wider active site and a putative extra sugar-binding site at the top of the active site were found. Subsequent biochemical results suggest that the extra sugar-binding site is suitable for recognizing the nonreducing end of the substrates, explaining the unique activity of this enzyme. These findings provide a structural basis for the ability of an α-amylase that has the common α-amylase structure to show a diverse substrate specificity.
authors.affiliation: Department of Manufacturing Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Republic of Korea.
authors.forename: So-Young
authors.initials: SY
authors.lastname: Jun
authors.forename: Jin-Sik
authors.initials: JS
authors.lastname: Kim
authors.forename: Kyoung-Hwa
authors.initials: KH
authors.lastname: Choi
authors.forename: Jaeho
authors.initials: J
authors.lastname: Cha
authors.forename: Nam-Chul
authors.initials: NC
authors.lastname: Ha
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D007527:Isoenzymes / Q000737:chemistry / Q000378:metabolism; D008320:Maltose / Q000096:biosynthesis* / Q000737:chemistry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D011485:Protein Binding; D013379:Substrate Specificity; D046949:Thermotoga neapolitana / Q000201:enzymology*; D014312:Trisaccharides / Q000737:chemistry / Q000378:metabolism; D000516:alpha-Amylases / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007527:Isoenzymes; D014312:Trisaccharides; C008317:maltotriose; D008320:Maltose; D000516:alpha-Amylases
keywords: AmyB; Thermotoga neapolitana; glycoside hydrolase family 13; α-amylases