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Acta Crystallogr D Biol Crystallogr. 2013 Mar;69(Pt 3):442-50. doi: 10.1107/S0907444912049219. Epub 2013 Feb 16.

Structure of a novel α-amylase AmyB from Thermotoga neapolitana that produces maltose from the nonreducing end of polysaccharides.

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1
Department of Manufacturing Pharmacy and Research Institute for Drug Development, Pusan National University, Busan 609-735, Republic of Korea.

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.

KEYWORDS:

AmyB; Thermotoga neapolitana; glycoside hydrolase family 13; α-amylases

PMID:
23519419
DOI:
10.1107/S0907444912049219
[Indexed for MEDLINE]
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