Structural features underlying the selective cleavage of a novel exo-type maltose-forming amylase from Pyrococcus sp. ST04

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Title
Structural features underlying the selective cleavage of a novel exo-type maltose-forming amylase from Pyrococcus sp. ST04
Author(s)
K H Park; J H Jung; Sung Goo Park; M E Lee; J F Holden; C S Park; Eui-jeon Woo
Bibliographic Citation
Acta Crystallographica Section D-Biological Crystallography, vol. 70, no. 6, pp. 1659-1668
Publication Year
2014
Abstract
A novel maltose-forming α-amylase (PSMA) was recently found in the hyperthermophilic archaeon Pyrococcus sp. ST04. This enzyme shows <13% amino-acid sequence identity to other known α-amylases and displays a unique enzymatic property in that it hydrolyzes both α-1,4-glucosidic and α-1,6-glucosidic linkages of substrates, recognizing only maltose units, in an exo-type manner. Here, the crystal structure of PSMA at a resolution of 1.8A is reported, showing a tight ring-shaped tetramer with monomers composed of two domains: an N-domain (amino acids 1-341) with a typical GH57 family (β/α)7-barrel fold and a C-domain (amino acids 342-597) composed of α-helical bundles. A small closed cavity observed in proximity to the catalytic residues Glu153 and Asp253 at the domain interface has the appropriate volume and geometry to bind a maltose unit, accounting for the selective exo-type maltose hydrolysis of the enzyme. A narrow gate at the putative subsite +1 formed by residue Phe218 and Phe452 is essential for specific cleavage of glucosidic bonds. The closed cavity at the active site is connected to a short substrate-binding channel that extends to the central hole of the tetramer, exhibiting a geometry that is significantly different from classical maltogenic amylases or β-amylases. The structural features of this novel exo-type maltose-forming α-amylase provide a molecular basis for its unique enzymatic characteristics and for its potential use in industrial applications and protein engineering.
Keyword
exo-type hydrolaseglycoside hydrolase family 57maltose-forming α-amylasePyrococcus sp. ST04
ISSN
0907-4449
Publisher
Int Union Crystallography
DOI
http://dx.doi.org/10.1107/S1399004714006567
Type
Article
Appears in Collections:
Division of Biomedical Research > Disease Target Structure Research Center > 1. Journal Articles
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