@article {1412,
	title = {Structural features underlying the selective cleavage of a novel exo-type maltose-forming amylase from Pyrococcus sp. ST04.},
	journal = {Acta Crystallogr D Biol Crystallogr},
	volume = {70},
	year = {2014},
	month = {2014 Jun},
	pages = {1659-68},
	abstract = {<p>A novel maltose-forming \&alpha;-amylase (PSMA) was recently found in the hyperthermophilic archaeon Pyrococcus sp. ST04. This enzyme shows \&lt;13\% amino-acid sequence identity to other known \&alpha;-amylases and displays a unique enzymatic property in that it hydrolyzes both \&alpha;-1,4-glucosidic and \&alpha;-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 1.8 \&Aring; 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 (\&beta;/\&alpha;)7-barrel fold and a C-domain (amino acids 342-597) composed of \&alpha;-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 \&beta;-amylases. The structural features of this novel exo-type maltose-forming \&alpha;-amylase provide a molecular basis for its unique enzymatic characteristics and for its potential use in industrial applications and protein engineering.</p>
},
	keywords = {Amylases, Catalytic Domain, Maltose, Models, Molecular, Mutagenesis, Site-Directed, Protein Conformation, Proteolysis, Pyrococcus, Substrate Specificity},
	issn = {1399-0047},
	doi = {10.1107/S1399004714006567},
	author = {Park, Kwang-Hyun and Jung, Jong-Hyun and Park, Sung-Goo and Lee, Myeong-Eun and Holden, James F and Park, Cheon-Seok and Woo, Eui-Jeon}
}
