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'''THE ACTIVE CENTER OF A MAMMALIAN ALPHA-AMYLASE. THE STRUCTURE OF THE COMPLEX OF A PANCREATIC ALPHA-AMYLASE WITH A CARBOHYDRATE INHIBITOR REFINED TO 2.2 ANGSTROMS RESOLUTION''' | '''THE ACTIVE CENTER OF A MAMMALIAN ALPHA-AMYLASE. THE STRUCTURE OF THE COMPLEX OF A PANCREATIC ALPHA-AMYLASE WITH A CARBOHYDRATE INHIBITOR REFINED TO 2.2 ANGSTROMS RESOLUTION''' | ||
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==About this Structure== | ==About this Structure== | ||
1PPI is a [[Single protein]] structure | 1PPI is a [[Single protein]] structure. The following page contains interesting information on the relation of 1PPI with [[http://pdb.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb74_1.html Alpha-amylase]]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1PPI OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Payan, F.]] | [[Category: Payan, F.]] | ||
[[Category: Qian, M.]] | [[Category: Qian, M.]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 05:20:26 2008'' | |||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | |||
Revision as of 05:20, 3 May 2008
THE ACTIVE CENTER OF A MAMMALIAN ALPHA-AMYLASE. THE STRUCTURE OF THE COMPLEX OF A PANCREATIC ALPHA-AMYLASE WITH A CARBOHYDRATE INHIBITOR REFINED TO 2.2 ANGSTROMS RESOLUTION
OverviewOverview
An X-ray structure analysis of a crystal of pig pancreatic alpha-amylase (EC 3.2.1.1) that was soaked with acarbose (a pseudotetrasaccharide alpha-amylase inhibitor) showed electron density corresponding to five fully occupied subsites in the active site. The crystal structure was refined to an R-factor of 15.3%, with a root mean square deviation in bond distances of 0.015 A. The model includes all 496 residues of the enzyme, one calcium ion, one chloride ion, 393 water molecules, and five bound sugar rings. The pseudodisaccharide acarviosine that is the essential structural unit responsible for the activity of all inhibitors of the acarbose type was located at the catalytic center. The carboxylic oxygens of the catalytically competent residues Glu233 and Asp300 form hydrogen bonds with the "glycosidic" NH group of the acarviosine group. The third residue of the catalytic triad Asp197 is located on the opposite side of the inhibitor binding cleft with one of its carbonyl oxygens at a 3.3-A distance from the anomeric carbon C-1 of the inhibitor center. Binding of inhibitor induces structural changes at the active site of the enzyme. A loop region between residues 304 and 309 moves in toward the bound saccharide, the resulting maximal mainchain movement being 5 A for His305. The side chain of residue Asp300 rotates upon inhibitor binding and makes strong van der Waals contacts with the imidazole ring of His299. Four histidine residues (His101, His201, His299, and His305) are found to be hydrogen-bonded with the inhibitor. Many protein-inhibitor hydrogen bond interactions are observed in the complex structure, as is clear hydrophobic stacking of aromatic residues with the inhibitor surface. The chloride activator ion and structural calcium ion are hydrogen-bonded via their ligands and water molecules to the catalytic residues.
About this StructureAbout this Structure
1PPI is a Single protein structure. The following page contains interesting information on the relation of 1PPI with [Alpha-amylase]. Full crystallographic information is available from OCA.
ReferenceReference
The active center of a mammalian alpha-amylase. Structure of the complex of a pancreatic alpha-amylase with a carbohydrate inhibitor refined to 2.2-A resolution., Qian M, Haser R, Buisson G, Duee E, Payan F, Biochemistry. 1994 May 24;33(20):6284-94. PMID:8193143 Page seeded by OCA on Sat May 3 05:20:26 2008