1kgx

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[[Image:1kgx.jpg|left|200px]]
[[Image:1kgx.jpg|left|200px]]
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{{Structure
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<!--
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|PDB= 1kgx |SIZE=350|CAPTION= <scene name='initialview01'>1kgx</scene>, resolution 2.0&Aring;
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The line below this paragraph, containing "STRUCTURE_1kgx", creates the "Structure Box" on the page.
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|SITE=
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You may change the PDB parameter (which sets the PDB file loaded into the applet)
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|LIGAND= <scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=PCA:PYROGLUTAMIC+ACID'>PCA</scene>
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or the SCENE parameter (which sets the initial scene displayed when the page is loaded),
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|ACTIVITY= <span class='plainlinks'>[http://en.wikipedia.org/wiki/Alpha-amylase Alpha-amylase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.1 3.2.1.1] </span>
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or leave the SCENE parameter empty for the default display.
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|GENE=
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-->
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|DOMAIN=
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{{STRUCTURE_1kgx| PDB=1kgx | SCENE= }}
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|RELATEDENTRY=[[1bs1|1BS1]], [[1kb3|1KB3]], [[1kgu|1KGU]], [[1kgw|1KGW]]
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|RESOURCES=<span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=1kgx FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1kgx OCA], [http://www.ebi.ac.uk/pdbsum/1kgx PDBsum], [http://www.rcsb.org/pdb/explore.do?structureId=1kgx RCSB]</span>
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}}
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'''Three Dimensional Structure Analysis of the R195Q Variant of Human Pancreatic Alpha Amylase'''
'''Three Dimensional Structure Analysis of the R195Q Variant of Human Pancreatic Alpha Amylase'''
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[[Category: Wang, Y.]]
[[Category: Wang, Y.]]
[[Category: Withers, S G.]]
[[Category: Withers, S G.]]
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[[Category: alpha-amylase]]
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[[Category: Alpha-amylase]]
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[[Category: catalysis]]
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[[Category: Catalysis]]
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[[Category: chloride binding]]
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[[Category: Chloride binding]]
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[[Category: enzyme]]
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[[Category: Enzyme]]
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[[Category: human]]
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[[Category: Human]]
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[[Category: mutagenesis]]
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[[Category: Mutagenesis]]
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[[Category: pancreatic]]
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[[Category: Pancreatic]]
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[[Category: pichia pastori]]
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[[Category: Pichia pastori]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 22:43:59 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Mar 30 21:48:26 2008''
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Revision as of 19:43, 2 May 2008

Image:1kgx.jpg

Template:STRUCTURE 1kgx

Three Dimensional Structure Analysis of the R195Q Variant of Human Pancreatic Alpha Amylase


Overview

Human pancreatic alpha-amylase (HPA) is a member of the alpha-amylase family involved in the degradation of starch. Some members of this family, including HPA, require chloride for maximal activity. To determine the mechanism of chloride activation, a series of mutants (R195A, R195Q, N298S, R337A, and R337Q) were made in which residues in the chloride ion binding site were replaced. Mutations in this binding site were found to severely affect the ability of HPA to bind chloride ions with no binding detected for the R195 and R337 mutant enzymes. X-ray crystallographic analysis revealed that these mutations did not result in significant structural changes. However, the introduction of these mutations did alter the kinetic properties of the enzyme. Mutations to residue R195 resulted in a 20-450-fold decrease in the activity of the enzyme toward starch and shifted the pH optimum to a more basic pH. Interestingly, replacement of R337 with a nonbasic amino acid resulted in an alpha-amylase that no longer required chloride for catalysis and has a pH profile similar to that of wild-type HPA. In contrast, a mutation at residue N298 resulted in an enzyme that had much lower binding affinity for chloride but still required chloride for maximal activity. We propose that the chloride is required to increase the pK(a) of the acid/base catalyst, E233, which would otherwise be lower due to the presence of R337, a positively charged residue.

About this Structure

1KGX is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.

Reference

Probing the role of the chloride ion in the mechanism of human pancreatic alpha-amylase., Numao S, Maurus R, Sidhu G, Wang Y, Overall CM, Brayer GD, Withers SG, Biochemistry. 2002 Jan 8;41(1):215-25. PMID:11772019 Page seeded by OCA on Fri May 2 22:43:59 2008

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