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1kbk

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(New page: 200px<br /> <applet load="1kbk" size="450" color="white" frame="true" align="right" spinBox="true" caption="1kbk, resolution 1.9&Aring;" /> '''Mechanistic Analyses...)
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[[Image:1kbk.gif|left|200px]]<br />
 
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<applet load="1kbk" size="450" color="white" frame="true" align="right" spinBox="true"
 
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caption="1kbk, resolution 1.9&Aring;" />
 
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'''Mechanistic Analyses of Catalysis in Human Pancreatic Alpha-Amylase: Detailed Kinetic and Structural Studies of Mutants of Three Conserved Carboxylic Acids'''<br />
 
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==Overview==
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==Mechanistic Analyses of Catalysis in Human Pancreatic Alpha-Amylase: Detailed Kinetic and Structural Studies of Mutants of Three Conserved Carboxylic Acids==
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The roles of three conserved active site carboxylic acids (D197, E233, and, D300) in the catalytic mechanism of human pancreatic alpha-amylase (HPA), were studied by utilizing site-directed mutagenesis in combination with, structural and kinetic analyses of the resultant enzymes. All three, residues were mutated to both alanine and the respective amide, and a, double alanine mutant (E233A/D300A) was also generated. Structural, analyses demonstrated that there were no significant differences in global, fold for the mutant enzymes. Kinetic analyses were performed on the, mutants, utilizing a range of substrates. All results suggested that D197, was the nucleophile, as virtually all activity (&gt;10(5)-fold decrease in, k(cat) values) was lost for the enzymes mutated at this position when, assayed with several substrates. The significantly greater second-order, rate constant of E233 mutants on "activated" substrates (k(cat)/K(m) value, for alpha-maltotriosyl fluoride = 15 s(-)(1) mM(-)(1)) compared with, "unactivated" substrates (k(cat)/K(m) value for maltopentaose = 0.0030, s(-)(1) mM(-)(1)) strongly suggested that E233 is the general acid, catalyst, as did the pH-activity profiles. Transglycosylation was favored, over hydrolysis for the reactions of several of the enzymes mutated at, D300. At the least, this suggests an overall impairment of the catalytic, mechanism where the reaction then proceeds using the better acceptor, (oligosaccharide instead of water). This may also suggest that D300 plays, a crucial role in enzymic interactions with the nucleophilic water during, the hydrolysis of the glycosidic bond.
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<StructureSection load='1kbk' size='340' side='right'caption='[[1kbk]], [[Resolution|resolution]] 1.90&Aring;' scene=''>
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== Structural highlights ==
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<table><tr><td colspan='2'>[[1kbk]] is a 1 chain structure with sequence from [https://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1KBK OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1KBK FirstGlance]. <br>
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</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.9&#8491;</td></tr>
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<tr id='ligand'><td class="sblockLbl"><b>[[Ligand|Ligands:]]</b></td><td class="sblockDat" id="ligandDat"><scene name='pdbligand=CA:CALCIUM+ION'>CA</scene>, <scene name='pdbligand=CL:CHLORIDE+ION'>CL</scene>, <scene name='pdbligand=NAG:N-ACETYL-D-GLUCOSAMINE'>NAG</scene>, <scene name='pdbligand=PCA:PYROGLUTAMIC+ACID'>PCA</scene></td></tr>
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<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1kbk FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1kbk OCA], [https://pdbe.org/1kbk PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1kbk RCSB], [https://www.ebi.ac.uk/pdbsum/1kbk PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1kbk ProSAT]</span></td></tr>
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</table>
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== Function ==
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[https://www.uniprot.org/uniprot/AMYP_HUMAN AMYP_HUMAN]
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== Evolutionary Conservation ==
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[[Image:Consurf_key_small.gif|200px|right]]
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Check<jmol>
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<jmolCheckbox>
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<scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/kb/1kbk_consurf.spt"</scriptWhenChecked>
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<scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview01.spt</scriptWhenUnchecked>
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<text>to colour the structure by Evolutionary Conservation</text>
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</jmolCheckbox>
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</jmol>, as determined by [http://consurfdb.tau.ac.il/ ConSurfDB]. You may read the [[Conservation%2C_Evolutionary|explanation]] of the method and the full data available from [http://bental.tau.ac.il/new_ConSurfDB/main_output.php?pdb_ID=1kbk ConSurf].
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<div style="clear:both"></div>
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==About this Structure==
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==See Also==
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1KBK is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with NAG, CA and CL as [http://en.wikipedia.org/wiki/ligands ligands]. Active as [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] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1KBK OCA].
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*[[Amylase 3D structures|Amylase 3D structures]]
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__TOC__
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==Reference==
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</StructureSection>
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Mechanistic analyses of catalysis in human pancreatic alpha-amylase: detailed kinetic and structural studies of mutants of three conserved carboxylic acids., Rydberg EH, Li C, Maurus R, Overall CM, Brayer GD, Withers SG, Biochemistry. 2002 Apr 2;41(13):4492-502. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=11914097 11914097]
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[[Category: Alpha-amylase]]
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[[Category: Homo sapiens]]
[[Category: Homo sapiens]]
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[[Category: Single protein]]
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[[Category: Large Structures]]
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[[Category: Brayer, G.D.]]
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[[Category: Brayer GD]]
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[[Category: Li, C.]]
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[[Category: Li C]]
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[[Category: Maurus, R.]]
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[[Category: Maurus R]]
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[[Category: Overall, C.M.]]
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[[Category: Overall CM]]
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[[Category: Rydberg, E.H.]]
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[[Category: Rydberg EH]]
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[[Category: Withers, S.G.]]
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[[Category: Withers SG]]
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[[Category: CA]]
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[[Category: CL]]
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[[Category: NAG]]
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[[Category: amylase]]
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[[Category: carbohydrate metabolism]]
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[[Category: catalysis]]
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[[Category: diabetes]]
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[[Category: enzyme]]
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[[Category: glycosidase]]
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[[Category: glycosylation]]
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[[Category: human]]
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[[Category: hydrolase]]
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[[Category: mutagenesis]]
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[[Category: pancreatic]]
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''Page seeded by [http://ispc.weizmann.ac.il/oca OCA ] on Mon Nov 12 17:49:42 2007''
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Current revision

Mechanistic Analyses of Catalysis in Human Pancreatic Alpha-Amylase: Detailed Kinetic and Structural Studies of Mutants of Three Conserved Carboxylic Acids

PDB ID 1kbk

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