View source for 1jxj


==Role of mobile loop in the mechanism of human salivary amylase==
<StructureSection load='1jxj' size='340' side='right'caption='[[1jxj]], [[Resolution|resolution]] 1.99&Aring;' scene=''>
== Structural highlights ==
<table><tr><td colspan='2'>[[1jxj]] 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=1JXJ OCA]. For a <b>guided tour on the structure components</b> use [https://proteopedia.org/fgij/fg.htm?mol=1JXJ FirstGlance]. <br>
</td></tr><tr id='method'><td class="sblockLbl"><b>[[Empirical_models|Method:]]</b></td><td class="sblockDat" id="methodDat">X-ray diffraction, [[Resolution|Resolution]] 1.99&#8491;</td></tr>
<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=PCA:PYROGLUTAMIC+ACID'>PCA</scene></td></tr>
<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[https://proteopedia.org/fgij/fg.htm?mol=1jxj FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=1jxj OCA], [https://pdbe.org/1jxj PDBe], [https://www.rcsb.org/pdb/explore.do?structureId=1jxj RCSB], [https://www.ebi.ac.uk/pdbsum/1jxj PDBsum], [https://prosat.h-its.org/prosat/prosatexe?pdbcode=1jxj ProSAT]</span></td></tr>
</table>
== Function ==
[https://www.uniprot.org/uniprot/AMY1A_HUMAN AMY1A_HUMAN] Calcium-binding enzyme that initiates starch digestion in the oral cavity (PubMed:12527308). Catalyzes the hydrolysis of internal (1->4)-alpha-D-glucosidic bonds, yielding a mixture of maltose, isomaltose, small amounts of glucose as well as small linear and branched oligosaccharides called dextrins (PubMed:12527308).<ref>PMID:12527308</ref> 
== Evolutionary Conservation ==
[[Image:Consurf_key_small.gif|200px|right]]
Check<jmol>
  <jmolCheckbox>
    <scriptWhenChecked>; select protein; define ~consurf_to_do selected; consurf_initial_scene = true; script "/wiki/ConSurf/jx/1jxj_consurf.spt"</scriptWhenChecked>
    <scriptWhenUnchecked>script /wiki/extensions/Proteopedia/spt/initialview03.spt</scriptWhenUnchecked>
    <text>to colour the structure by Evolutionary Conservation</text>
  </jmolCheckbox>
</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=1jxj ConSurf].
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<div style="background-color:#fffaf0;">
== Publication Abstract from PubMed ==
The nonreducing end of the substrate-binding site of human salivary alpha-amylase contains two residues Trp58 and Trp59, which belong to beta2-alpha2 loop of the catalytic (beta/alpha)(8) barrel. While Trp59 stacks onto the substrate, the exact role of Trp58 is unknown. To investigate its role in enzyme activity the residue Trp58 was mutated to Ala, Leu or Tyr. Kinetic analysis of the wild-type and mutant enzymes was carried out with starch and oligosaccharides as substrates. All three mutants exhibited a reduction in specific activity (150-180-fold lower than the wild type) with starch as substrate. With oligosaccharides as substrates, a reduction in k(cat), an increase in K(m) and distinct differences in the cleavage pattern were observed for the mutants W58A and W58L compared with the wild type. Glucose was the smallest product generated by these two mutants in the hydrolysis oligosaccharides; in contrast, wild-type enzyme generated maltose as the smallest product. The production of glucose by W58L was confirmed from both reducing and nonreducing ends of CNP-labeled oligosaccharide substrates. The mutant W58L exhibited lower binding affinity at subsites -2, -3 and +2 and showed an increase in transglycosylation activity compared with the wild type. The lowered affinity at subsites -2 and -3 due to the mutation was also inferred from the electron density at these subsites in the structure of W58A in complex with acarbose-derived pseudooligosaccharide. Collectively, these results suggest that the residue Trp58 plays a critical role in substrate binding and hydrolytic activity of human salivary alpha-amylase.

Human salivary alpha-amylase Trp58 situated at subsite -2 is critical for enzyme activity.,Ramasubbu N, Ragunath C, Mishra PJ, Thomas LM, Gyemant G, Kandra L Eur J Biochem. 2004 Jun;271(12):2517-29. PMID:15182367<ref>PMID:15182367</ref>

From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
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<div class="pdbe-citations 1jxj" style="background-color:#fffaf0;"></div>

==See Also==
*[[Amylase 3D structures|Amylase 3D structures]]
== References ==
<references/>
__TOC__
</StructureSection>
[[Category: Homo sapiens]]
[[Category: Large Structures]]
[[Category: Mishra PJ]]
[[Category: Ragunath C]]
[[Category: Ramasubbu N]]
[[Category: Thomas LM]]
[[Category: Wang Z]]