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| [[Image:1czf.gif|left|200px]] | | {{Seed}} |
| | [[Image:1czf.png|left|200px]] |
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| {{STRUCTURE_1czf| PDB=1czf | SCENE= }} | | {{STRUCTURE_1czf| PDB=1czf | SCENE= }} |
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| '''ENDO-POLYGALACTURONASE II FROM ASPERGILLUS NIGER'''
| | ===ENDO-POLYGALACTURONASE II FROM ASPERGILLUS NIGER=== |
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| ==Overview==
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| Polygalacturonases specifically hydrolyze polygalacturonate, a major constituent of plant cell wall pectin. To understand the catalytic mechanism and substrate and product specificity of these enzymes, we have solved the x-ray structure of endopolygalacturonase II of Aspergillus niger and we have carried out site-directed mutagenesis studies. The enzyme folds into a right-handed parallel beta-helix with 10 complete turns. The beta-helix is composed of four parallel beta-sheets, and has one very small alpha-helix near the N terminus, which shields the enzyme's hydrophobic core. Loop regions form a cleft on the exterior of the beta-helix. Site-directed mutagenesis of Asp(180), Asp(201), Asp(202), His(223), Arg(256), and Lys(258), which are located in this cleft, results in a severe reduction of activity, demonstrating that these residues are important for substrate binding and/or catalysis. The juxtaposition of the catalytic residues differs from that normally encountered in inverting glycosyl hydrolases. A comparison of the endopolygalacturonase II active site with that of the P22 tailspike rhamnosidase suggests that Asp(180) and Asp(202) activate the attacking nucleophilic water molecule, while Asp(201) protonates the glycosidic oxygen of the scissile bond.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10521427}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10521427 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10521427}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Santen, Y van.]] | | [[Category: Santen, Y van.]] |
| [[Category: Beta helix]] | | [[Category: Beta helix]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:16:26 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 21:51:51 2008'' |
