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1h1m

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[[Image:1h1m.gif|left|200px]]
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{{Seed}}
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[[Image:1h1m.png|left|200px]]
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{{STRUCTURE_1h1m| PDB=1h1m | SCENE= }}
{{STRUCTURE_1h1m| PDB=1h1m | SCENE= }}
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'''CRYSTAL STRUCTURE OF QUERCETIN 2,3-DIOXYGENASE ANAEROBICALLY COMPLEXED WITH THE SUBSTRATE KAEMPFEROL'''
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===CRYSTAL STRUCTURE OF QUERCETIN 2,3-DIOXYGENASE ANAEROBICALLY COMPLEXED WITH THE SUBSTRATE KAEMPFEROL===
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==Overview==
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Quercetin 2,3-dioxygenase (2,3QD) is the only firmly established copper dioxygenase known so far. Depending solely on a mononuclear Cu center, it catalyzes the breakage of the O-heterocycle of flavonols, producing more easily degradable phenolic carboxylic acid ester derivatives. In the enzymatic process, two CC bonds are broken and concomitantly carbon monoxide is released. The x-ray structures of Aspergillus japonicus 2,3QD anaerobically complexed with the substrate kaempferol and the natural substrate quercetin have been determined at 1.90- and 1.75-A resolution, respectively. Flavonols coordinate to the copper ion as monodentate ligands through their 3OH group. They occupy a shallow and overall hydrophobic cavity proximal to the metal center. As a result of a van der Waals contact between the most outward flavonol A-ring and Pro(164), a flexible loop in front of the active site becomes partly ordered. Interestingly, flavonols bound to 2,3QD are bent at the C2 atom, which is pyramidalized. The increased local sp(3) character at this atom may stabilize a carbon-centered radical activated for dioxygen attack. Glu(73) coordinates the copper through its O epsilon 1 atom. The short distance of about 2.55 A between its O epsilon 2 atom and the flavonol O3 atom suggests that a hydrogen bond exists between the two atoms, indicating that Glu(73) can act as a base in flavonol deprotonation and that it retains the proton. Structure-based geometric considerations indicate O(2) binding to the flavonol C2 atom as the preferred route for flavonol dioxygenation.
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(as it appears on PubMed at http://www.pubmed.gov), where 12486225 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12486225}}
==About this Structure==
==About this Structure==
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[[Category: Flavonol]]
[[Category: Flavonol]]
[[Category: Oxidoreductase]]
[[Category: Oxidoreductase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 18:18:08 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 06:28:09 2008''

Revision as of 03:28, 1 July 2008

Image:1h1m.png

Template:STRUCTURE 1h1m

CRYSTAL STRUCTURE OF QUERCETIN 2,3-DIOXYGENASE ANAEROBICALLY COMPLEXED WITH THE SUBSTRATE KAEMPFEROL

Template:ABSTRACT PUBMED 12486225

About this Structure

1H1M is a Single protein structure of sequence from Aspergillus japonicus. Full crystallographic information is available from OCA.

Reference

Anaerobic enzyme.substrate structures provide insight into the reaction mechanism of the copper-dependent quercetin 2,3-dioxygenase., Steiner RA, Kalk KH, Dijkstra BW, Proc Natl Acad Sci U S A. 2002 Dec 24;99(26):16625-30. Epub 2002 Dec 16. PMID:12486225

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