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| [[Image:1dj5.gif|left|200px]] | | {{Seed}} |
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| {{STRUCTURE_1dj5| PDB=1dj5 | SCENE= }} | | {{STRUCTURE_1dj5| PDB=1dj5 | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF R48A MUTANT OF CYTOCHROME C PEROXIDASE WITH N-HYDROXYGUANIDINE BOUND'''
| | ===CRYSTAL STRUCTURE OF R48A MUTANT OF CYTOCHROME C PEROXIDASE WITH N-HYDROXYGUANIDINE BOUND=== |
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| ==Overview==
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| Heme enzymes are capable of catalyzing a range of oxidative chemistry with high specificity, depending on the surrounding protein environment. We describe here a reaction catalyzed by a mutant of cytochrome c peroxidase, which is similar but distinct from those catalyzed by nitric-oxide synthase. In the R48A mutant, an expanded water-filled cavity was created above the distal heme face. N-hydroxyguanidine (NHG) but not guanidine was shown to bind in the cavity with K(d) = 8.5 mM, and coordinate to the heme to give a low spin state. Reaction of R48A with peroxide produced a Fe(IV)=O/Trp(.+) center capable of oxidizing either NHG or N(omega)-hydroxyarginine (NHA), but not arginine or guanidine, by a multi-turnover catalytic process. Oxidation of either NHG or NHA by R48A did not result in the accumulation of NO, NO(2)(-), NO(3)(-), urea, or citrulline, but instead afforded a yellow product with absorption maxima of 257 and 400 nm. Mass spectrometry of the derivatized NHA products identified the yellow species as N-nitrosoarginine. We suggest that a nitrosylating agent, possibly derived from HNO, is produced by the oxidation of one molecule of substrate. This then reacts with a second substrate molecule to form the observed N-nitroso products. This complex chemistry illustrates how the active sites of enzymes such as nitric-oxide synthase may serve to prevent alternative reactions from occurring, in addition to enabling those desired.
| | The line below this paragraph, {{ABSTRACT_PUBMED_10722697}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 10722697 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_10722697}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Heme enzyme]] | | [[Category: Heme enzyme]] |
| [[Category: Oxidoreductase]] | | [[Category: Oxidoreductase]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 13:54:20 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 23:08:39 2008'' |
