2ccd: Difference between revisions
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==Overview== | ==Overview== | ||
Inhibition of the enzyme Mycobacterium tuberculosis InhA (enoyl-acyl, carrier protein reductase) due to formation of an isonicotinoyl-NAD adduct, (IN-NAD) from isoniazid (INH) and nicotinamide adenine dinucleotide, cofactor is considered central to the mode of action of INH, a first-line, treatment for tuberculosis infection. INH action against mycobacteria, requires catalase-peroxidase (KatG) function, and IN-NAD adduct formation, is catalyzed in vitro by M. tuberculosis KatG under a variety of, conditions, yet a physiologically relevant approach to the process has not, emerged that allows scrutiny of the mechanism and the origins of INH, resistance in the most prevalent drug-resistant strain bearing, KatG[S315T]. In this report, we describe how hydrogen peroxide, delivered, at very low ... [ | Inhibition of the enzyme Mycobacterium tuberculosis InhA (enoyl-acyl, carrier protein reductase) due to formation of an isonicotinoyl-NAD adduct, (IN-NAD) from isoniazid (INH) and nicotinamide adenine dinucleotide, cofactor is considered central to the mode of action of INH, a first-line, treatment for tuberculosis infection. INH action against mycobacteria, requires catalase-peroxidase (KatG) function, and IN-NAD adduct formation, is catalyzed in vitro by M. tuberculosis KatG under a variety of, conditions, yet a physiologically relevant approach to the process has not, emerged that allows scrutiny of the mechanism and the origins of INH, resistance in the most prevalent drug-resistant strain bearing, KatG[S315T]. In this report, we describe how hydrogen peroxide, delivered, at very low concentrations to ferric KatG, leads to efficient inhibition, of InhA due to formation of the IN-NAD adduct. The rate of adduct, formation mediated by wild-type KatG was about 20-fold greater than by the, isoniazid-resistant KatG[S315T] mutant under optimal conditions (H2O2, supplied along with NAD+ and INH). Slow adduct formation also occurs, starting with NADH and INH, in the presence of KatG even in the absence of, added peroxide, due to endogenous peroxide. The poor efficiency of the, KatG[S315T] mutant can be enhanced merely by increasing the concentration, of INH, consistent with this enzyme's reduced affinity for INH binding to, the resting enzyme and the catalytically competent enzyme intermediate, (Compound I). Origins of drug resistance in the KatG[S315T] mutant enzyme, are analyzed at the structural level through examination of the, three-dimensional X-ray crystal structure of the mutant enzyme. | ||
==About this Structure== | ==About this Structure== | ||
2CCD is a | 2CCD is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Mycobacterium_tuberculosis Mycobacterium tuberculosis] with HEM as [http://en.wikipedia.org/wiki/ligand ligand]. Structure known Active Site: AC1. Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=2CCD OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: peroxidase]] | [[Category: peroxidase]] | ||
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Revision as of 13:43, 5 November 2007
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CRYSTAL STRUCTURE OF THE CATALASE-PEROXIDASE (KATG) AND S315T MUTANT FROM MYCOBACTERIUM TUBERCULOSIS
OverviewOverview
Inhibition of the enzyme Mycobacterium tuberculosis InhA (enoyl-acyl, carrier protein reductase) due to formation of an isonicotinoyl-NAD adduct, (IN-NAD) from isoniazid (INH) and nicotinamide adenine dinucleotide, cofactor is considered central to the mode of action of INH, a first-line, treatment for tuberculosis infection. INH action against mycobacteria, requires catalase-peroxidase (KatG) function, and IN-NAD adduct formation, is catalyzed in vitro by M. tuberculosis KatG under a variety of, conditions, yet a physiologically relevant approach to the process has not, emerged that allows scrutiny of the mechanism and the origins of INH, resistance in the most prevalent drug-resistant strain bearing, KatG[S315T]. In this report, we describe how hydrogen peroxide, delivered, at very low concentrations to ferric KatG, leads to efficient inhibition, of InhA due to formation of the IN-NAD adduct. The rate of adduct, formation mediated by wild-type KatG was about 20-fold greater than by the, isoniazid-resistant KatG[S315T] mutant under optimal conditions (H2O2, supplied along with NAD+ and INH). Slow adduct formation also occurs, starting with NADH and INH, in the presence of KatG even in the absence of, added peroxide, due to endogenous peroxide. The poor efficiency of the, KatG[S315T] mutant can be enhanced merely by increasing the concentration, of INH, consistent with this enzyme's reduced affinity for INH binding to, the resting enzyme and the catalytically competent enzyme intermediate, (Compound I). Origins of drug resistance in the KatG[S315T] mutant enzyme, are analyzed at the structural level through examination of the, three-dimensional X-ray crystal structure of the mutant enzyme.
About this StructureAbout this Structure
2CCD is a Single protein structure of sequence from Mycobacterium tuberculosis with HEM as ligand. Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Hydrogen peroxide-mediated isoniazid activation catalyzed by Mycobacterium tuberculosis catalase-peroxidase (KatG) and its S315T mutant., Zhao X, Yu H, Yu S, Wang F, Sacchettini JC, Magliozzo RS, Biochemistry. 2006 Apr 4;45(13):4131-40. PMID:16566587
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