scholarly journals Nitric Oxide Generated from Isoniazid Activation by KatG: Source of Nitric Oxide and Activity against Mycobacterium tuberculosis

2004 ◽  
Vol 48 (8) ◽  
pp. 3006-3009 ◽  
Author(s):  
Graham S. Timmins ◽  
Sharon Master ◽  
Frank Rusnak ◽  
Vojo Deretic
Keyword(s):  
Nitric Oxide ◽  
Mycobacterium Tuberculosis ◽  
Isonicotinic Acid ◽  
Acid Hydrazide ◽  
Antimycobacterial Activity ◽  
Paramagnetic Resonance ◽  
Catalase Peroxidase ◽  
Resonance Spin ◽  
Electron Paramagnetic ◽  
Mycobacterial Protein

ABSTRACT Isonicotinic acid hydrazide (INH) is a frontline antituberculosis agent. Once taken up by Mycobacterium tuberculosis, INH requires activation by the catalase-peroxidase KatG, converting INH from its prodrug form into a range of bactericidal reactive species. Here we used 15N-labeled INH together with electron paramagnetic resonance spin trapping techniques to demonstrate that nitric oxide (NO˙) is generated from oxidation at the hydrazide nitrogens during the activation of INH by M. tuberculosis KatG. We also observed that a specific scavenger of NO˙ provided protection against the antimycobacterial activity of INH in bacterial culture. No significant increases in mycobacterial protein nitration were detected, suggesting that NO˙ and not peroxynitrite, a nitrating metabolite of NO·, is involved in antimycobacterial action. In conclusion, INH-derived NO· has biological activity, which directly contributes to the antimycobacterial action of INH.

scholarly journals 216 GHz Electron Paramagnetic Resonance of Mycobacterium Tuberculosis Catalase-Peroxidase: The Role of the Arg418 Residue

2018 ◽  
Author(s):  
Matt Bawn ◽  
Jurek Krzystek ◽  
Richard Magliozzo
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Catalytic Mechanism ◽  
Structural Features ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Mutant Proteins ◽  
Catalase Peroxidase ◽  
Covalently Linked ◽  
Electron Paramagnetic

ABSTRACTThe catalase-peroxidase protein from Mycobacterium tuberculosis contains a variety of unique structural features including a covalently-linked three amino acid adduct capable of hosting a tyrosine-based radical. Previous work has demonstrated that the Arg418 residue is essential for the catalse but not the peroxidase activity of the protein and crystallography has indicated the residue to be capable of adopting two conformations relative to the adduct-radical. In the present work the WT and Arg418Leu mutant proteins were investigated using high-field electron magnetic resonance spectroscopy. Different sets of g-values were found for each protein indicating different paramagnetic environments. Quantum chemical calculations of model structures were undertaken to elucidate the geometrical environment of the radical. It is proposed that the two sets of g-values correspond to the two conformations of the Arg418 residue. The implications for the catalytic mechanism are discussed.

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