Mycobacterium tuberculosis KatG catalyzes the activation of the antitubercular agent isoniazid to yield an inhibitor targeting enoyl reductase (InhA). However, no firm biochemical link between many KatG variants and isoniazid resistance has been established. In the present study, six distinct KatG variants identified in clinical Mycobacterium tuberculosis isolates resistant to isoniazid were ge...

Intracellular pathogenic bacteria, including Mycobacterium tuberculosis, frequently have multitiered defense mechanisms ensuring their survival in host phagocytic cells. One such defense determinant in M. tuberculosis is the katG gene, which encodes an enzyme with catalase, peroxidase, and peroxynitritase activities. KatG is considered to be important for protection against reactive oxygen and ...

The plasmid-borne Rhizobium etli katG gene encodes a dual-function catalase-peroxidase (KatG) (EC 1.11.1.7) that is inducible and heat-labile. In contrast to other rhizobia, katG was shown to be solely responsible for catalase and peroxidase activity in R. etli. An R. etli mutant that did not express catalase activity exhibited increased sensitivity to hydrogen peroxide (H(2)O(2)). Pre-exposure...

Catalase-peroxidase (KatG) from Mycobacterium tuberculosis is responsible for the activation of the antitubercular drug isonicotinic acid hydrazide (INH) and is important for survival of M. tuberculosis in macrophages. Characterization of the structure and catalytic mechanism of KatG is being pursued to provide insights into drug (INH) resistance in M. tuberculosis. Site-directed mutagenesis wa...

Although the major causes of isoniazid (INH) resistance in Mycobacterium tuberculosis are confined to structural mutations in katG and promoter mutations in the mabA-inhA operon, a significant proportion of INH-resistant strains have unknown resistance mechanisms. Recently, we identified a high-level INH-resistant M. tuberculosis clinical isolate, GB005, with no known resistance-associated muta...

Catalase-peroxidases (KatG) are bifunctional enzymes possessing both catalase and peroxidase activities. Three crystal structures of different KatGs revealed the presence of a novel Met-Tyr-Trp cross-link that has been suggested to impart catalatic activity to the KatGs. High-performance liquid chromatographic separation of the peptide fragments resulting from tryptic digestion of recombinant M...

Caulobacter crescentus is an obligate aerobe which is exposed to high concentrations of photosynthetic oxygen and low levels of nutrients in its aquatic environment. Physiological studies of oxidative and starvation stresses in C. crescentus were undertaken through a study of lacZ fusion and null mutant strains constructed from the cloned 5' end of katG, encoding a catalase-peroxidase. The katG...

Objective: The Rifampicin resistance and susceptibility of Mycobacterium tuberculosis are caused by mutations in the 81-base pair region of the rpoB gene encoding the b-subunit of RNA polymerase. Methods: Isoniazid resistance of M. tuberculosis is related to mutations in inha , oxyR and ahpC genes which 30 to 90 percent of Isoniazid resistance is occurred in 3015 codons of kat...

We used metalloregulated luciferase reporter fusions and spectroscopic quantification of soluble Hg(II) to determine that the hydroperoxidase-catalase, KatG, of Escherichia coli can oxidize monatomic elemental mercury vapor, Hg(0), to the water-soluble, ionic form, Hg(II). A strain with a mutation in katG and a strain overproducing KatG were used to demonstrate that the amount of Hg(II) formed ...

In order to probe the structure and function of the mycobacterial catalase-peroxidase enzyme (KatG), we employed a genetic approach using dominant-negative analysis of katG merodiploids. Transformation of Mycobacterium bovis BCG with various katG point mutants (expressed from low-copy-number plasmids) resulted in reductions in peroxidase and catalase activities as measured in cell extracts. The...