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Mycobacterium tuberculosis KatG is a peroxynitritase
N L Wengenack1, M P Jensen, F Rusnak
1Department of Biochemistry and Molecular Biology and Section of Hematology Research, Mayo Clinic and Foundation, Rochester, Minnesota, 55905, USA.
Biochemical and Biophysical Research Communications
|March 19, 1999
Summary
Mycobacterium tuberculosis KatG enzyme efficiently breaks down peroxynitrite, a harmful molecule found in macrophages. This newly identified peroxynitritase activity may help the bacteria survive within host cells.
Area of Science:
- Biochemistry
- Microbiology
- Enzymology
Background:
- Mycobacterium tuberculosis (Mtb) survives in the oxidative environment of human macrophages.
- Mtb is known to be susceptible to reactive nitrogen intermediates like peroxynitrite.
- The hemoprotein KatG is a known enzyme in Mtb with various functions.
Purpose of the Study:
- To investigate the potential role of Mycobacterium tuberculosis KatG as a peroxynitritase.
- To quantify the catalytic efficiency of KatG in decomposing peroxynitrite.
Main Methods:
- Enzymatic assays were performed to measure the reaction rate of KatG with peroxynitrite.
- Kinetic parameters, specifically the association rate constant (kapp), were determined at physiological conditions (pH 7.4 and 37°C).
Main Results:
- Mycobacterium tuberculosis KatG was found to be an efficient peroxynitritase.
- KatG exhibited a kapp of 1.4 x 10^5 M^-1s^-1 for peroxynitrite decomposition.
- This activity was observed at pH 7.4 and 37°C.
Conclusions:
- The hemoprotein KatG possesses significant peroxynitritase activity.
- This enzymatic function of KatG may contribute to the persistence of Mycobacterium tuberculosis within macrophages.
- KatG's ability to neutralize peroxynitrite adds to its known enzymatic repertoire.