Mycobacterium tuberculosis KatG is a peroxynitritase

Mycobacterium tuberculosis resides within the highly oxidative environment of the human macrophage and previous reports have indicated that these myco bacteria are susceptible to reactive nitrogen intermediates including perox ynitrite. This work provides evidence that the Mycobacterium tuberculosis h emoprotein KatG acts as an efficient peroxynitritase exhibiting a k(app) of 1.4 x 10(5) M(-1)s(-1) for peroxynitrite decomposition at pH 7.4 and 37 de grees C. The ability of KatG to act as a peroxynitritase adds to its growin g list of enzymatic activities and may in part explain the ability of Mycob acterium tuberculosis to persist in macrophages. (C) 1999 Academic Press.