Reaction of Mycobacterium tuberculosis cytochrome P450 enzymes with nitric oxide

Biochemistry. 2009 Feb 10;48(5):863-72. doi: 10.1021/bi801595t.


During the initial growth infection stage of Mycobacterium tuberculosis (Mtb), (*)NO produced by host macrophages inhibits heme-containing terminal cytochrome oxidases, inactivates iron/sulfur proteins, and promotes entry into latency. Here we evaluate the potential of (*)NO as an inhibitor of Mtb cytochrome P450 enzymes, as represented by CYP130, CYP51, and the two previously uncharacterized enzymes CYP125 and CYP142. Using UV-visible absorption, resonance Raman, and stopped-flow spectroscopy, we investigated the reactions of (*)NO with these heme proteins in their ferric resting form. (*)NO coordinates tightly to CYP125 and CYP142 (submicromolar) and with a lower affinity (micromolar) to CYP130 and CYP51. Anaerobic reduction of the ferric-NO species with sodium dithionite led to the formation of two spectrally distinct classes of five-coordinate ferrous-NO complexes. Exposure of these species to O(2) revealed that the ferrous-NO forms of CYP125 and CYP142 are labile and convert back to the ferric state within a few minutes, whereas ferrous CYP130 and CYP51 bind (*)NO almost irreversibly. This work clearly indicates that, at physiological concentrations (approximately 1 microM), (*)NO would impair the activity of CYP130 and CYP51, whereas CYP125 and CYP142 are more resistant. Selective P450 inhibition may contribute to the inhibitory effects of (*)NO on Mtb growth.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bacterial Proteins / metabolism*
  • Cattle
  • Cytochrome P-450 Enzyme System / metabolism*
  • Ferric Compounds / metabolism
  • Horses
  • Mycobacterium tuberculosis / enzymology*
  • Mycobacterium tuberculosis / growth & development
  • Nitric Oxide / biosynthesis
  • Nitric Oxide / metabolism*
  • Protein Binding
  • Reactive Nitrogen Species / biosynthesis
  • Reactive Nitrogen Species / metabolism
  • Recombinant Proteins / metabolism


  • Bacterial Proteins
  • CYP130 protein, M tuberculosis
  • Ferric Compounds
  • Reactive Nitrogen Species
  • Recombinant Proteins
  • Nitric Oxide
  • Cytochrome P-450 Enzyme System
  • cytochrome P-450 CYP51, Mycobacterium tuberculosis