Ricerc@Sapienza

Cytochrome bd is a prokaryotic respiratory terminal oxidase phylogenetically unrelated to haem-copper oxidases. In addition to sustaining energy metabolism, this enzyme is implicated in bacterial protection against oxidative and nitrosative stress. Cytochrome bd is only found in prokaryotes and, as it promotes virulence in several pathogenic bacteria, it is currently recognized as a potential drug target.

Interaction of two redox enzymes of Escherichia coli, cytochrome bo3 and cytochrome bd-I, with ammonium sulfate/ammonia at pH 7.0 and 8.3 was studied using high-resolution respirometry and absorption spectroscopy. At pH 7.0, the oxygen reductase activity of none of the enzymes is affected by the ligand. At pH 8.3, cytochrome bo3 is inhibited by the ligand, with 40% maximum inhibition at 100 mM (NH4 )2SO4 . In contrast, the activity of cytochrome bd-I at pH 8.3 increases with increasing the ligand concentration, the largest increase (140%) is observed at 100 mM (NH4 )2SO4 .