Pseudomonas aeruginosacytochrome P450 CYP168A1 is a fatty acid hydroxylase that metabolizes arachidonic acid to the vasodilator 19-HETE

Abstract

Pseudomonas aeruginosa is a gram-negative opportunistic human pathogen that is highly prevalent in individuals with cystic fibrosis (CF). A major problem in treating CF patients infected with P. aeruginosa is the development of antibiotic resistance. Therefore, the identification of novel P. aeruginosa antibiotic drug targets is of the upmost urgency. The genome of P. aeruginosa contains four putative cytochrome P450 enzymes (CYPs) of unknown function that have never before been characterized. Analogous to some of the CYPs from M. tuberculosis, the P. aeruginosa CYPs may be important for growth and colonization of the CF patient’s lung. In this study, we cloned, expressed, and characterized CYP168A1 from P. aeruginosa and identified it as a sub-terminal fatty acid hydroxylase. Spectral binding data and computational modeling of substrates and inhibitors suggest that CYP168A1 has a large, expansive active site preferring long chain fatty acids and large hydrophobic inhibitors. Furthermore, metabolism experiments confirm that the enzyme is capable of hydroxylating arachidonic acid, an important inflammatory signaling molecule present in abundance in the CF lung, to 19-hydroxyeicosatetraenoic acid (19-HETE; Km = 41.1 µM, Vmax = 222 pmol/min/nmol P450), a potent vasoconstrictor which may play a role in the pathogen’s ability to colonize the mammalian lung. Metabolism of arachidonic acid is subject to substrate inhibition and is also inhibited by the presence of ketoconazole. This study points to the discovery of a new potential drug target that may be of utility in treating drug resistant P. aeruginosa.