Futile cycling by human microsomal cytochrome P450 enzymes within intact fission yeast cells

• Published in: Archives of biochemistry and biophysics Vol. 701; p. 108791
• Main Authors: Weldemichael, Dawit M., Zhou, Kun, Su, Shi-jia, Zhao, Lin, Marchisio, Mario Andrea, Bureik, Matthias
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15-04-2021
• Subjects: Cytochrome P-450 Enzyme System - genetics; Cytochrome P-450 Enzyme System - metabolism; Cytochrome P450; Flow cytometry; Futile cycling; Humans; Hydrogen Peroxide - metabolism; Microsomes - enzymology; Oxidative stress; Reactive oxygen species; Schizosaccharomyces - enzymology; Schizosaccharomyces - genetics; Superoxide anion; Superoxides - metabolism; Flow cytometry; Oxidative stress; Superoxide anion; Reactive oxygen species; Futile cycling; Cytochrome P450
• ISSN: 0003-9861; 1096-0384
• DOI: 10.1016/j.abb.2021.108791

Human cytochrome P450 enzymes (CYPs or P450s) are known to be reduced by their electron transfer partners in the absence of substrate and in turn to reduce other acceptor molecules such as molecular oxygen, thereby creating superoxide anions (O2−•). This process is known as futile cycling. Using our previously established fission yeast expression system we have monitored cells expressing each one of the 50 human microsomal CYPs in the absence of substrate for oxidation of dihydroethidium in living cells by flow cytometry. It was found that 38 of these display a statistically significant increase in O2−• production. More specifically, cells expressing some CYPs were found to be intermediate strength O2−• producers, which means that their effect was comparable to that of treatment with 3 mM H2O2. Cells expressing other CYPs had an even stronger effect, with those expressing CYP2B6, CYP5A1, CYP2A13, CYP51A1, or CYP1A2, respectively, being the strongest producers of O2−•.
Scheme of futile cycling of cytochrome P450 enzymes. [Display omitted]
•Cells expressing 38 out of 50 human microsomal CYPs displayed superoxide production.•Strongest superoxide production by cells expressing CYP2B6, CYP5A1, or CYP2A13.•No superoxide production by cells expressing CYP3A4 or CYP2E1.