title: Membrane properties induced by anionic phospholipids and phosphatidylethanolamine are critical for the membrane binding and catalytic activity of human cytochrome P450 3A4.
abstract: Human cytochrome P450 (CYP) 3A4, a membrane anchoring protein, is the major CYP enzyme present in both liver and small intestine. The enzyme plays a major role in the metabolism of many drugs and procarcinogens. The roles of individual phospholipids and membrane properties in the catalytic activity, membrane binding, and insertion into the membrane of CYP3A4 are poorly understood. Here we report that the catalytic activity of testosterone 6beta-hydroxylation, membrane binding, and membrane insertion of CYP3A4 increase as a function of anionic phospholipid concentration in the order phosphatidic acid (PA) > phosphatidylserine (PS) in a binary system of phosphatidylcholine (PC)/anionic phospholipid and as a function of phosphatidylethanolamine (PE) content in ternary systems of PC/PE/PA or PC/PE/PS having a fixed concentration of anionic phospholipids. These results suggest that PA and PE might help the binding of CYP3A4 to the membrane and the interaction with NPR. Cytochrome b(5) (b(5)) and apolipoprotein b(5) further enhanced the testosterone 6beta-hydroxylation activities of CYP3A4 in all tested phospholipids vesicles with various compositions. Phospholipid-dependent changes of the CYP3A4 conformation were also revealed by altered Trp fluorescence and CD spectra. We also found that PE induced the formation of anionic phospholipid-enriched domains in ternary systems using extrinsic fluorescent probes incorporated into lipid bilayers. Taken together, it can be suggested that the chemical and physical properties of membranes induced by anionic phospholipids and PE are critical for the membrane binding and catalytic activity of CYP3A4.
authors.affiliation: Department of Genetic Engineering, Paichai University, Taejon 302-735, Korea.
authors.forename: Keon-Hee
authors.initials: KH
authors.lastname: Kim
authors.forename: Taeho
authors.initials: T
authors.lastname: Ahn
authors.forename: Chul-Ho
authors.initials: CH
authors.lastname: Yun
mesh_terms: D000838:Anions; D001051:Apoenzymes / Q000737:chemistry; D002384:Catalysis; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D015786:Cytochromes b5 / Q000737:chemistry; D006801:Humans; D008051:Lipid Bilayers / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D009249:NADP / Q000737:chemistry; D009251:NADPH-Ferrihemoprotein Reductase / Q000737:chemistry; D010084:Oxidation-Reduction; D010712:Phosphatidic Acids / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013250:Steroid Hydroxylases / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D000838:Anions; D001051:Apoenzymes; D008051:Lipid Bilayers; D008565:Membrane Proteins; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010743:Phospholipids; C483858:phosphatidylethanolamine; D009249:NADP; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C022657:steroid hormone 6-beta-hydroxylase; C510163:CYP3A4 protein, human; D009251:NADPH-Ferrihemoprotein Reductase