Formation of P450·P450 complexes and their effect on P450 function

Abstract

Cytochromes P450 (P450) are membrane-bound enzymes that catalyze the monooxygenation of a diverse array of xenobiotic and endogenous compounds. The P450s responsible for foreign compound metabolism generally are localized in the endoplasmic reticulum of the liver, lung and small intestine. P450 enzymes do not act alone but require an interaction with other electron transfer proteins such as NADPH-cytochrome P450 reductase (CPR) and cytochrome b5. Because P450s are localized in the endoplasmic reticulum with these and other ER-resident proteins, there is a potential for protein-protein interactions to influence P450 function. There has been increasing evidence that P450 enzymes form complexes in the ER, with compelling support that formation of P450•P450 complexes can significantly influence their function. Our goal is to review the research supporting the formation of P450•P450 complexes, their specificity, and how drug metabolism may be affected. This review describes the potential mechanisms by which P450s may interact, and provides evidence to support each of the possible mechanisms. Additionally, evidence for the formation of both heteromeric and homomeric P450 complexes are reviewed. Finally, direct physical evidence for P450 complex formation in solution and in membranes is summarized, and questions directing the future research of functional P450 interactions are discussed with respect to their potential impact on drug metabolism.

Combinatorial biosynthesis of sapogenins and saponins in Saccharomyces cerevisiae using a C-16α hydroxylase from Bupleurum falcatum

“…S4). Although the actual CPR:P450 ratios were not biochemically measured, the product accumulation observed after attempting to alter the ratios through the vector copy numbers is in line with the P450 being in excess of the CPR, as reported for mammalian and yeast systems (34) (Fig. S5).…”

“…The endoplasmic reticulum (ER)-localized CPRs are flavoproteins that serve as electron donor proteins for several ER oxygenases, including P450s (33). Optimal interaction between CPR and P450 is essential to allow the reducing equivalents from NADPH to pass from the CPR to the P450 and guarantee P450 functionality (34). To assess whether different CPR:P450 ratios would affect CYP716Y1 performance, we generated strains expressing CYP716Y1 from a high-copy number plasmid together with AtATR1 from either an integrated (1 copy per cell), low-copy (3-5 copies per cell), or high-copy (10-40 copies per cell) number plasmid.…”

Interactions among Cytochromes P450 in Microsomal Membranes

“…Besides evidence of homooligomerization of various P450 species (10,12,15,(17)(18)(19)(20)(21)(22)(23), there are also multiple indications of interactions between dis-similar P450s in membranes of proteoliposomes (13), microsomes (14), and living cells (16). The body of evidence of profound functional effects exerted by P450-P450 interactions continues to grow (24,25).…”

Liver microsomal lipid enhances the activity and redox coupling of colocalized cytochrome P450 reductase‐cytochrome P450 3A4 in nanodiscs

“…Although the fundamentally conserved reaction mechanism of this coupled enzyme system is understood in some detail 4, 5, 6, 7, the influence of the complex composition of the surrounding membrane on catalytic activity is poorly understood. Furthermore, comparative studies of CYP catalytic activity are complicated by the various effects of homotropic and heterotropic cooperativity of substrate binding, homomeric and heteromeric complex formation, and different CPR : CYP ratios 8, 9, 10.…”