Membrane Phospholipid Augments Cytochrome P4501a Enzymatic Activity by Modulating Structural Conformation during Detoxification of Xenobiotics

Abstract

Cytochrome P450 is a superfamily of membrane-bound hemoprotein that gets involved with the degradation of xenobiotics and internal metabolites. Accumulated body of evidence indicates that phospholipids play a crucial role in determining the enzymatic activity of cytochrome P450 in the microenvironment by modulating its structure during detoxification; however, the structure-function relationship of cytochrome P4501A, a family of enzymes responsible for degrading lipophilic aromatic hydrocarbons, is still not well defined. Inducibility of cytochrome P4501A in cultured catfish hepatocytes in response to carbofuran, a widely used pesticide around the world, was studied earlier in our laboratory. In this present investigation, we observed that treating catfish with carbofuran augmented total phospholipid in the liver. We examined the role of phospholipid on the of cytochrome P4501A-marker enzyme which is known as ethoxyresorufin-O-deethylase (EROD) in the context of structure and function. We purified the carbofuran-induced cytochrome P4501A protein from catfish liver. Subsequently, we examined the enzymatic activity of purified P4501A protein in the presence of phospholipid, and studied how the structure of purified protein was influenced in the phospholipid environment. Membrane phospholipid appeared to accelerate the enzymatic activity of EROD by changing its structural conformation and thus controlling the detoxification of xenobiotics. Our study revealed the missing link of how the cytochrome P450 restores its enzymatic activity by changing its structural conformation in the phospholipid microenvironment.

An Integrated Biomarker Approach Using Flounder to Improve Chemical Risk Assessments in the Heavily Polluted Seine Estuary

“…The Douarnenez fish also displayed a positive correlation between SPG and liver EROD activity. In the context of a weak pollution by organic pollutants, it seems that the increase of sphingolipids particularly located in endoplasmic reticulum could increase the catalytic activity of the cytochrome P4501A, as seen previously [81,82].…”

“…The specific lipid composition of rafts allows for more xenobiotics and endogenous substrate metabolism by increased binding efficiency between CYP1A2 and CPR (NADPH-cytochrome P450 reductase) [81]. Membrane phospholipids seem to accelerate the enzymatic activity of cytochrome P4501A by changing its structural conformation, thus controlling the detoxification of xenobiotics [82]. Complex sphingolipids associated with sterols are essential for maintaining endoplasmic reticulum homeostasis, and perturbation in sphingolipid levels activates an endoplasmic reticulum stress-mediated to propagate apoptotic signals to the mitochondria [83].…”

The Localization of Cytochrome P450s CYP1A1 and CYP1A2 into Different Lipid Microdomains Is Governed by Their N-terminal and Internal Protein Regions

“…These monooxygenase reactions require the substrate molecule, molecular oxygen, and electrons. The electrons are relayed from the reduced cofactors, NADPH and NADH, to the P450s by the redox partners, CPR, and cytochrome b 5 . The lipid bilayer of cell membranes is composed of numerous species of phospholipids.…”

Liposomes modified with cardiolipin can act as a platform to regulate the potential flux of NADP + -dependent isocitrate dehydrogenase

“…In general, the function of a protein or enzyme is strongly related to its conformation ( Ghosh and Ray, 2013 ). It is expected that the regulation of ICDH activity could be induced by its conformational change at the liposome membrane surface.…”