Substrate binding site of microsomal cytochrome P-450 directly faces membrane lipids.
Cytochrome P-450, purified from liver microsomes of phenobarbital-treated rabbits, was incorporated into dimyristoylphosphatidylcholine liposomes. The binding of benzphetamine to the liposome-bound cytochrome P-450 was examined by measuring the benzphetamine-induced spectral change at various temperatures. The van't Hoff plot of the apparent spectral dissociation constant showed a distinct break at the temperature of phase transition of the synthetic lipid. On the other hand, no such break was observed for benzphetamine binding to microsomal bound cytochrome P-450. These results suggest that the substrate binding site of cytochrome P-450 is embedded in the apolar interior of phospholipid bilayer membranes.
D000818:Animals; D001589:Benzphetamine / Q000378:metabolism*; D001665:Binding Sites; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004134:Dimyristoylphosphatidylcholine / Q000378:metabolism; D008051:Lipid Bilayers / Q000378:metabolism*; D008081:Liposomes / Q000378:metabolism; D008563:Membrane Lipids / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D010627:Phenethylamines / Q000378:metabolism*; D011817:Rabbits; D013053:Spectrophotometry; D013696:Temperature
D008051:Lipid Bilayers; D008081:Liposomes; D008563:Membrane Lipids; D010627:Phenethylamines; D001589:Benzphetamine; D003577:Cytochrome P-450 Enzyme System; D004134:Dimyristoylphosphatidylcholine