Roles of phospholipid and detergent in soluble protein activation of squalene epoxidase.
"Soluble protein factor" (SPF) from hog liver stimulates hepatic microsome-associated squalene epoxidase in the presence of phosphatidylglycerol or phosphatidylserine. When SPF and phosphatidylglycerol are preincubated for 30 min at 37 degrees C before addition to the epoxidase system, this stimulation is abolished. On Sephadex chromatography of the protein--phospholipid mixture, both components appear in the void volume, whereas SPF alone is retarded on the column. These results suggest formation of a SPF--phosphatidylglycerol complex. Treatment of the complex with Tween 80 restores the stimulatory effects of SPF on squalene epoxidase. The stimulation of microsomal squalene epoxidase by SPF was abolished by pretreatment of the membrane with low concentrations of deoxycholate or by solubilizing the enzyme with Triton X-100, implying that an intact membrane system is required for SPF sensitivity. SPF has been purified 1200-fold from hog liver.
D000818:Animals; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D008110:Liver Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D008862:Microsomes, Liver / Q000201:enzymology*; D017830:Octoxynol; D010105:Oxygenases / Q000378:metabolism*; D010715:Phosphatidylglycerols / Q000494:pharmacology*; D010718:Phosphatidylserines / Q000494:pharmacology*; D011092:Polyethylene Glycols / Q000494:pharmacology; D011136:Polysorbates / Q000494:pharmacology; D050603:Squalene Monooxygenase; D013552:Swine
D008110:Liver Extracts; D010715:Phosphatidylglycerols; D010718:Phosphatidylserines; D011136:Polysorbates; D011092:Polyethylene Glycols; D017830:Octoxynol; D010105:Oxygenases; D050603:Squalene Monooxygenase