Squalene Epoxidase of Rat Liver*
نویسنده
چکیده
The microsomal enzyme system from rat liver which catalyzes the epoxidation of squalene to 2,3-oxidosqualene (squalene epoxidase) has been investigated further with 10 ,ll-dihydrosqualene as the artacial substrate. Liver supernatant contributes two essential components to the epoxidase system, one heat stable and the other heat labile (YAMAMOTO, S., AND BLOCH, K. (1970) J. Biol. Chem. 245, 1670). The requirement for the heat-stable factor can be fully met by phosphatidylserine, phosphatidylglycerol, or phos phatidylinositol and partially by other phospholipids. The heat-labile supernatant component is a protein, molecular weight 44,000, which has been purified 84-fold. Supernatant protein factor fails to bind either squalene, 10 ,llDihydrosqualene, or 2,3-oxidosqualene as judged by chromatography of mixtures on Sephadex. In an epoxidase system reconstituted from washed microsomes, supernatant protein factor, and phosphatidylserine, FAD raises enzyme activity by about 50%.
منابع مشابه
Studies on Squalene Epoxidase of Rat Liver*
Rat liver microsomes previously heated to 50” for 5 mm accumulate 2,3-oxidosqualene on incubation with squalene. Squalene epoxidase activity can be assayed either with squalene and heated microsomes or with lO,ll-dihydrosqualene and intact microsomes. In common with other monooxygenases, the epoxidase requires TPNH and molecular oxygen. Both a soluble fraction of rat liver and microsomes are ne...
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Squalene epoxidase activity has been studied in cell-free preparations of Chinese hamster ovary (CHO) cells and rat liver. In contrast to rat liver microsomal squalene epoxidase, the enzyme of CHO cells is only slightly activated by the autologous cytosolic fraction, whereas phosphatidylglycerol or rat liver cytosolic preparations are potent stimulators of this enzyme. Triton X-100, a known sti...
متن کاملStudies on squalene epoxidase of rat liver.
Rat liver microsomes previously heated to 50” for 5 mm accumulate 2,3-oxidosqualene on incubation with squalene. Squalene epoxidase activity can be assayed either with squalene and heated microsomes or with lO,ll-dihydrosqualene and intact microsomes. In common with other monooxygenases, the epoxidase requires TPNH and molecular oxygen. Both a soluble fraction of rat liver and microsomes are ne...
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