Differences in mechanisms of modulation between rat liver cholesterol 7 alpha-hydroxylase and HMG-CoA reductase.
The effects of microsomal HMG-CoA reductase kinase, cytosolic phosphoprotein phosphatase and cytosolic, thiol-dependent cholesterol 7 alpha-hydroxylase stimulatory protein on purified cholesterol 7 alpha-hydroxylase and HMG-CoA reductase from rat liver were compared. Neither HMG-CoA reductase kinase nor phosphoprotein phosphatase had any significant effect on cholesterol 7 alpha-hydroxylase activity. They inhibited and stimulated, respectively, the activity of HMG-CoA reductase. The purified cytosolic protein which stimulated cholesterol 7 alpha-hydroxylase threefold in the presence of glutathione had no effect on HMG-CoA reductase. The results show that there are separate intracellular systems for modulation of cholesterol 7 alpha-hydroxylase and HMG-CoA reductase.
Lidström-Olsson
B
B
D000818:Animals; D002790:Cholesterol 7-alpha-Hydroxylase / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005978:Glutathione / Q000494:pharmacology; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D051381:Rats; D013250:Steroid Hydroxylases / Q000378:metabolism*
D003577:Cytochrome P-450 Enzyme System; D006903:Hydroxymethylglutaryl CoA Reductases; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase; D010749:Phosphoprotein Phosphatases; D005978:Glutathione