title: Effect of diabetes on partially purified hepatic cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme of bile acid biosynthesis.
abstract: The effect of diabetes on the activity of hepatic cholesterol 7 alpha-hydroxylase (CH-7 alpha) was studied in reconstituted systems using partially purified cytochrome P-450 (P-450) from control and diabetic rat livers. With both preparations, the rate of product formation increased when the amount of P-450 in the incubations was increased. However, the increase in the rate of product formation was greater with the control P-450. When varying levels of dithiothreitol (DTT) were added to the incubations, the specific activity of the control P-450 was found to be directly proportional to the concentration of DTT. However, DTT did not have any consistent effect on the specific activity of the diabetic P-450. Finally, while 25 mM NaF in the incubation medium had minimal effect on the specific activity of the control P-450, the specific activity of the diabetic P-450 increased by 32% in the presence of 25 mM NaF. These studies have shown some important differences in the properties of CH-7 alpha in control and diabetic animals and emphasize the need to study the enzyme under more defined conditions.
mesh_terms: D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis*; D002790:Cholesterol 7-alpha-Hydroxylase / Q000302:isolation & purification / Q000378:metabolism*; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D004229:Dithiothreitol / Q000494:pharmacology; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D009251:NADPH-Ferrihemoprotein Reductase / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D013250:Steroid Hydroxylases / Q000378:metabolism*
chemical_list: D001647:Bile Acids and Salts; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; D002790:Cholesterol 7-alpha-Hydroxylase; D009251:NADPH-Ferrihemoprotein Reductase; D004229:Dithiothreitol