title: Fatty acyl-CoA inhibition of beta-hydroxy-beta-methylglutaryl-CoA reductase activity.
abstract: The influence of the fatty acyl-CoA thioesters on rat liver microsomal hydroxymethylglutaryl-CoA reductase activity was tested in vitro to determine if the previously demonstrated inhibition of [14C]acetate incorporation into cholesterol is due to inhibition of this rate limiting step in cholesterol synthesis. The polyunsaturated fatty acyl-CoA thioesters caused the greatest inhibition of enzyme activity, 50 micron arachidonoyl-CoA inhibiting 67% and 5 micron inhibiting 22%. 50 micron linoleoyl-CoA inhibited 56% with the more saturated thioesters causing less inhibition. 50--100 micron free fatty acids, free CoA, cholesterol esters, phospholipids, carnitine derivatives, prostaglandins and non-specific detergents caused little or no inhibition of enzyme activity. Kinetic studies revealed the inhibition to be noncompetitive with respect to hydroxymethylglutaryl-CoA with a Ki for arachidonoyl CoA of 3.10 micron. Fatty acyl-CoA inhibition of in vitro cholesterol synthesis is due to inhibition of hydroxymethylglutaryl-CoA reductase activity. Variation in intracellular concentrations of fatty acyl-CoA thioesters may signficantly alter cholesterol synthesis.
mesh_terms: D000214:Acyl Coenzyme A / Q000494:pharmacology*; D000818:Animals; D001095:Arachidonic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D011458:Prostaglandins E / Q000494:pharmacology; D011460:Prostaglandins F / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D000214:Acyl Coenzyme A; D001095:Arachidonic Acids; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D011458:Prostaglandins E; D011460:Prostaglandins F