ML236B is a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoA reductase) (EC 1.1.1.34), the major regulatory enzyme in cholesterol biosynthesis. This compound inhibits cell growth when present in the culture medium of CHO-K1 cells at a concentration as low as 0.1 pg/ml. Addition of the product of the HMG-CoA reductase reaction, mevalonate, to the culture me...

In previous investigations, we have found that the liver appears to be the major source of cholesterol in the human fetus, and, in particular, a principal source of circulating low density lipo-protein-cholesterol (LDL-C). LDL-C plasma levels are low in the normal fetus, most likely due to the rapid uptake and metabolism by the fetal adrenal as precursor for steroid hormone biosynthesis. In con...

The discovery of the low density lipoprotein (LDL) receptor 11 years ago and the subsequent elucidation of its mode of action in the cell and in the body have provided a conceptual framework for understanding the mechan: ns that control the concentration of the most a b u n-h t cholesterol-carrying lipoprotein in human blood. Study of the LDL receptor has taught us that human and animal cells p...

Phenylmethylsulfonyl fluoride (PMSF), a reagent commonly employed for the inhibition of serine proteases, has been found to cause significant inhibition of the incorporation of labeled acetate, but not mevalonate, into nonsaponifiable lipid and digitonin-precipitable sterols in the 10,000 X g supernatant fraction of rat liver homogenate preparations. In two experiments, the extent of inhibition...

The human pathogen Staphylococcus aureus does not utilize the glutathione thiol/disulfide redox system employed by eukaryotes and many bacteria. Instead, this organism produces CoA as its major low molecular weight thiol. We report the identification and purification of the disulfide reductase component of this thiol/disulfide redox system. Coenzyme A disulfide reductase (CoADR) catalyzes the s...

Microbiology, University of Alberta, Edmonton, Alberta T6G 2E9, Canada polyhydroxyalkanoate (PHA) in mutant Azotobacter vinelandii UWD, the kinetic properties of 3-ketothiolase, acetoacetyl-CoA reductase, and /3hydroxybutyrate dehydrogenase were examined. The regulatiorn of the condensation of acetyl-CoA mediated by 3-ketothiolase was narmal, in that it was negatively regulated by free CoA, but...

A somatic cell mutant of the CHO-K1 cell selected to be resistant to the killing effects of 25-hydroxycholesterol in the absence of cholesterol is shown to be defective in the inhibition of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity by 25-hydroxycholesterol, cholesterol, and lipoproteins, thus maintaining the enzyme activity found in cells in the absence of exogenous sterol con...

Lovastatin, a potent competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity, was used to study the regulation of cholesterol metabolism and the basolateral-membrane secretion of triacylglycerol and cholesterol in the human intestinal cell line CaCo-2. At 0.1 microgram/ml, lovastatin decreased 3H2O incorporation into cholesterol by 71%. In membranes prepared from ce...

The regulation of hepatic and intestinal 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase and acyl-CoA; cholesterol acyltransferase (ACAT) activities by dietary fish oil was examined in the rabbit. Rabbits were fed 10% menhaden oil or menhaden oil plus 1% cholesterol for 14 days. They were compared with animals fed a control diet or one enriched with long-chain saturated fats consisting of 10...

Human high density lipoproteins (HDLs), a heterogeneous class of particles which is mitogenic for bovine vascular endothelial cells, stimulate the 3-hydroxy-3methylglutaryl coenzyme A (HMG-CoA) reductase activity present in both actively proliferating sparse endothelial cells and in nondividing confluent cultures. Kinetics of the enzyme response to HDLs was studied in confluent cells, and the r...