ABSTRACT
Heat-stable rat liver cytosolic proteins that stimulate triacylglycerol synthesis catalyzed by adipose tissue or liver microsomal enzymes have been isolated in a highly purified state. Their molecular weight ranges were found to be 35 000 - 45 000, 20 000 - 28 000, and 8000 - 12 000. The protein with molecular weight 20 000 - 28 000 and pI 7.3-7.7 was purified 4716-fold. The cytosolic proteins were stable at 85 degrees C for 15 min and were inactivated by proteases. They did not reveal any intrinsic phosphatidate phosphohydrolase or diacylglycerol acyltransferase activity, but led to enhanced conversion of phosphatidate to diacylglycerol and triacylglycerol.
Subject(s)
Cytosol/analysis , Liver/analysis , Proteins/isolation & purification , Triglycerides/biosynthesis , Adipose Tissue/enzymology , Animals , Chromatography, DEAE-Cellulose , Electrophoresis, Disc , Isoelectric Focusing , Male , Microsomes/enzymology , Molecular Weight , Rats , Rats, Inbred StrainsSubject(s)
Acyltransferases/metabolism , Adipose Tissue/enzymology , Insulin/pharmacology , Microsomes/enzymology , Phosphatidate Phosphatase/metabolism , Phosphoric Monoester Hydrolases/metabolism , Animals , Cells, Cultured , Diglycerides , Male , Rats , Stimulation, Chemical , Triglycerides/biosynthesisABSTRACT
When propionyl-CoA was substituted for either acetyl-CoA or butyryl-CoA in the presence of [14C]malonyl-CoA and NADPH, the pure human liver fatty acids synthetase complex synthesized only straight-chain, saturated, 15- and 17-carbon radioactive fatty acids. At optimal concentrations, propionyl-CoA was a better primer of fatty acid synthesis than acetyl-CoA. Methylmalonyl-CoA inhibited the synthetase competitively with respect to malonyl-CoA. The Ki was calculated to be 8.4 muM. These findings provide an in vitro model and offer a direct explanation at the molecular level for some of the abnormal manifestations observed in diseases characterized by increased cellular concentrations of propionyl-CoA and methylmalonyl-CoA.
