title: Phospholipid synthesis in isolated fat cells. Studies of microsomal diacylglycerol cholinephosphotransferase and diacylglycerol ethanolaminephosphotransferase activities.
abstract: Diacylglycerol cholinephosphotransferase (EC 2.7.8.2) and diacylglycerol ethanolaminephosphotransferase (EC 2.7.8.1) activities were investigated in microsomes from isolated rat fat cells. Assays based on the conversion of CDP-[14C]choline of CDP-[14C]ethanolamine to phosphatidylcholine or phosphatidylethanolamine utilized ethanol-dispersed diacylglycerols and 1 to 5 microng of protein. Cholinephosphotransferase and ethanolaminephosphotransferase activities had similar dependences on MgCl2 and pH, and were inhibited similarly by CaCl2, organic solvents, Triton X-100, Tween 20, and dithiothreitol. Ethylene glycol bis(beta-amino-ethyl ether)-N,N,N',N'-tetraacetic acid stimulated both activities similarly. With 1,2-dioleoyl-sn-glycerol, the cholinephosphotransferase activity had an apparent Km for CDP-choline of 23.9 micronM and a V max of 8.54 nmol/min/mg. CDP-ethanolamine and CDP were competitive inhibitors of the cholinephosphotransferase activity (apparent Kl values of 227 micronM and 360 micronM, respectively). With 1,2-dioleoyl-sn-glycerol, the ethanolaminephosphotransferase activity had an apparent Km of 18.3 micronM for CDP-ethanolamine and a V max of 1.14 nmol/min/mg. CDP-choline appeared to be a noncompetitive inhibitor of the ethanolaminephosphotransferase activity (apparent Kl of 1620 micronM). Inhibition of the ethanolaminephosphotransferase activity by CDP appeared to be of a mixed type. The dependences on diacylglycerols containing fatty acids 6 to 18 carbons in length were investigated...
mesh_terms: D000273:Adipose Tissue / Q000166:cytology / Q000201:enzymology*; D000818:Animals; D001667:Binding, Competitive; D003566:Cytidine Diphosphate Choline / Q000494:pharmacology; D002798:Diacylglycerol Cholinephosphotransferase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004075:Diglycerides / Q000494:pharmacology; D004355:Drug Stability; D004983:Ethanolamines / Q000494:pharmacology; D005260:Female; D006358:Hot Temperature; D007700:Kinetics; D008861:Microsomes / Q000201:enzymology*; D010743:Phospholipids / Q000096:biosynthesis*; D010770:Phosphotransferases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship
chemical_list: D004075:Diglycerides; D004983:Ethanolamines; D010743:Phospholipids; D003566:Cytidine Diphosphate Choline; D010770:Phosphotransferases; D002798:Diacylglycerol Cholinephosphotransferase