title: Evidence for the presence of CDP-ethanolamine: 1,2-diacyl-sn-glycerol ethanolaminephosphotransferase in rat central nervous system myelin.
abstract: Highly purified rat brain myelin isolated by two different procedures showed appreciable activity for CDP-ethanolamine: 1,2-diacyl-sn-glycerol ethanolaminephosphotransferase (EC 2.7.8.1). Specific activity was close to that of total homogenate and approximately 12-16% that of brain microsomes. Three other lipid-synthesizing enzymes, cerebroside sulfotransferase, lactosylceramide sialyltransferase, and serine phospholipid exchange enzyme, were found to have less than 0.5% the specific activity in myelin compared with microsomes. Washing the myelin with buffered salt or taurocholate did not remove the phosphotransferase, but activity was lost from both myelin and microsomes by treatment with Triton X-100. It resembled the microsomal enzyme in having a pH optimum of 8.5 and a requirement for Mn2+ and detergent, but differed in showing no enhancement with EGTA. The diolein Km was similar for the two membranes (2.5-4 x 10(-4) M), but the CDP-ethanolamine Km was lower for myelin (3-4 x 10(-5) M) than  for microsomes (11 - 13 x 10(-5 M). Evidence is reviewed that this enzyme is able to utilize substrate from the axon in situ.
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D003902:Detergents / Q000494:pharmacology; D004982:Ethanolaminephosphotransferase / Q000032:analysis*; D008861:Microsomes / Q000201:enzymology; D009186:Myelin Sheath / Q000201:enzymology*; D010770:Phosphotransferases / Q000032:analysis*; D051381:Rats; D012492:Salts / Q000494:pharmacology
chemical_list: D003902:Detergents; D012492:Salts; D010770:Phosphotransferases; D004982:Ethanolaminephosphotransferase