title: Differential methylation patterns in molecular species of phosphatidylethanolamine derivatives in rat liver membranes.
abstract: The appearance of individual molecular species of phospholipids in the complete sequence of the transmethylation of phosphatidylethanolamine (PE) was examined in rat liver microsomes incubated with S-adenosyl-L-[methyl-14C]methionine. Reverse-phase HPLC analysis of phosphatidylcholine (PC), phosphatidyl-N,N-dimethylethanolamine (dimethyl-PE), or phosphatidyl-N-monomethylethanolamine (monomethyl-PE) showed that radioactivity was present in the same six principal molecules; a first group is constituted by 16:0/22:6, 16:0/20:4 and 16:0/18:2 and a second one by the homologous molecules with 18:0 instead of 16:0 at the sn-1 position of glycerol. In PC, 16:0/22:6 (23% of total radioactivity) was preponderant, and 18:0/20:4 was the lowest. The ratios cpm in PC/nmol in PE were in the order: 16:0/22:6 greater than 16:0/18:2 greater than 16:0/20:4 followed by the corresponding 18:0 molecules. On the other hand, in intermediate phospholipids, incorporation of methyl groups was most marked in 18:0/20:4 (24-27% of total). 16:0/22:6 and 16:0/18:2 were low in comparison to their relative values in PC. The ratio (18:0/20:4)/(16:0/22:6) was 4.5-5.6-times higher in monomethyl-PE and dimethyl-PE than in PC. These differences were found consistently, regardless of incubation time of microsomes (2.5-60 min) and of S-adenosyl-L-methionine (AdoMet) concentration (3 or 100 microM). In liver membranes, it would therefore seem that there is a different selectivity in methyl group transfer, depending upon whether the first two steps or the third step of the reaction are considered. Side reactions, such as deacylation/reacylation, are unlikely to account for this difference, which could rather be related to the enzyme itself.
authors.affiliation: Laboratoire de Biochimie, U.R.A. 217 du C.N.R.S., Faculté de Médecine Saint-Antoine, Paris, France.
authors.forename: F
authors.initials: F
authors.lastname: Audubert
authors.forename: M
authors.initials: M
authors.lastname: Breton
authors.forename: O
authors.initials: O
authors.lastname: Colard
authors.forename: G
authors.initials: G
authors.lastname: Bereziat
mesh_terms: D000818:Animals; D002849:Chromatography, Gas; D002851:Chromatography, High Pressure Liquid; D005227:Fatty Acids / Q000032:analysis; D005260:Female; D007425:Intracellular Membranes / Q000378:metabolism; D008745:Methylation; D008862:Microsomes, Liver / Q000378:metabolism*; D015394:Molecular Structure; D010713:Phosphatidylcholines / Q000032:analysis / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000032:analysis / Q000378:metabolism*; D051381:Rats; D012436:S-Adenosylmethionine / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D012436:S-Adenosylmethionine