title: Calcium-dependent incorporation of choline into phosphatidylcholine (PC) by base-exchange in rat brain membranes occurs preferentially with phospholipid substrates containing docosahexaenoic acid (22:6(n-3)).
abstract: The fatty acid composition of phosphatidylcholine (PC) formed by base-exchange was examined in rat brain membranes in vitro. The free choline incorporated into subspecies of PC by this phospholipase-D type activity can be distinguished from that which might enter indirectly via the last enzyme of the de novo pathway for phospholipid biosynthesis, cholinephosphotransferase, by its ionic requirements. Choline base-exchange in lysed synaptosomes is optimal when assayed at extracellular (mM) calcium concentrations and is blocked by magnesium. As much as 40% of the choline incorporated by base-exchange into rat brain membranes was recovered in subspecies of PC, representing no more than 10% of the total PC pool, which contained docosahexaenoic acid (22:6(n-3)). Docosahexaenoic acid is enriched in electrically-excitable membranes and its content in phospholipids of rat and human brain change during early development and increase with age.
authors.affiliation: Department of Brain and Cognitive Sciences E25-604, Massachusetts Institute of Technology, Cambridge.
authors.forename: P G
authors.initials: PG
authors.lastname: Holbrook
authors.forename: R J
authors.initials: RJ
authors.lastname: Wurtman
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D001923:Brain Chemistry; D002118:Calcium / Q000494:pharmacology*; D002462:Cell Membrane / Q000378:metabolism; D002794:Choline / Q000378:metabolism*; D002798:Diacylglycerol Cholinephosphotransferase / Q000378:metabolism; D004281:Docosahexaenoic Acids / Q000032:analysis* / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism; D010743:Phospholipids / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism
chemical_list: D010713:Phosphatidylcholines; D010743:Phospholipids; D004281:Docosahexaenoic Acids; D002798:Diacylglycerol Cholinephosphotransferase; D010739:Phospholipase D; D008274:Magnesium; D002794:Choline; D002118:Calcium