Selective transacylation of 1-O-alkylglycerophosphoethanolamine by docosahexaenoate and arachidonate in rat brain microsomes.
The mechanism involved in the enzymic acylation of 1-[3H]alkylglycero-3-phosphoethanolamine (1-[3H]alkyl-GPE) in brain microsomes was investigated in comparison with the acylation of 1-[3H]alkylglycero-3-phosphocholine (1-[3H]alkyl-GPC). Both the alkyllsophospholipids were acylated without exogenously added cofactors to similar extents. The [14C]arachidonoyl moiety of exogenously added 1-stearoyl-2-[14C]arachidonoyl-GPC was transferred to the alkyllysophospholipids and the transfer was not inhibited by exogenously added free arachidonate. These results indicated that the transferase activity was due to a transacylase that catalyzes the transfer of fatty acids between intact phospholipids. The addition of CoA increased the acylation of 1-[3H]alkyl-GPC two or three times with a high acceptor concentration, and the highest rate of acylation of 1-[3H]alkyl-GPC was observed in the presence of CoA, ATP, and Mg2+. On the other hand, the addition of such cofactors only slightly increased the acylation of 1-[3H]alkyl-GPE. HPLC analysis revealed that docosahexaenoate and arachidonate were transferred to the second position of both [3H]alkyllysophospholipids without cofactors and that other fatty acids were transferred to much lower extents. With the addition of cofactors, the acylation of 1-[3H]alkyl-GPC by both docosahexaenoate and arachidonate increased 1.5-2 times, and high amounts of palmitate, oleate, and linoleate were newly transferred. High amounts of oleate were also transferred to 1-[3H]alkyl-GPE in the presence of cofactors but the acylation by both docosahexaenoate and arachidonate scarcely increased on the addition of these cofactors.(ABSTRACT TRUNCATED AT 250 WORDS)
D000215:Acylation; D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D016718:Arachidonic Acid; D001095:Arachidonic Acids / Q000378:metabolism*; D001921:Brain / Q000201:enzymology / Q000378:metabolism* / Q000648:ultrastructure*; D004281:Docosahexaenoic Acids; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D008297:Male; D008861:Microsomes / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D001095:Arachidonic Acids; D005231:Fatty Acids, Unsaturated; D010714:Phosphatidylethanolamines; D004281:Docosahexaenoic Acids; D016718:Arachidonic Acid; D000217:Acyltransferases