Accepton concentration effect in the selectivity of acyl coenzyme A: U aclglycerylphosphorylcholine acyltransferase system in rat liver.
In the acylation of 1-acylglycerylphosphorylcholine (1-acyl-GPC) in rat liver, neither the specificity observed with Triton X-100 treated microsomes were consistent with the selectivity observed in vivo. This apparent discrepancy was solved as follows. 1. Crude microsomes or deoxycholate-treated microsomes had approximately the same levels of activities for oleoyl-, linoleoyl- and arachidonoyl-CoAs. Triton X-100 treated microsomes had much higher activity for arachidonate but very little activity for oleate, which was found to be the consequence of selective inactivation by Triton X-100 of oleoyl-CoA:1-acyl-GPC acyl transfer reaction. These observations favor a concept that different enzymes or different sites on a single enzyme exist in rat liver microsomes for the transfers of different acyl-CoAs. 2. Although the maximum velocities for oleoyl-CoA and arachidonoyl-CoA were approximately the same, more arachidonate was incorporated than oleate at very low concentrations of the acceptor even when both acyl-CoAs were present at saturating concentrations. Thus, higher selectivity for arachidonate (and linoleate to a lesser extent) observed with rat liver in vivo could be correlated with relatively higher affinity in this reaction for 1-acyl-GPC observed in vitro, which exerts its effect at low concentrations of the acceptor.
D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D003065:Coenzyme A / Q000378:metabolism; D003840:Deoxycholic Acid / Q000494:pharmacology; D005227:Fatty Acids / Q000378:metabolism; D008244:Lysophosphatidylcholines; D008862:Microsomes, Liver / Q000201:enzymology*; D009829:Oleic Acids / Q000378:metabolism; D011092:Polyethylene Glycols / Q000494:pharmacology; D051381:Rats; D013329:Structure-Activity Relationship
D001095:Arachidonic Acids; D005227:Fatty Acids; D008244:Lysophosphatidylcholines; D009829:Oleic Acids; D003840:Deoxycholic Acid; D011092:Polyethylene Glycols; D000217:Acyltransferases; D003065:Coenzyme A