Structural importance of the cis-5 ethylenic bond in the endogenous desaturation product of dietary elaidic acid, cis-5,trans-9 18:2 acid, for the acylation of rat mitochondria phosphatidylinositol.
When rats were fed elaidic (trans-9 18:1) acid at a high load in diets that were otherwise marginally or almost completely deficient in linoleic (cis-9,cis-12 18:2) acid, elaidic acid was desaturated to cis-5,trans-9 18:2 acid. This polymethylene-interrupted acid was then incorporated into most phospholipids from rat mitochondria, cardiolipin being an exception. Its level of esterification in phospholipids followed the increasing order: phosphatidylethanolamine < phosphatidylcholine < phosphatidylinositol (PI). The content of cis-5,trans-9 18:2 acid decreased in organs in the order liver > kidney > heart. The levels of cis-5,trans-9 18:2 acid increased in mitochondria phospholipids as the level of linoleic acid was lowered in the diet. In liver mitochondria PI, it reached 16% of total fatty acids. After hydrolysis of liver mitochondria PI with Naja naja phospholipase A2, we observed that elaidic acid was essentially esterified to position 1 at the expense of saturated acids, whereas cis-5,trans-9 18:2 acid was exclusively esterified to position 2, along with 20:3n-9 and 20:4n-6 acids. As a consequence, the sums of saturated and trans-9 18:1 acids on the one hand, and of 20:3n-9, 20:4n-6, and cis-5,trans-9 18:2 acids on the other hand, remained fairly constant in liver mitochondria PI (ca. 55 and 30%, respectively). Because trans-9 18:1 and cis-5,trans-9 18:2 acids differ only by the cis-5 ethylenic bond, which is also present in 20:3n-9 and 20:4n-6 acids, this distribution pattern indicates that the cis-5 double bond, rather than any other ethylenic bond, may be of major structural importance for channeling fatty acids to position 2 of PI.
I.S.T.A.B., Laboratoire de Lipochimie Alimentaire, Université Bordeaux 1, Talence, France.
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D000215:Acylation; D000818:Animals; D002308:Cardiolipins / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D004951:Esterification; D005030:Ethylenes / Q000737:chemistry*; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D007668:Kidney / Q000648:ultrastructure; D019787:Linoleic Acid; D008041:Linoleic Acids / Q000008:administration & dosage; D008297:Male; D008928:Mitochondria / Q000737:chemistry* / Q000378:metabolism; D008929:Mitochondria, Heart / Q000737:chemistry / Q000378:metabolism; D008930:Mitochondria, Liver / Q000737:chemistry / Q000378:metabolism; D019301:Oleic Acid; D009829:Oleic Acids / Q000008:administration & dosage / Q000737:chemistry* / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D010716:Phosphatidylinositols / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D054467:Phospholipases A2; D051381:Rats; D017208:Rats, Wistar
D002308:Cardiolipins; D004041:Dietary Fats; D005030:Ethylenes; D008041:Linoleic Acids; D009829:Oleic Acids; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010716:Phosphatidylinositols; D019301:Oleic Acid; C011459:elaidic acid; C036216:ethylene; D019787:Linoleic Acid; D044943:Fatty Acid Desaturases; D010741:Phospholipases A; D054467:Phospholipases A2