Conversion of 18:3 delta 9cis, 12cis, 15trans in rat liver microsomes.
Several years ago, it was established that the delta 15 trans isomer of alpha-linolenic acid is converted in vivo into fatty acids containing 20 and 22 carbons (geometrical isomers of eicosapentaenoic and docosahexaenoic acids). The present study focused on the in vitro delta 6 desaturation, the first step of the biosynthesis of the n-3 long-chain polyunsaturated fatty acids from 18:3n-3. For that purpose, rat liver microsomes were prepared and incubated with radiolabeled 18:3 delta 9cis,12cis,15cis (18:3c,c,c) or 18:3 delta 9cis, 12cis, 15trans (18:3c,c,t) under desaturation conditions. The data show that 18:3c,c,t is converted at a lower rate compared with alpha-linolenic acid. The product of conversion of 18:3c,c,t may be 18:4 delta 6cis, 9cis, 12cis, 15trans resulting from a delta 6 desaturation of the trans substrate. Moreover, the conversion of radiolabeled 18:3c,c,t was strongly decreased by the presence of 18:3c,c,c (up to 48%) while the 18:3c,c,t only slightly decreased the conversion of radiolabeled 18:3c,c,c. Thus, the desaturation enzyme presented a higher affinity for the native all-cis n-3 substrate.
Chardigny
J M
JM
INRA, Unité de Nutrition Lipidique, Dijon, France. chardign@dijon-inra.fr
Blond
J P
JP
Bretillon
L
L
Mager
E
E
Poullain
D
D
Martine
L
L
Vatèle
J M
JM
Noĕl
J P
JP
Sébédio
J L
JL
D000818:Animals; D002849:Chromatography, Gas; D018752:Diet, Fat-Restricted; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D007536:Isomerism; D008042:Linolenic Acids / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar
D005231:Fatty Acids, Unsaturated; D008042:Linolenic Acids