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Phosphatidylcholine molecular species involved in Γ ‐linolenic acid biosynthesis in microsomes from borage seeds
Author(s) -
GalleLe Bastard A. M.,
Demandre C.,
Oursel A.,
Joseph M.,
Mazliak P.,
Kader J. C.
Publication year - 2000
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1034/j.1399-3054.2000.108002118.x
Subject(s) - microsome , phosphatidylcholine , biochemistry , biosynthesis , linolenic acid , microsoma , fatty acid , biology , acylation , glycerol , diglyceride , stereochemistry , chemistry , phospholipid , linoleic acid , in vitro , enzyme , membrane , catalysis
Boraginaceae seeds are particularly rich in Γ ‐linolenic acid (6,9,12‐octadecatrienoic acid, Γ ‐18:3). In microsomes, the analysis of phosphatidylcholine (PC) molecular species by HPLC led to identification of 15 different molecular species; among them 4 contained Γ ‐18:3, mostly at position 2 of sn ‐glycerol. Time courses of acylation and desaturation in PC molecular species were examined when [ 14 C]oleoyl‐CoA or [ 14 C]linoleoyl‐CoA was provided as substrates to isolated microsomes. With [ 14 C]oleoyl‐CoA or [ 14 C]linoleoyl‐CoA and in the absence of NADH, 3 main labelled PC molecular species were found: 18:2/[ 14 C]18:1, 16:0/[ 14 C]18:1 and 18:1/[ 14 C]18:1. When NADH was present in the incubation medium, the fatty acids were progressively desaturated by the Δ12‐ and Δ6‐desaturases successively (with [ 14 C]oleoyl‐CoA as precursor) or by the Δ6‐desaturase alone (with [ 14 C]linoleoyl‐CoA as precursor). In both types of experiments, 7 final desaturation products in microsomes were evidenced; among them, 3 contained radioactive Γ ‐18:3, i.e . 18:2/[ 14 C] Γ ‐18:3, 18:1/[ 14 C] Γ ‐18:3 and 16:0/[ 14 C] Γ ‐18:3. While the Δ12‐desaturase had no specificity for position on the glycerol backbone, labelled Γ ‐linolenic acid was recovered exclusively in the sn ‐2 position.