In vivo and in vitro evidence for biochemical coupling of reactions catalyzed by lysophosphatidylcholine acyltransferase and diacylglycerol acyltransferase

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DOIResolve DOI: http://doi.org/10.1074/jbc.M115.654798
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TypeArticle
Journal titleJournal of Biological Chemistry
ISSN0021-9258
Volume290
Issue29
Pages1806818078; # of pages: 11
SubjectFatty acids; Flax; Glycerol; Linen; Lipids; Oilseeds; Phospholipids; Seed; embryo
AbstractSeed oils of flax (Linum usitatissimum L.) and many other plant species contain substantial amounts of polyunsaturated fatty acids (PUFAs). Phosphatidylcholine (PC) is the major site for PUFA synthesis. The exact mechanisms of how these PUFAs are channeled from PC into triacylglycerol (TAG) needs to be further explored. By using in vivo and in vitro approaches, we demonstrated that the PC deacylation reaction catalyzed by the reverse action of acyl-CoA:lysophosphatidylcholine acyltransferase (LPCAT) can transfer PUFAs on PC directly into the acyl-CoA pool, making these PUFAs available for the diacylglycerol acyltransferase (DGAT)-catalyzed reaction for TAG production. Two types of yeast mutants were generated for in vivo and in vitro experiments, respectively. Both mutants provide a null background with no endogenous TAG forming capacity and an extremely low LPCAT activity. In vivo experiments showed that co-expressing flax DGAT1-1 and LPCAT1 in the yeast quintuple mutant significantly increased 18-carbon PUFAs in TAG with a concomitant decrease of 18-carbon PUFAs in phospholipid. We further showed that after incubation of sn-2-[14C]acyl-PC, formation of [14C]TAG was only possible with yeast microsomes containing both LPCAT1 and DGAT1-1. Moreover, the specific activity of overall LPCAT1 and DGAT1-1 coupling process exhibited a preference for transferring 14C-labeled linoleoyl or linolenoyl than oleoyl moieties from the sn-2 position of PC to TAG. Together, our data support the hypothesis of biochemical coupling of the LPCAT1-catalyzed reverse reaction with the DGAT1-1-catalyzed reaction for incorporating PUFAs into TAG. This process represents a potential route for enriching TAG in PUFA content during seed development in flax.
Publication date
LanguageEnglish
AffiliationAquatic and Crop Resource Development; National Research Council Canada
Peer reviewedYes
NPARC number21276931
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Record identifiera255a83a-3582-401e-964b-b243f20d2a10
Record created2015-11-10
Record modified2016-05-09
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