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. 1980 Oct;66(4):649–655. doi: 10.1104/pp.66.4.649

Biosynthesis of C20 and C22 Fatty Acids by Developing Seeds of Limnanthes alba

CHAIN ELONGATION AND Δ5 DESATURATION1

Michael R Pollard 1,2, Paul K Stumpf 1
PMCID: PMC440697  PMID: 16661496

Abstract

The storage triacylglycerols of meadowfoam (Limnanthes alba) seeds are composed essentially of C20 and C22 fatty acids, which contain an unusual Δ5 double bond. When [1-14C]acetate was incubated with developing seed slices, 14C-labeled fatty acids were synthesized with a distribution similar to the endogenous fatty acid profile. The major labeled product was cis-5-eicosenoate, with smaller amounts of palmitate, stearate, oleate, cis-5-octadecenoate, eicosanoate, cis-11-eicosenoate, docosanoate, cis-5-docosenoate, cis-13-docosenoate, and cis-5,cis-13-docosadienoate. The label from [14C]acetate and [14C]malonate was used preferentially for the elongation of endogenous oleate to produce cis-[14C]11-eicosenoate, cis-13-[14C]docosenoate, and cis-5,cis-13-[14C]docosadienoate and for the elongation of endogenous palmitate to produce the remaining C20 and C22 acyl species. The Δ5 desaturation of the preformed acyl chain and chain elongation of oleate and palmitate were demonstrated in vivo by incubation of the appropriate 1-14C-labeled free fatty acids. Using [1-14C]acyl-CoA thioesters as substrates, these enzyme activities were also demonstrated in vitro with a cell-free homogenate.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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