Examples of mycolic acids, a class of mono- and dicyclopropane fatty acids found in the cell wall of the bacterium Mycobacterium tuberculosis

Cyclopropane fatty acids (CPA) are a subgroup of fatty acids that contain a cyclopropane group.[1] Although they are usually rare, the seed oil from lychee contains nearly 40% CPAs in the form of triglycerides.[2]


Biosynthesis

CPAs are derived from unsaturated fatty acids by cyclopropanation. The methylene donor is a methyl group on S-adenosylmethionine (SAM). The conversion is catalyzed by cyclopropane-fatty-acyl-phospholipid synthase.[3] The mechanism is proposed to involve transfer of a CH3+ group from SAM to the alkene, followed by deprotonation of the newly attached methyl group and ring closure.[4]

Cyclopropene fatty acids

malvalic acid, a cyclopropene fatty acid

Cyclopropene fatty acids are even rarer than CPAs. The best-known examples are malvalic acid and sterculic acid. Sterculic acid as its triglyceride is present in sterculia oils and at low levels in the seed oil of species of Malvaceae[lower-alpha 1] (~12%), cottonseed oil (~1%), and in the seeds of the tree Sterculia foetida (~65-78%). These acids are highly reactive but the cyclopropene ring is destroyed during refining and hydrogenation of the oils. They have attracted interest because they reduce levels of the enzyme stearoyl-CoA 9-desaturase (SCD), which catalyzes the biodesaturation of stearic acid to oleic acid.[7]

At least one review indicates that CPFA are carcinogenic, co-carcinogenic, and have medical and other effects on animals;[8] according to this review, "CPFA in food is dangerous to human health".

Notes

  1. ↑ A number of species in several genera of the Malvaceae family are known as 'Kapok trees'. For example: Ceiba pentandra, Bombax ceiba and B. costatum are all widely and ambiguously called "the kapok".[5][6]

References

  1. ↑ "Natural alicyclic fatty acids, cyclopropane, cyclopropene, cyclopentene - structure, composition, analysis, biosynthesis". Archived from the original on 2014-12-17. Retrieved 2015-02-02.
  2. ↑ Gaydou, E. M.; Ralaimanarivo, A.; Bianchini, J. P. "Cyclopropanoic Fatty-Acids of Litchi (Litchi-Chinensis) Seed Oil - a Reinvestigation" J. Agr. Food Chem. 1993, vol. 41, pp. 886-890. doi:10.1021/jf00030a009
  3. ↑ Grogan DW, Cronan JE Jr: Cyclopropane ring formation in membrane lipids of bacteria" Microbiol Mol Biol Rev 1997, vol. 61, pp. 429-441. http://mmbr.asm.org/content/61/4/429.full.pdf+html
  4. ↑ Ludger A. Wessjohann and Wolfgang Brandt, Thies Thiemann "Biosynthesis and Metabolism of Cyclopropane Rings in Natural Compounds" Chem. Rev., 2003, volume 103, pp 1625–1648. doi:10.1021/cr0100188
  5. ↑ Bohannon, M. B.; Kleiman, R. (April 1978). "Cyclopropene fatty acids of selected seed oils from bombacaceae, malvaceae, and sterculiaceae". Lipids. 13 (4): 270–273. doi:10.1007/BF02533669. PMID 661511. S2CID 4017359.
  6. ↑ Yu, Xiao-Hong; Rawat, Richa; Shanklin, John (December 2011). "Characterization and analysis of the cotton cyclopropane fatty acid synthase family and their contribution to cyclopropane fatty acid synthesis". BMC Plant Biology. 11 (1): 97. doi:10.1186/1471-2229-11-97. PMC 3132707. PMID 21612656.
  7. ↑ Abraham, Samuel (1975). International encyclopedia of pharmacology and therapeutics: Pharmacology of lipid transport and atherosclerotic processes, Volume 1. Pergamon Press. p. 108. ISBN 9780080177625.
  8. ↑ L. O. Hanus, P. Goldshlag, V. M. Dembitsky (2008). IDENTIFICATION OF CYCLOPROPYL FATTY ACIDS IN WALNUT (JUGLANS REGIA L.) OIL. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub. 2008, 152(1):41–45.

Further reading

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