This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: 1-alkenes biosynthesis
|Superclasses:||Biosynthesis → Carbohydrates Biosynthesis → Olefins Biosynthesis → Alkenes Biosynthesis|
Organisms produce hydrocarbons of different types by different mechanisms. Several mechanisms have been described for the production of hydrocarbons from fatty acids or their intermediates, including synthesis of alkanes from fatty aldehydes by decarbonylation (see alkane biosynthesis I and alkane biosynthesis II), synthesis of long-chain olefins by head-to head condensation of fatty acids (see for example hentriaconta-3,6,9,12,15,19,22,25,28-nonaene biosynthesis), and production of alkenes from fatty acids by decarboxylation (see terminal olefins biosynthesis I and terminal olefins biosynthesis II).
1-Alkenes are acyclic hydrocarbons with a single carbon-carbon double bond at the very end of the molecule. Terminal olefins are similar, but may contain additional double bonds throughout the molecule. They are natural products that have important industrial applications as both fuels and chemicals. 1-Alkenes have been reported to occur in both prokaryotes eukaryotes, and are produced by several mechanisms. One such mechanism is the decarbonylation of unsaturated fatty aldehydes [Winters69, Tornabene82, Cheesbrough88, Ladygina06]. However, in some cases the alkenes are synthesized by decarboxylation of free fatty acids. Examples are 1-pentadecene in beetles of the genus Tribolium
About This Pathway
This pathway describes the production of terminal olefins by decarboxylation of fatty acids. The process has been described in Carthamus tinctorius (safflower) [Gorgen89, Ney87], and in Gram-positive bacteria of the Jeotgalicoccus genus.
Germinating safflower seedlings contain several 1-alkenes and terminal olefins, including 1-pentadecene, 1-heptadecene, 1E,8Z-heptadecadiene, 1E,8Z,11Z-heptadecatriene and 1E,8Z,11Z,14Z-heptadecatetraene, which are derived from palmitate, stearate, oleate, linoleate and α-linolenate, respectively [Binder75, Ney87]. Analysis of several Jeotgalicoccus strains showed the presence of several 1-alkenes and terminal olefins, including 1-heneicosene, 19-methyl-1-eicosene, 18-methyl-1-nonadecene, 17-methyl-1-nonadecene, 1-nonadecene, 17-methyl-1-octadecene, 16-methyl-1-heptadecene and 15-methyl-1-heptadecene [Rude11].
Cell-free lysates of Jeotgalicoccus sp. ATCC 8456 converted arachidate and stearate exclusively to 1-nonadecene and 1-heptadecene, respectively, while in vivo bioconversion of C16 and C18 fatty acids was primarily to C19 terminal olefins, suggesting that shorter chain length fatty acids may be elongated prior to decarboxylation in vivo.
The enzyme catalyzing the conversion in Jeotgalicoccus sp. ATCC 8456 is a P450 enzyme that uses hydrogen peroxide as its main source of electrons. In addition to decarboxylation, the enzyme also functions as a hydroxylase, forming minor amounts of hydroxy fatty acids [Rude11].
A mechanism that explains how the enzyme can catalyze both hydroxylation and decarboxylation of its substrates has been proposed [Rude11]. According to the model, the iron center of the P450 enzyme is oxidized by hydrogen peroxide to the high-energy oxo-ferryl heme via the hydrogen peroxide shunt. The iron then abstracts a hydrogen atom from either the α or β position of the free fatty acid, giving rise to a carbon radical on the substrate. At this point two different reactions could take place. If the oxygen rebounds, it results in hydroxylation at the α or β position forming a hydroxy fatty acid. Alternatively, an additional proton can be abstracted from the β-position, forming water and a carbocation, which can readily decarboxylate to form the terminal olefin [Rude11].
Cheesbrough88: Cheesbrough TM, Kolattukudy PE (1988). "Microsomal preparation from an animal tissue catalyzes release of carbon monoxide from a fatty aldehyde to generate an alkane." J Biol Chem 263(6);2738-43. PMID: 3343228
Goergen90: Goergen, G., Froesl, C., Boland, W., Dettner, K. (1990). "Biosynthesis of 1-alkenes in the defensive secretions of Tribolium confusum (Tenebrionidae); sterochemical implications." Experientia 46:700-704.
Gorgen89: Gorgen G, Boland W (1989). "Biosynthesis of 1-alkenes in higher plants: stereochemical implications. A model study with Carthamus tinctorius (Asteraceae)." Eur J Biochem 185(2);237-42. PMID: 2583180
Rude11: Rude MA, Baron TS, Brubaker S, Alibhai M, Del Cardayre SB, Schirmer A (2011). "Terminal olefin (1-alkene) biosynthesis by a novel p450 fatty acid decarboxylase from Jeotgalicoccus species." Appl Environ Microbiol 77(5);1718-27. PMID: 21216900
Villaverde07: Villaverde, L. M., Juarez, M. P., Mijailovsky S. (2007). "Detection of Tribolium castaneum (Herbst) volatile defensive secretions by solid phase microextraction-capillary gas chromatography (SPME-CGC)." J. Stored Prod. Res. 43:540-545.
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