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: head-to-head hydrocarbon biosynthesis
|Superclasses:||Biosynthesis → Carbohydrates Biosynthesis → Olefins Biosynthesis|
Some taxa known to possess this pathway include : Shewanella oneidensis MR-1
Expected Taxonomic Range: Bacteria
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 (this pathway), and production of alkenes from fatty acids by decarboxylation (see terminal olefins biosynthesis I and terminal olefins biosynthesis II).
About This Pathway
Certain microbes make olefinic long-chain hydrocarbons, generally C25 to C33, that contain a double bond near the middle of the chain. This class of compounds has been described both in Gram-positive bacteria such as Micrococcus luteus [Tornabene67, Tornabene67a] and Arthrobacter aurescens [Frias09], and in Gram-negative bacteria such as Stenotrophomonas maltophilia [Suen88]. One such compound, hentriaconta-3,6,9,12,15,19,22,25,28-nonaene (C31:9), has been reported from multiple members of the Shewanella genus [Nichols95, Tamaoka98, Sukovich10].
This class of hydrocarbons have been shown by carbon-14 labeling studies to derive from fatty acids [Albro69]. The process by which these olefins are synthesized, which was described in 1929 [Channon29], is known as head-to-head hydrocarbon biosynthesis and involves the coupling of the head (C1) and the α-carbon (C2) of two fatty acids in a reaction that involves decarboxylation of one of the fatty acid carboxyl groups [Albro69a, Albro69b].
A set of 4 Stenotrophomonas maltophilia genes involved in the pathway has been reported in patent applications filed by researchers from the LS9 company [Friedman10], and was subsequently studied in Micrococcus luteus [Beller10] and Shewanella oneidensis MR-1 [Sukovich10].
The key reaction in the pathway, the condensation of two fatty acyl-CoA molecules, is catalyzed by the OleA enzyme. The enzyme from Shewanella oneidensis MR-1 is highly specific, and produces only hentriaconta-3,6,9,12,15,19,22,25,28-nonaene [Sukovich10], while that from Stenotrophomonas maltophilia produces a much wider range of products with chain lengths of C26 to C30 [Suen88].
While the major products of the enzyme are olefins, the enzyme also produces ketones as minor products. The authors speculate that the enzyme can catalyze both decarboxilative and nondecarboxylative acyl group condensations. The nondecarboxylative condensation produces a 3-oxo acid intermediate that will decarboxylate spontaneously into a ketone [Sukovich10].
Another study of the pathway, which was conducted with Micrococcus luteus NCTC 2665 proteins, concluded that the pathway is somewhat different, and that the substrates for OleA are one fatty acyl-CoA and one β-ketoacyl-CoA, since purified OleA protein incubated with a fatty acyl-CoA substrate alone could not catalyze the reaction without addition of Escherichia coli cell lysate. The authors speculate that additional enzymes in the lysate are necessary for conversion of some of the substrate to a β-ketoacyl-CoA form [Beller10].
Albro69: Albro PW, Dittmer JC (1969). "The biochemistry of long-chain, nonisoprenoid hydrocarbonss. II. The incorporation of acetate and the aliphatic chains of isoleucine and valine into fatty acids and hydrocarbon by Sarcina lutea in vivo." Biochemistry 8(3);953-9. PMID: 5781029
Albro69a: Albro PW, Dittmer JC (1969). "The biochemistry of long-chain, nonisoprenoid hydrocarbons. 3. The metabolic relationship of long-chain fatty acids and hydrocarbons and other aspects of hydrocarbon metabolism in Sarcina lutea." Biochemistry 8(5);1913-8. PMID: 5785213
Albro69b: Albro PW, Dittmer JC (1969). "The biochemistry of long-chain, nonisoprenoid hydrocarbons. IV. Characteristics of synthesis by a cell-free preparation of Sarcina lutea." Biochemistry 8(8);3317-24. PMID: 4390164
Suen88: Suen, Y., Holzer, G.U., Hubbard, J.S., Tornabene, T.G. (1988). "Biosynthesis of acyclic methyl branched poly-unsaturated hydrocarbons in Pseudomonas maltophilia." J. Ind. Microbiol. 2:337-348.
Sukovich10: Sukovich DJ, Seffernick JL, Richman JE, Hunt KA, Gralnick JA, Wackett LP (2010). "Structure, function, and insights into the biosynthesis of a head-to-head hydrocarbon in Shewanella oneidensis strain MR-1." Appl Environ Microbiol 76(12);3842-9. PMID: 20418444
Tamaoka98: Tamaoka, J, Yanagibayashi, M., Kato, C., Horikoshi, K. (1998). "polyunsaturated hydrocarbon hentriacontanonaene (C31H46) from a deep-sea bacterium strain DSS12." Atlantic Canada Society for Microbial Ecology and International Committee on Microbial Ecology (eds) Program & Abstracts. Eighth international symposium on microbial ecology, Halifax, p 319.
Tornabene67a: Tornabene TG, Gelpi E, Oro J (1967). "Identification of fatty acids and aliphatic hydrocarbons in Sarcina lutea by gas chromatography and combined gas chromatography-mass spectrometry." J Bacteriol 94(2);333-43. PMID: 6039356
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
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