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.
|Superclasses:||Biosynthesis → Hormones Biosynthesis → Plant Hormones Biosynthesis → Ethylene Biosynthesis|
Ethylene is known in plants, fungi and bacteria. In plants, ethylene is an important hormone that regulates plant growth and development. It is well-known as a fruit-ripening hormone and is biologically active in trace amounts. Ethylene also plays a general role as a growth inhibitor in promoting leaf and flower senescence and abscission.
All plants produce ethylene from L-methionine as described in the pathway ethylene biosynthesis I (plants). In addition, two alternative ethylene biosynthetic pathways have been reported from microorganisms. Most microorganisms produce only trace amounts of ethylene via the 2-oxo-4-methylthiobutanoate (KMBA) pathway [Nagahama92] (see ethylene biosynthesis III (microbes)). In that pathway ethylene is produced non-enzymatically by hydroxyl radicals that are produced from molecular oxygen by an NADH:Fe(III)EDTA oxidoreductase [Ince86, Fukuda89, Ogawa90]. The second microbial pathway, which is described here, is found mostly in members of the Pseudomonas syringae group. In this pathway ethylene is formed enzymatically from 2-oxoglutarate.
Being the simplest unsaturated organic molecule, ethylene is the building block for synthetic polymers including plastics such as polyethylene. Large amounts of ethylene are currently produced in a chemical process from fossil fuels. Ethylene has the highest annual global production of all synthetic organic molecules.
About This Pathway
A novel ethylene-forming enzyme that forms ethylene from 2-ketoglutarate was purified in 1989 from Penicillium digitatum IFO 9372, the green mold of citrus fruit that is known to produce large quantities of ethylene [Fukuda89a]. The substrate and cofactor specificities of the enzyme, which was named simply "ethylene-forming enzyme", were highly specific for 2-ketoglutarate and L-arginine, respectively.
An enzyme with a very similar activity, although a different amino acid sequence, has been described from the bacterium Pseudomonas savastanoi pv. phaseolicola [Goto87, Nagahama91, Nagahama91a, Fukuda92]. The enzyme is plasmid-encoded, and has been eventually detected in many strains of Pseudomonas syringae [Fukuda92a, Nagahama94]. The enzyme catalyzes a very complex reaction, or more accurately, two simultaneous reactions followed by yet a third reaction. In the main reaction 2-oxoglutarate is dioxygenated to form one molecule of ethylene and three molecules of carbon dioxide. In a second reaction both 2-oxoglutarate and L-arginine are mono-oxygenated simultaneously to yield succinate plus CO2 and Nω-hydroxy-L-arginine, respectively. The latter is further transformed in a third reaction to guanidinium and (S)-1-pyrroline-5-carboxylate. The overall reaction can be described as
The main product of the enzyme is ethylene. The purpose of the in vivo production of succinate is not clear. It has been suggested that this reaction supresses the ethylene-forming reaction via the decomposition of L-arginine.
One of the final products, (S)-1-pyrroline-5-carboxylate, can be converted to L-glutamate by EC 184.108.40.206, 1-pyrroline-5-carboxylate dehydrogenase. The glutamate that is formed can be recycled back to L-arginine via the acetyl cycle, thus feeding back into the succinate-forming reaction of the ethylene-forming enzyme.
The efe gene, which encodes the ethylene-forming enzyme, has been cloned and expressed successfully in many organisms including Escherichia coli BL21 [Dong07], Saccharomyces cerevisiae [Pirkov08], Trichoderma viride [Tao08], Synechococcus elongatus PCC 7942 [Takahama03] and in Pseudomonas putida KT2440 [Wang10d].
Fukuda89: Fukuda H, Takahashi M, Fujii T, Tazaki M, Ogawa T (1989). "An NADH:Fe(III)EDTA oxidoreductase from Cryptococcus albidus: an enzyme involved in ethylene production in vivo?." FEMS Microbiol Lett 51(1);107-11. PMID: 2792734
Fukuda89a: Fukuda, H, Kitajima, H, Fujii, T, Tazaki, M, Ogawa, T (1989). "Purification and some properties of a novel ethylene-forming enzyme produced by Penicillium digitatum." FEMS Microbiology Letters 59:1-6.
Fukuda92: Fukuda H, Ogawa T, Tazaki M, Nagahama K, Fujii T, Tanase S, Morino Y (1992). "Two reactions are simultaneously catalyzed by a single enzyme: the arginine-dependent simultaneous formation of two products, ethylene and succinate, from 2-oxoglutarate by an enzyme from Pseudomonas syringae." Biochem Biophys Res Commun 188(2);483-9. PMID: 1445291
Fukuda92a: Fukuda H, Ogawa T, Ishihara K, Fujii T, Nagahama K, Omata T, Inoue Y, Tanase S, Morino Y (1992). "Molecular cloning in Escherichia coli, expression, and nucleotide sequence of the gene for the ethylene-forming enzyme of Pseudomonas syringae pv. phaseolicola PK2." Biochem Biophys Res Commun 188(2);826-32. PMID: 1445325
Nagahama91: Nagahama, K., Ogawa, T., Fujii, T., Tazaki, M., Goto, M., Fukuda, H. (1991). "L-Arginine is essential for the formation in vitro of ethylene by an extract of Pseudomonas syringae." Journal of General Microbiology 137(7):1641-1646.
Nagahama91a: Nagahama, K., Ogawa, T., Fujii, T., Tazaki, M., Tanase, S., Morino, Y., Fukuda, H. (1991). "Purification and properties of an ethylene-forming enzyme from Pseudomonas syringae pv. Phaseolicola PK2." Journal of General Microbiology 137(10):2281-2286. PMID: 1770346
Nagahama92: Nagahama, K., Ogawa, T., Fujii, T., Fukuda, H. (1992). "Classification of ethylene-producing bacteria in terms of biosynthetic pathways to ethylene." Journal of Fermentation and Bioengineering 73(1):1-5.
Nagahama94: Nagahama K, Yoshino K, Matsuoka M, Sato M, Tanase S, Ogawa T, Fukuda H (1994). "Ethylene production by strains of the plant-pathogenic bacterium Pseudomonas syringae depends upon the presence of indigenous plasmids carrying homologous genes for the ethylene-forming enzyme." Microbiology 140 ( Pt 9);2309-13. PMID: 7952184
Ogawa90: Ogawa, T., Takahashi, M., Fujii, T., Tazaki, M., Fukuda, H. (1990). "The Role of NADH:Fe(III)EDTA Oxidoreductase in Ethylene Formation from 2-Keto-4-Methylthiobutyrate." Journal of Fermentation and Bioengineering 69(5):287-291.
Takahama03: Takahama K, Matsuoka M, Nagahama K, Ogawa T (2003). "Construction and analysis of a recombinant cyanobacterium expressing a chromosomally inserted gene for an ethylene-forming enzyme at the psbAI locus." J Biosci Bioeng 95(3);302-5. PMID: 16233410
Tao08: Tao L, Dong HJ, Chen X, Chen SF, Wang TH (2008). "Expression of ethylene-forming enzyme (EFE) of Pseudomonas syringae pv. glycinea in Trichoderma viride." Appl Microbiol Biotechnol 80(4);573-8. PMID: 18575855
Wang10d: Wang JP, Wu LX, Xu F, Lv J, Jin HJ, Chen SF (2010). "Metabolic engineering for ethylene production by inserting the ethylene-forming enzyme gene (efe) at the 16S rDNA sites of Pseudomonas putida KT2440." Bioresour Technol 101(16);6404-9. PMID: 20399645
BSUB93: "Bacillus subtilis and Other Gram-Positive Bacteria: Biochemistry, Physiology, and Molecular Genetics." (1993). Editors: Sonenshein, A.L., Hoch, J.A., Losick, R. American Society For Microbiology, Washington, DC.
Deuschle04: Deuschle K, Funck D, Forlani G, Stransky H, Biehl A, Leister D, van der Graaff E, Kunze R, Frommer WB (2004). "The role of [Delta]1-pyrroline-5-carboxylate dehydrogenase in proline degradation." Plant Cell 16(12);3413-25. PMID: 15548746
ForteMcRobbie86: Forte-McRobbie CM, Pietruszko R (1986). "Purification and characterization of human liver "high Km" aldehyde dehydrogenase and its identification as glutamic gamma-semialdehyde dehydrogenase." J Biol Chem 261(5);2154-63. PMID: 3944130
Gardan97: Gardan R, Rapoport G, Debarbouille M (1997). "Role of the transcriptional activator RocR in the arginine-degradation pathway of Bacillus subtilis." Mol Microbiol 1997;24(4);825-37. PMID: 9194709
Ju04: Ju J, Ozanick SG, Shen B, Thomas MG (2004). "Conversion of (2S)-arginine to (2S,3R)-capreomycidine by VioC and VioD from the viomycin biosynthetic pathway of Streptomyces sp. strain ATCC11861." Chembiochem 5(9);1281-5. PMID: 15368582
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