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 → Auxins Biosynthesis|
|Degradation/Utilization/Assimilation → Amino Acids Degradation → Proteinogenic Amino Acids Degradation → L-tryptophan Degradation|
Some taxa known to possess this pathway include : Agrobacterium tumefaciens , Azospirillum brasilense , Azospirillum lipoferum , Azotobacter vinelandii , Bradyrhizobium japonicum , Burkholderia pyrrocinia , Enterobacter cloacae , Escherichia coli K4 , Pantoea agglomerans , Pseudomonas chlororaphis chlororaphis , Pseudomonas fluorescens , Sinorhizobium meliloti Rm2011 , Sulfolobus tokodaii 7
The metabolism of tryptophan to indole-3-acetate (indole acetic acid, IAA) via indole-3-pyruvate and indole-3-acetaldehyde has been documented in several nonpathogenic plant-associated bacteria, such as Bradyrhizobium japonicum [Kaneshiro83], Rhizobium leguminosarum [BadenochJones82] and Azotobacter vinlandii [GarciaTabares87], as well as the tumorigenic Agrobacterium tumefaciens [Kaper58], Pseudomonas savastanoi [Kuo73], and Pantoea agglomerans pv. gypsophilae [Manulis91]. In addition, a recent report described the presence of this pathway in the archaeon Sulfolobus sp. strain 7, a hyperthermophilic organism which is not associated with plants.
Initially it was difficult to prove the existence of this pathway, due to low rate of IAA synthesis, and the fact that indole-3-pyruvate is converted to IAA non-enzymatically. However, work done with the organism Enterobacter cloacae, which produces IAA in a higher rate, enabled the elucidation of the pathway and the identification of its components.
The key enzyme of this pathway is indole-3-pyruvate carboxylase (IPDC), as the two other enzymes which participate in this pathway are usually present in most bacteria, including those that cannot produce IAA. Upon expression of the E. cloacae IPDC enzyme in the heterologous hosts Escherichia coli, Enterobacter aerogenes, Pantoea agglomerans, Pseudomonas putida, Pseudomonas fluorescens, and Agrobacterium tumefaciens, all of these organisms were able to convert L-tryptophan to IAA [Koga91, Koga95]. Furthermore, experiments have shown that IPDC is solely responsible for the regulation of this pathway, and that the first enzyme in the pathway, L-tryptophan aminotransferase, operates very close to equilibrium [Koga94].
There has been a report that in certain organisms (Burkholderia pyrrocinia, formerly known as Pseudomonas pyrrocinia, and Pseudomonas chlororaphis, formerly known as Pseudomonas aureofaciens) the pathway continues further: IAA is metabolized to indole-3-caboxaldehyde, which is converted by dehydrogenation to indole-3-carboxylate. The later undergoes spontaneous decarboxylation into indole [Lubbe83].
Variants: indole-3-acetate activation I , indole-3-acetate activation II , indole-3-acetate biosynthesis I , indole-3-acetate biosynthesis II , indole-3-acetate biosynthesis III (bacteria) , indole-3-acetate biosynthesis IV (bacteria) , indole-3-acetate biosynthesis V (bacteria and fungi) , L-tryptophan degradation I (via anthranilate) , L-tryptophan degradation II (via pyruvate) , L-tryptophan degradation III (eukaryotic) , L-tryptophan degradation IV (via indole-3-lactate) , L-tryptophan degradation VI (via tryptamine) , L-tryptophan degradation VIII (to tryptophol) , L-tryptophan degradation IX , L-tryptophan degradation to 2-amino-3-carboxymuconate semialdehyde , L-tryptophan degradation V (side chain pathway) , L-tryptophan degradation X (mammalian, via tryptamine) , L-tryptophan degradation XI (mammalian, via kynurenine) , L-tryptophan degradation XII (Geobacillus) , methyl indole-3-acetate interconversion
BadenochJones82: Badenoch-Jones, J., Summons, R. E., Rolfe, B. G., Parker, C. W., Letham, D. S. (1982). "Mass spectrometric identification of indole compounds produced by Rhizobium strains." Biomed. Mass Spectrom. 9:429-437.
Brandl96: Brandl MT, Lindow SE (1996). "Cloning and characterization of a locus encoding an indolepyruvate decarboxylase involved in indole-3-acetic acid synthesis in Erwinia herbicola." Appl Environ Microbiol 62(11);4121-8. PMID: 8900003
GarciaTabares87: Garcia-Tabares, F., Herraiz-Tomico, T., Amat-Guerri, F., Garcia-Bilbao, J.L. (1987). "Production of 3-IAA and 3-indolelactic acid in Azotobacter vinelandii cultures supplemented with tryptophan." Appl. Microbiol. Biotechnol. 25:502-506.
Koga92: Koga J, Adachi T, Hidaka H (1992). "Purification and characterization of indolepyruvate decarboxylase. A novel enzyme for indole-3-acetic acid biosynthesis in Enterobacter cloacae." J Biol Chem 267(22);15823-8. PMID: 1639814
Koga94: Koga J, Syono K, Ichikawa T, Adachi T (1994). "Involvement of L-tryptophan aminotransferase in indole-3-acetic acid biosynthesis in Enterobacter cloacae." Biochim Biophys Acta 1209(2);241-7. PMID: 7811697
Lubbe83: Lubbe C, van Pee KH, Salcher O, Lingens F (1983). "The metabolism of tryptophan and 7-chlorotryptophan in Pseudomonas pyrrocinia and Pseudomonas aureofaciens." Hoppe Seylers Z Physiol Chem 364(4);447-53. PMID: 6862384
Manulis91: Manulis, S., Valinski, L., Gafni, Y. (1991). "Indole-3-acetic acid biosynthetic pathways in Erwinia herbicola in relation to pathogenicity on Gypsophila paniculata." Physiol. Mol. Plant Pathol. 39:161-171.
Baca94: Baca, B. E., Soto-Urzua, L., Xochihua-Corona, Y. G., Cuervo-Garcia, A. (1994). "Characterization of two aromatic amino acid aminotransferases and production of indole-3-acetic acid in Azospirillum spp. strains." Soil Biol. Biochem. 26:57-63.
Cooney91: Cooney, T.P., Nonhebel, H.M. (1991). "Biosynthesis of indole-3-acetic acid in tomato shoots: Measurement, mass-spectral identification and incorporation of -2H from -2H2O into indole-3-acetic acid, d- and l-tryptophan, indole-3-pyruvate and tryptamine." Planta. 184 (3): 368-376.
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Schutz03: Schutz A, Sandalova T, Ricagno S, Hubner G, Konig S, Schneider G (2003). "Crystal structure of thiamindiphosphate-dependent indolepyruvate decarboxylase from Enterobacter cloacae, an enzyme involved in the biosynthesis of the plant hormone indole-3-acetic acid." Eur J Biochem 270(10);2312-21. PMID: 12752451
SotoUrzua96: Soto-Urzua L, Xochinua-Corona YG, Flores-Encarnacion M, Baca BE (1996). "Purification and properties of aromatic amino acid aminotransferases from Azospirillum brasilense UAP 14 strain." Can J Microbiol 42(3);294-8. PMID: 8868238
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Tam98: Tam YY, Normanly J (1998). "Determination of indole-3-pyruvic acid levels in Arabidopsis thaliana by gas chromatography-selected ion monitoring-mass spectrometry." J Chromatogr A 800(1);101-8. PMID: 9561757
Tao08: Tao Y, Ferrer JL, Ljung K, Pojer F, Hong F, Long JA, Li L, Moreno JE, Bowman ME, Ivans LJ, Cheng Y, Lim J, Zhao Y, Ballare CL, Sandberg G, Noel JP, Chory J (2008). "Rapid synthesis of auxin via a new tryptophan-dependent pathway is required for shade avoidance in plants." Cell 133(1);164-76. PMID: 18394996
Truelsen72: Truelsen, T.A. (1972). "Indole-3-Pyruvic Acid as an Intermediate in the Conversion of Tryptophan to Indole-3-Acetic Acid. II. Distribution of Tryptophan Transaminase Activity in Plants." Physiologia Plantarum. 28 (1): 67-70.
Urrestarazu98: Urrestarazu A, Vissers S, Iraqui I, Grenson M (1998). "Phenylalanine- and tyrosine-auxotrophic mutants of Saccharomyces cerevisiae impaired in transamination." Mol Gen Genet 257(2);230-7. PMID: 9491082
Wakagi02: Wakagi T, Fukuda E, Ogawa Y, Kino H, Matsuzawa H (2002). "A novel bifunctional molybdo-enzyme catalyzing both decarboxylation of indolepyruvate and oxidation of indoleacetaldehyde from a thermoacidophilic archaeon, Sulfolobus sp. strain 7." FEBS Lett 510(3);196-200. PMID: 11801253
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