Indole-3-acetic acid biosynthesis

HULL, A.K., VU, R., CELENZA, J.L., Arabidopsis cytochrome P450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis, Proc. Natl. Acad. Sci. USA, 2000,97,2379-2384. 

Mazzola M, White FF, A mutation in the indole 3-acetic acid biosynthesis and syringomycin production. ] Bacteiio 1994 176 1374-1382. 

Indole-3-Ethanol Metabolism and Its Possible Role in the Regulation of Indole-3-Acetic Acid Biosynthesis... 

Figure 5.41 Early steps of the proposed indole acetic acid biosynthesis pathways for Ara-bidopsis. CHO, chorismate ANA, anthranilate PANA, 5-phosphoribosylanthranilate CADP, l-(o-carboxyphenylamino)-l-deoxyribulose-5-phosphate IGP, indole-3-glycerol phosphate TRP, tryptophan. Enzymes ASA, anthranilate synthetase, suhunit a ASB, anthranilate synthetase, suhunit P PAT, phosphorihosylanthranUate transferase PAI, phosphoiibosylanthrani-late isomerase IGS, indole-3-glycerol-phosphate synthase TSA, tryptophan synthase, subunit a and TSB, tryptophan synthase, suhunit p.

Figure 5.42 Proposed tryptophan-dependent indole acetic acid biosynthesis pathways for Arabidopsis. Dashed arrows indicate that neither a gene nor enzyme activity has been identified in Arabidopsis. lAM, indole-3-acetamide IPA, indole-3-pyruvic acid lAAld, indole-3-acetaldehyde lAOx, indole-3-acetaldoxime 5-lAH-L-cys,...

Figure 5.43 Proposed tryptophan-independent indole acetic acid biosynthesis pathway.

An additional insight into the importance of specific media components on production of secondary products can be gained by examining the case history of shikonin production. It had been shown that callus cultures of Lithospermum erythrorhizon could be induced to produce shikonin on Linsmaier-Skoog medium supplemented with lpM indole acetic acid (IAA) and lOpM kinetin (KIN) (52). The effects of specific nutritional components of the tissue culture medium on growth of the cell cultures and production of shikonin were also investigated i53). Fujita et al. (54,55) found that the levels of NO,, Cu+, and SO had profound effects of shikonin biosynthesis. Optimal concentrations were identified for each ion (I 8 ) as well as optimal levels of key organic components. The resultant medium supported production of shikonin at a rate approximately 13 times that obtained on previous media formulations. 

Fig. 7.6. Biosynthesis of indole acetic acid (modified from Smith, 1980 used with permission of the copyright owner, Springer-Verlag, Berlin).

Figure 6.20. Biosynthesis and catabolism of indole acetic acid...

Yu and Wang431 considered that indole-3-acetic acid exerts its stimulating effect on expansion growth by inducing the synthesis of the enzyme catalyzing the conversion of S-adenosylmethionine into ACC, a conclusion at variance with the suggestion of Vioque and coworkers432 that indoleacetic acid oxidase and its substrate (IAA) participate in the last reaction in the ethylene biosynthesis pathway, namely, the formation of ethylene from ACC. 

Nitrilase was initially discovered in plants as an enzyme involved in the biosynthesis of the plant hormone indole-3-acetic acid (IAA) [74,75], Recently, four genes of nitrilases (belonging to arylacetonitrilase) involved in the IAA biosynthesis have been cloned and characterized from Arabidopsis thaliana [76-78], After the discovery of the plant nitrilase in 1964, various nitrilases were purified and characterized [41], Nitrilases are roughly classified into three major categories according to substrate specificity (i) aromatic nitrilase, which acts on aromatic or heterocyclic nitriles (ii) aliphatic nitrilase, which acts on aliphatic nitriles (iii) arylacetonitrilase, which acts on arylacetonitriles. These three types... 

Patten, C.L., Click, B.R. Bacterial biosynthesis of indole-3-acetic acid. Can J Microbiol 1996 42 207-220. 

All these compounds are intermediates in indole-3-acetic acid (auxin) biosynthesis of plants. They have been prepared on microscale341 with reasonably high yield, high purity... 

Kobayashi, M., Suzuki, T., Fujita, T, et al. 1995. Occurrence of enzymes involved in biosynthesis of indole-3-acetic acid from indole-3-acetonitrile in plant-associated bacteria. Agrobacterium and Rhizobium. Proceedings of the National Academy of Science USA, 92 714-8. 

Since this process is involved in thyroxine biosynthesis,14 it is likely that the enzymic oxygenation also involves dioxetanes. The horseradish peroxidase (HRP)-catalyzed oxygenation of indole-3-acetic acid (53) affords electronically excited indole-3-aldehyde (54).83b The a-peroxylactone (2j) was postulated to be responsible for the feeble light... 

Zinc may be involved in the biosynthesis of tryptophan, a precursor of indole-3-acetic acid (lAA) (51). Zinc also participates in the metabolism of the plant as an activator of several enzymes. Zinc may act as an activator for some phosphate transferring enzymes such as hexose kinase or triosephosphate dehydrogenase. Zinc deficiency results in the accumulation of soluble nitrogen compunds such as amides and amino acids (52). Apparently zinc plays an important role in protein synthesis. 

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