Indole-3-acetaldoxime

Hull et al.35 used a different approach to identify CYP79B2 and CYP79B3 from Arabidopsis as enzymes for the conversion of tryptophan to indole-3-acetaldoxime (LAOx) (Fig. 8.4). They took advantage of the fact that an analog of indole, 5-fluoroindole, is toxic to yeast, and they screened for yeast colonies containing Arabidopsis cDNAs that were resistant to the analog. 

Figure 8.4 Glucosinolate and IAA pathways. IAA indole-3-acetic acid IAN indole-3-acetonitrile IAOx indole-3-acetaldoxime. A loss of function of CYP83B drives the IAOx to IAA and an auxin-overproducing phenotype is the result.

MIKKELSEN, M.D., HANSEN, C.H., WITTSTOCK, U., HALKIER, B.A., Cytochrome P450 CYP79B2 from Arabidopsis catalyzes the conversion of tryptophan to indole-3-acetaldoxime, a precursor of indole glucosinolates and indole-3-acetic acid, J. Biol. Chem., 2000, 275,33712-33717. 

LUDWIG-MULLER, J., HILGENBERG, W., A plasma membrane-bound enzyme oxidases L-tryptophan to indole-3-acetaldoxime, Physiol. Plant., 1988, 74, 240-250. 

LUDWIG-MULLER, J., RAUSCH, T., LANG, S HILGENBERG, W Plasma membrane-bound high plant isoenzymes convert tryptophan to indole-3-acetaldoxime, Phytochemistry, 1990, 29, 1397-1400. 

RAJAGOPAL, R., LARSEN, P., Metabolism of indole-3-acetaldoxime in plants, Planta, 1972,103,45-54. 

HELMLINGER, J., RAUCH, T., HILGENBERG, W., Metabolism of, 4C-indole-3-acetaldoxime by hypocotyls of Chinese cabbage, Phytochemistry, 1985, 24, 2497-2502. 

HELMINGER, J., RAUSCH, T HILGENBERG, W., A soluble protein factor from Chinese cabbage converts indole-3-acetaldoxime to IAA, Phytochemistry, 1987, 26, 615-618. 

Indole-3-acetaldoxime (30) and 4-hydroxyphenylacetaldoxime were shown to be metabolized by plant and pest fungi to 32 and to other related indole- and 4-hydroxyphenyl carboxylic acids, however, the biochemical transformation differed between the two fungi. These biochemical transformations may be relevant to the ability of certain fungi to cause plant diseases . Compound 30 has been shown to be a key intermediate in the biosynthesis of camalexin, 3-thiazolyl-2 -yl-indole, a member of the family of phytoalexins that are produced in response to pathogen attack. It was demonstrated that CYP71A13 catalyzes the conversion of 30 to indole-3-acetonitrile, which is essential for the biosynthesis of camalexin. Thus, the literature supplies a large body of evidence for the existence of a set of enzymes dedicated to the production of the auxin, 32, from tryptophan via indole-3-acetaldoxime (30). 

Mikkelsen, M.D., Naur, P. and Halkier, B.A. (2004) Arabidopsis mutants in the C-S lyase of glucosinolate biosynthesis establish a critical role for indole-3-acetaldoxime in auxin homeostasis. Plant., 37, 770-77. 

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 544 Proposed camalexin biosynthetic pathway in Arabidopsis. Trp, tryptophan lAOx, indole-3-acetaldoxime IAN, indole-3-acetonitrile DHCA, dihydrocamalexic acid. Enzymes CYP79B2, CYP79B3, CYP71A13, CYP71B15, cytochrome P450 monooxygenases GSTF6, glutathione 5-transferase GGPl, y-glutamyl peptidase.

A13 Conversion of indole-3-acetaldoxime to indole-3-acetonitrile Camalexin [45]... 

B1 Oxidation of indole-3-acetaldoxime Indole glucosinolates [37]... 

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