MetaCyc Pathway: camalexin biosynthesis

Pathway diagram: camalexin biosynthesis

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 Secondary Metabolites Biosynthesis Phytoalexins Biosynthesis Indole Phytoalexins Biosynthesis

Some taxa known to possess this pathway include ? : Arabidopsis thaliana col

Expected Taxonomic Range: Brassicales

Camalexin is the main phytoalexin in Arabidopsis. It is involved in plant defense and has cancer-preventive property. The accumulation of camalexin in Arabidopsis is induced by a variety of microorganisms including bacteria, fungi and oomycetes.

Camalexin was previously proposed to be derived from indole-3-carboxaldehyde, independent of tryptophan. Recently, genetic evidence showed that camalexin is directly derived from tryptophan via indole-3-acetaldoxime, a branch point metabolite that also leads to the biosynthesis of secondary metabolites glucosinolates (glucosinolate biosynthesis from tryptophan) and the plant hormone IAA (indole-3-acetate biosynthesis II). Double-mutants of CYP79B2 and CYP79B3 were devoid of camalexin [Glawischnig04]. Indole-3-acetaldoxime is consequently converted to indole-3-acetonitrile (IAN) by CYP71A13 [Nafisi07].

In vivo feeding experiments suggested that the thiazole ring of camalexin is derived from cysteine [Zook97]. The exact steps of the thiazole ring formation remained elusive until recently. In a metabolomics study, the IAN conjugate Cys(IAN) was found to be an intermediate of camalexin biosynthesis. The formation of Cys(IAN) possibly proceeds via intermediates γGluCYs(IAN)Gly and γGluCYs(IAN). Accumulation of these three compounds was detected in CYP71B15 mutants in an in vivo feeding experiment [Bolduc09]. CYP71B15 was previously shown to catalyze the last step of camalexin biosynthesis, converting dihydrocamalexin (DHCA) to camalexin. CYP71B15 is a novel plant enzyme in that it is the only known cytochrome P450 in plants results in simultaneous decarboxylation and introduction of a C-C double bond [Schuhegger06]. More interestingly, CYP71B15 is recently found a multifunctional enzyme that also catalyzes the NADPH-dependent conversions of Cys(IAN) to DHCA [Bottcher09]. During the conversion of one molecule Cys(IAN) to DHCA, one molecule of cyanide is released. In planta accumulation of cyanide may shut down the CYP P450 catalyzed camalexin biosynthesis process and thus cyanide is possibly detoxified via the cyanide detoxification pathway (cyanide detoxification I).

The biosynthetic pathway is coordinately induced, strictly localized to the site of pathogen infection [Glawischnig06].

Unification Links: AraCyc:CAMALEXIN-SYN

Revised 18-Sep-2006 by Zhang P
Revised 13-Sep-2010 by Zhang P


Bolduc09: Bolduc N, Hake S (2009). "The maize transcription factor KNOTTED1 directly regulates the gibberellin catabolism gene ga2ox1." Plant Cell 21(6);1647-58. PMID: 19567707

Bottcher09: Bottcher C, Westphal L, Schmotz C, Prade E, Scheel D, Glawischnig E (2009). "The multifunctional enzyme CYP71B15 (PHYTOALEXIN DEFICIENT3) converts cysteine-indole-3-acetonitrile to camalexin in the indole-3-acetonitrile metabolic network of Arabidopsis thaliana." Plant Cell 21(6);1830-45. PMID: 19567706

Glawischnig04: Glawischnig E, Hansen BG, Olsen CE, Halkier BA (2004). "Camalexin is synthesized from indole-3-acetaldoxime, a key branching point between primary and secondary metabolism in Arabidopsis." Proc Natl Acad Sci U S A 101(21);8245-50. PMID: 15148388

Glawischnig06: Glawischnig E (2006). "The role of cytochrome P450 enzymes in the biosynthesis of camalexin." Biochem Soc Trans 34(Pt 6);1206-8. PMID: 17073786

Nafisi07: Nafisi M, Goregaoker S, Botanga CJ, Glawischnig E, Olsen CE, Halkier BA, Glazebrook J (2007). "Arabidopsis cytochrome P450 monooxygenase 71A13 catalyzes the conversion of indole-3-acetaldoxime in camalexin synthesis." Plant Cell 19(6);2039-52. PMID: 17573535

Schuhegger06: Schuhegger R, Nafisi M, Mansourova M, Petersen BL, Olsen CE, Svatos A, Halkier BA, Glawischnig E (2006). "CYP71B15 (PAD3) catalyzes the final step in camalexin biosynthesis." Plant Physiol 141(4);1248-54. PMID: 16766671

Zook97: Zook M, Hammerschmidt R (1997). "Origin of the thiazole ring of camalexin, a phytoalexin from Arabidopsis thaliana." Plant Physiol 113(2);463-8. PMID: 9046593

Other References Related to Enzymes, Genes, Subpathways, and Substrates of this Pathway

Hull00: Hull AK, Vij R, Celenza JL (2000). "Arabidopsis cytochrome P450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis." Proc Natl Acad Sci U S A 2000;97(5);2379-84. PMID: 10681464

Jin10: Jin JM, Lee S, Lee J, Baek SR, Kim JC, Yun SH, Park SY, Kang S, Lee YW (2010). "Functional characterization and manipulation of the apicidin biosynthetic pathway in Fusarium semitectum." Mol Microbiol 76(2);456-66. PMID: 20233305

Kumar63: Kumar, S.A., Mahadevan, S. (1963). "3-indoleacetaldoxime hydro-lyaseE: a pyridoxal-5'-phosphate activated enzyme." Arch Biochem Biophys 103;516-8. PMID: 14099566

Latendresse13: Latendresse M. (2013). "Computing Gibbs Free Energy of Compounds and Reactions in MetaCyc."

Mikkelsen00: Mikkelsen MD, Hansen CH, Wittstock U, Halkier BA (2000). "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 275(43);33712-7. PMID: 10922360

Naur03: Naur P, Hansen CH, Bak S, Hansen BG, Jensen NB, Nielsen HL, Halkier BA (2003). "CYP79B1 from Sinapis alba converts tryptophan to indole-3-acetaldoxime." Arch Biochem Biophys 409(1);235-41. PMID: 12464264

Shukla68: Shukla PS, Mahadevan S (1968). "Indoleacetaldoxime hydro-lyase. II. Purification and properties." Arch Biochem Biophys 125(3);873-83. PMID: 5671050

Zhao02: Zhao Y, Hull AK, Gupta NR, Goss KA, Alonso J, Ecker JR, Normanly J, Chory J, Celenza JL (2002). "Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3." Genes Dev 16(23);3100-12. PMID: 12464638

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Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Wed Jul 1, 2015, BIOCYC13A.