Reaction: 2-(L-cystein-S-yl)-2-(1H-indol-3-yl)acetonitrile + 2 [reduced NADPH —hemoprotein reductase] + 2 O2 = camalexin + hydrogen cyanide + CO2 + 2 [oxidized NADPH —hemoprotein reductase] + 4 H2O (overall reaction)
(1a) 2-(L-cystein-S-yl)-2-(1H-indol-3-yl)acetonitrile + [reduced NADPH —hemoprotein reductase] + O2 = (R)-dihydrocamalexate + hydrogen cyanide + [oxidized NADPH —hemoprotein reductase] + 2 H2O
(1b) (R)-dihydrocamalexate + [reduced NADPH —hemoprotein reductase] + O2 = camalexin + CO2 + [oxidized NADPH —hemoprotein reductase] + 2 H2O
Glossary: camalexin = 3-(thiazol-2-yl)indole
(R)-dihydrocamalexate = (4R)-2-(1H-indol-3-yl)-4,5-dihydrothiazole-4-carboxylate
Other name(s): CYP71B15 (gene name); bifunctional dihydrocamalexate synthase/camalexin synthase
Systematic name: 2-(cystein-S-yl)-2-(1H-indol-3-yl)-acetonitrile, [reduced NADPH —hemoprotein reductase]:oxygen oxidoreductase (camalexin-forming)
Comments: This cytochrome P-450 (heme thiolate) enzyme, which has been characterized from the plant Arabidopsis thaliana, catalyses the last two steps in the biosynthesis of camalexin, the main phytoalexin in that plant. The enzyme catalyses two successive oxidation events. During the first oxidation the enzyme introduces a C-N double bond, liberating hydrogen cyanide, and during the second oxidation it catalyses a decarboxylation.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Schuhegger, R., Nafisi, M., Mansourova, M., Petersen, B.L., Olsen, C.E., Svatos, A., Halkier, B.A. and Glawischnig, E. CYP71B15 (PAD3) catalyzes the final step in camalexin biosynthesis. Plant Physiol. 141 (2006) 1248-1254. [PMID: 16766671]
2. Böttcher, C., Westphal, L., Schmotz, C., Prade, E., Scheel, D. and Glawischnig, E. 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 (2009) 1830-1845. [PMID: 19567706]