IUBMB Enzyme Nomenclature


Accepted name: tryptophan N-monooxygenase

Reaction: L-tryptophan + 2 O2 + 2 NADPH + 2 H+ = (E)-indol-3-ylacetaldoxime + 2 NADP+ + CO2 + 3 H2O (overall reaction)
(1a) L-tryptophan + O2 + NADPH + H+ = N-hydroxy-L-tryptophan + NADP+ + H2O
(1b) N-hydroxy-L-tryptophan + O2 + NADPH + H+ = N,N-dihydroxy-L-tryptophan + NADP+ + H2O
(1c) N,N-dihydroxy-L-tryptophan = (E)-indol-3-ylacetaldoxime + CO2 + H2O

Other name(s): tryptophan N-hydroxylase; CYP79B1; CYP79B2; CYP79B3

Systematic name: L-tryptophan,NADPH:oxygen oxidoreductase (N-hydroxylating)

Comments: A heme-thiolate protein (P-450). This enzyme catalyses two successive N-hydroxylations of L-tryptophan, the first steps in the biosynthesis of the both auxin and the indole alkaloid phytoalexin camalexin. The product of the two hydroxylations, N,N-dihydroxy-L-tryptophan, is extremely labile and dehydrates spontaneously.The dehydrated product is then subject to a decarboxylation that produces the oxime. It is still not known whether the decarboxylation is spontaneous or catalysed by the enzyme. The product, (E)-indol-3-ylacetaldoxime, undergoes a spontaneous isomerization to the (Z) form.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, CAS registry number:


1. Mikkelsen, M.D., Hansen, C.H., Wittstock, U. and 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. 275 (2000) 33712-33717. [PMID: 10922360]

2. Hull, A.K., Vij, R. and Celenza, J.L. Arabidopsis cytochrome P450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis. Proc. Natl. Acad. Sci. USA 97 (2000) 2379-2384. [PMID: 10681464]

3. Zhao, Y., Hull, A.K., Gupta, N.R., Goss, K.A., Alonso, J., Ecker, J.R., Normanly, J., Chory, J. and Celenza, J.L. Trp-dependent auxin biosynthesis in Arabidopsis: involvement of cytochrome P450s CYP79B2 and CYP79B3. Genes Dev. 16 (2002) 3100-3112. [PMID: 12464638]

4. Naur, P., Hansen, C.H., Bak, S., Hansen, B.G., Jensen, N.B., Nielsen, H.L. and Halkier, B.A. CYP79B1 from Sinapis alba converts tryptophan to indole-3-acetaldoxime. Arch. Biochem. Biophys. 409 (2003) 235-241. [PMID: 12464264]

[EC created 2011]

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