IUBMB Enzyme Nomenclature


Accepted name: tryptophan 5-monooxygenase

Reaction: L-tryptophan + tetrahydrobiopterin + O2 = 5-hydroxy-L-tryptophan + 4a-hydroxytetrahydrobiopterin

For diagram click here.

Other name(s): L-tryptophan hydroxylase; indoleacetic acid-5-hydroxylase; tryptophan 5-hydroxylase; tryptophan hydroxylase

Systematic name: L-tryptophan,tetrahydrobiopterin:oxygen oxidoreductase (5-hydroxylating)

Comments: The active centre contains mononuclear iron(II). The enzyme is activated by phosphorylation, catalysed by a Ca2+-activated protein kinase. The 4a-hydroxytetrahydrobiopterin formed can dehydrate to 6,7-dihydrobiopterin, both spontaneously and by the action of EC, 4a-hydroxytetrahydrobiopterin dehydratase. The 6,7-dihydrobiopterin can be enzymically reduced back to tetrahydrobiopterin, by EC (6,7-dihydropteridine reductase), or slowly rearranges into the more stable compound 7,8-dihydrobiopterin.

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 9037-21-2


1. Friedman, P.A., Kappelman, A.H. and Kaufman, S. Partial purification and characterization of tryptophan hydroxylase from rabbit hindbrain. J. Biol. Chem. 247 (1972) 4165-4173. [PMID: 4402511]

2. Hamon, M., Bourgoin, S., Artaud, F. and Glowinski, J. The role of intraneuronal 5-HT and of tryptophan hydroxylase activation in the control of 5-HT synthesis in rat brain slices incubated in K+-enriched medium. J. Neurochem. 33 (1979) 1031-1042. [PMID: 315449]

3. Ichiyama, A., Nakamura, S., Nishizuka, Y. and Hayaishi, O. Enzymic studies on the biosynthesis of serotonin in mammalian brain. J. Biol. Chem. 245 (1970) 1699-1709. [PMID: 5309585]

4. Jequier, E., Robinson, B.S., Lovenberg, W. and Sjoerdsma, A. Further studies on tryptophan hydroxylase in rat brainstem and beef pineal. Biochem. Pharmacol. 18 (1969) 1071-1081. [PMID: 5789774]

5. Wang, L., Erlandsen, H., Haavik, J., Knappskog, P.M. and Stevens, R.C. Three-dimensional structure of human tryptophan hydroxylase and its implications for the biosynthesis of the neurotransmitters serotonin and melatonin. Biochemistry 41 (2002) 12569-12574. [PMID: 12379098]

[EC created 1972, modified 2003]

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