Reaction: L-tryptophan + NADPH + bromide + O2 + H+ = 5-bromo-L-tryptophan + NADP+ + 2 H2O
Other name(s): sktB (gene name); aetF (gene name)
Systematic name: L-tryptophan:NADPH oxidoreductase (5-brominating)
Comments: Contains FAD. The enzyme was isolated from the cyanobacteria Nostoc punctiforme and Aetokthonos hydrillicola. Unlike most other described tryptophan halogenases, the enzyme is self-sufficient and does not require a flavin reductase (single component halogenase). The enzyme from Aetokthonos hydrillicola also catalyses a second bromination reaction at the 7 position. cf. EC 1.14.19.58, tryptophan 5-halogenase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Breinlinger, S., Phillips, T.J., Haram, B.N., Mares, J., Martinez Yerena, J.A., Hrouzek, P., Sobotka, R., Henderson, W.M., Schmieder, P., Williams, S.M., Lauderdale, J.D., Wilde, H.D., Gerrin, W., Kust, A., Washington, J.W., Wagner, C., Geier, B., Liebeke, M., Enke, H., Niedermeyer, T.HJ. and Wilde, S.B. Hunting the eagle killer: A cyanobacterial neurotoxin causes vacuolar myelinopathy. Science 371 (2021) . [PMID: 33766860]
2. Adak, S., Lukowski, A.L., Schafer, R.JB. and Moore, B.S. From tryptophan to toxin: nature's convergent biosynthetic strategy to aetokthonotoxin. J. Am. Chem. Soc. 144 (2022) 2861-2866. [PMID: 35142504]
3. Gafe, S. and Niemann, H.H. Structural basis of regioselective tryptophan dibromination by the single-component flavin-dependent halogenase AetF. Acta Crystallogr D Struct Biol 79 (2023) 596-609. [PMID: 37314407]
4. Chen, C.C., Li, H., Huang, J.W. and Guo, R.T. Structural and molecular insights of two unique enzymes involved in the biosynthesis of a natural halogenated nitrile. FEBS J. 291 (2024) 5123-5132. [PMID: 39308083]
5. Adak, S., Calderone, L.A., Krueger, A., Pandelia, M.E. and Moore, B.S. Single-enzyme conversion of tryptophan to skatole and cyanide expands the mechanistic competence of diiron oxidases. J. Am. Chem. Soc. 147 (2025) 6326-6331. [PMID: 39939147]