IUBMB Enzyme Nomenclature


Accepted name: tryptophan 5-halogenase

Reaction: L-tryptophan + FADH2 + chloride + O2 + H+ = 5-chloro-L-tryptophan + FAD + 2 H2O

For diagram of reaction click here.

Other name(s): pyrH (gene name)

Systematic name: L-tryptophan:FADH2 oxidoreductase (5-halogenating)

Comments: A flavin-dependent halogenase. The enzyme from the bacterium Streptomyces rugosporus catalyses halogenation of the C-5 position of tryptophan during the biosynthesis of the antibiotic compound pyrroindomycin B. It utilizes molecular oxygen to oxidize the FADH2 cofactor, giving C4a-hydroperoxyflavin, which then reacts with chloride to produce a hypochlorite ion. The latter reacts with an active site lysine to generate a chloramine, which chlorinates the substrate. cf. EC, tryptophan 6-halogenase and EC, tryptophan 7-halogenase.

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


1. Zehner, S., Kotzsch, A., Bister, B., Sussmuth, R.D., Mendez, C., Salas, J.A. and van Pee, K.H. A regioselective tryptophan 5-halogenase is involved in pyrroindomycin biosynthesis in Streptomyces rugosporus LL-42D005. Chem. Biol. 12 (2005) 445-452. [PMID: 15850981]

2. Zhu, X., De Laurentis, W., Leang, K., Herrmann, J., Ihlefeld, K., van Pee, K.H. and Naismith, J.H. Structural insights into regioselectivity in the enzymatic chlorination of tryptophan. J. Mol. Biol. 391 (2009) 74-85. [PMID: 19501593]

[EC created 2018]

Return to EC 1.14.19 home page
Return to EC 1.14 home page
Return to EC 1 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page