Structural highlights
Function
[REBH_NOCAE] Involved in the biosynthesis of the indolocarbazole antitumor agent rebeccamycin. Catalyze the chlorination of tryptophan (Trp) at C7 position to yield 7-chlorotryptophan. The reaction between FADH2, Cl-, and O2 generates the powerful oxidant HOCl, which is presumed to carry out the chlorination reaction. The reaction of HOCl with the active site Lys-79 generates a lysine chloramine, which plays a key role in directing regiospecific chlorination of substrate in this important class of biosynthetic enzymes. It is also able to use bromide ions to generate monobrominated Trp.[1] [2] [3]
Publication Abstract from PubMed
We previously reported that the halogenase RebH catalyzes selective halogenation of several heterocycles and carbocycles, but product yields were limited by enzyme instability. Here, we use directed evolution to engineer an RebH variant, 3-LR, with a Topt over 5 degrees C higher than that of wild-type, and 3-LSR, with a Tm 18 degrees C higher than that of wild-type. These enzymes provided significantly improved conversion (up to fourfold) for halogenation of tryptophan and several non-natural substrates. This initial evolution of RebH not only provides improved enzymes for immediate synthetic applications, but also establishes a robust protocol for further halogenase evolution.
Improving the Stability and Catalyst Lifetime of the Halogenase RebH By Directed Evolution.,Poor CB, Andorfer MC, Lewis JC Chembiochem. 2014 May 21. doi: 10.1002/cbic.201300780. PMID:24849696[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Sanchez C, Butovich IA, Brana AF, Rohr J, Mendez C, Salas JA. The biosynthetic gene cluster for the antitumor rebeccamycin: characterization and generation of indolocarbazole derivatives. Chem Biol. 2002 Apr;9(4):519-31. PMID:11983340
- ↑ Yeh E, Garneau S, Walsh CT. Robust in vitro activity of RebF and RebH, a two-component reductase/halogenase, generating 7-chlorotryptophan during rebeccamycin biosynthesis. Proc Natl Acad Sci U S A. 2005 Mar 15;102(11):3960-5. Epub 2005 Mar 2. PMID:15743914 doi:http://dx.doi.org/10.1073/pnas.0500755102
- ↑ Yeh E, Blasiak LC, Koglin A, Drennan CL, Walsh CT. Chlorination by a long-lived intermediate in the mechanism of flavin-dependent halogenases. Biochemistry. 2007 Feb 6;46(5):1284-92. PMID:17260957 doi:10.1021/bi0621213
- ↑ Poor CB, Andorfer MC, Lewis JC. Improving the Stability and Catalyst Lifetime of the Halogenase RebH By Directed Evolution. Chembiochem. 2014 May 21. doi: 10.1002/cbic.201300780. PMID:24849696 doi:http://dx.doi.org/10.1002/cbic.201300780
