4lu6
From Proteopedia
Thermostabilized RebH
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 PubMedWe 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
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