Marine microbial dehalogenase removes unwanted bromine

Although the marine natural product pentabromopseudilin was first characterized 50 years ago, its biosynthesis is still not completely understood. Researchers at the University of California, San Diego, have now determined that, in addition to enzymes for adding bromines to the molecule, the biosynthetic pathway for pentabromopseudilin also includes an enzyme for removing bromine (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b08512). A set of enzymes in the pathway catalyzes the synthesis of the needed precursors. But one of those precursors has one too many bromines. The enzymes make 2,3,4,5-tetrabromopyrrole when what’s really needed is 2,3,4-tribromopyrrole. Bradley S. Moore and coworkers have identified Bmp8 as the enzyme responsible for the required dehalogenation. After Bmp8 removes the unwanted bromine via a redox thiol mechanism involving a specific cysteine residue, another enzyme couples the tribromopyrrole to 2,4-dibromophenol to form pentabromopseudilin. The enzymatic dehalogenation of man-made persistent organic pollutants is well-known, but to the best of the researchers’ knowledge, Bmp8 is the first example of a marine microbial dehalogenase that’s involved in the biosynthesis of a halogenated natural product.