L-threonyl-[L-threonyl-carrier protein] 4-chlorinase

UniProtKB accession:  Q9RBY6

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UniProtKB description:  Involved in the biosynthesis of syringomycin E, a cyclic lipodepsinonapeptide toxin with phytotoxic activity (PubMed:16002467, PubMed:16528784, PubMed:19245217). Catalyzes the chlorination of L-Thr to 4-Cl-L-Thr when the amino acid is tethered via a thioester linkage to a covalently bound phosphopantetheine cofactor of the carrier protein SyrB1 (L-Thr-S-SyrB1), in a reaction that requires oxygen, chloride ions, ferrous iron and 2-oxoglutarate (PubMed:16002467, PubMed:16528784, PubMed:19245217). In vitro, can catalyze tandem chlorinations at the gamma-position of the threonyl-S-protein substrate (PubMed:16528784). Can also brominate L-Thr-S-SyrB1 in reactions performed with excess sodium bromide, but a preference for chloride versus bromide by a factor of 180 can be estimated by comparing the peak intensities (PubMed:16528784). In addition, in the presence of the nitrogenous anions NO2(-) or N3(-), SyrB2 can direct aliphatic nitration and azidation reactions by the same mechanism as the native halogenation reaction (PubMed:24463698).