Direct nitration and azidation of aliphatic carbons by an iron-dependent halogenase

• Published in: Nature chemical biology Vol. 10; no. 3; pp. 209 - 215
• Main Authors: Matthews, Megan L, Chang, Wei-chen, Layne, Andrew P, Miles, Linde A, Krebs, Carsten, Bollinger, J Martin
• Format: Journal Article
• Language: English
• Published: New York Nature Publishing Group US 01.03.2014; Nature Publishing Group
• Subjects: 631/92/173; 631/92/60; 631/92/603; 631/92/612/1141; 82; Anions; Azides - chemistry; Biochemical Engineering; Biochemistry; Bioorganic Chemistry; Cell Biology; Chemical bonds; Chemistry; Chemistry/Food Science; Chromatography, Liquid; Coordination Complexes - chemistry; Enzymes; Enzymes - metabolism; Halogenation; Iron; Iron - chemistry; Ketoglutaric Acids - chemistry; Mass Spectrometry; Mutation; Nitrates - chemistry; Pseudomonas syringae - enzymology; Pseudomonas syringae - genetics; Substrates
• ISSN: 1552-4450; 1552-4469
• DOI: 10.1038/nchembio.1438

Halogenases differ from hydroxylases by coordination of a chloride ion at the reactive iron center, which is taken up by an activated substrate. Biochemical and spectroscopic evidence now show other anions can be used, resulting in the first enzymatic incorporation of nitrogen onto unactivated aliphatic carbons. Iron-dependent halogenases employ cis -halo-Fe( IV )-oxo (haloferryl) complexes to functionalize unactivated aliphatic carbon centers, a capability elusive to synthetic chemists. Halogenation requires (i) coordination of a halide anion (Cl − or Br − ) to the enzyme's Fe( II ) cofactor, (ii) coupled activation of O 2 and decarboxylation of α-ketoglutarate to generate the haloferryl intermediate, (iii) abstraction of hydrogen (H•) from the substrate by the ferryl and (iv) transfer of the cis halogen as Cl• or Br• to the substrate radical. This enzymatic solution to an unsolved chemical challenge is potentially generalizable to installation of other functional groups, provided that the corresponding anions can support the four requisite steps. We show here that the wild-type halogenase SyrB2 can indeed direct aliphatic nitration and azidation reactions by the same chemical logic. The discovery and enhancement by mutagenesis of these previously unknown reaction types suggest unrecognized or untapped versatility in ferryl-mediated enzymatic C-H bond activation.