Experimental correlation of substrate position with reaction outcome in the aliphatic halogenase, SyrB2

Ryan J. Martinie, Jovan Livada, Wei Chen Chang, Michael T. Green, Carsten Krebs, J. Martin Bollinger, Alexey Silakov

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72 Scopus citations


The iron(II)- and 2-(oxo)glutarate-dependent (Fe/2OG) oxygenases catalyze an array of challenging transformations, but how individual members of the enzyme family direct different outcomes is poorly understood. The Fe/2OG halogenase, SyrB2, chlorinates C4 of its native substrate, l-threonine appended to the carrier protein, SyrB1, but hydroxylates C5 of l-norvaline and, to a lesser extent, C4 of l-aminobutyric acid when SyrB1 presents these non-native amino acids. To test the hypothesis that positioning of the targeted carbon dictates the outcome, we defined the positions of these three substrates by measuring hyperfine couplings between substrate deuterium atoms and the stable, EPR-active iron-nitrosyl adduct, a surrogate for reaction intermediates. The Fe-2H distances and N-Fe-2H angles, which vary from 4.2 Å and 85° for threonine to 3.4 Å and 65° for norvaline, rationalize the trends in reactivity. This experimental correlation of position to outcome should aid in judging from structural data on other Fe/2OG enzymes whether they suppress hydroxylation or form hydroxylated intermediates on the pathways to other outcomes.

Original languageEnglish (US)
Pages (from-to)6912-6919
Number of pages8
JournalJournal of the American Chemical Society
Issue number21
StatePublished - Jun 3 2015

All Science Journal Classification (ASJC) codes

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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