Selective hydroxylation of alkanes by an extracellular fungal peroxygenase

Sebastian Peter, Matthias Kinne, Xiaoshi Wang, René Ullrich, Gernot Kayser, John T. Groves, Martin Hofrichter

Research output: Contribution to journalArticlepeer-review

67 Scopus citations

Abstract

Fungal peroxygenases are novel extracellular heme-thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H2O2 as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H2O2-dependent hydroxylation of linear alkanes at the 2-position and 3-position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n-heptane and n-octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)-enantiomer of the corresponding 3-alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H 218O2 resulted in complete incorporation of 18O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n-hexane-1,1,1,2,2,3,3-D7 showed a large intramolecular deuterium isotope effect [(kH/kD) obs] of 16.0 ± 1.0 for 2-hexanol and 8.9 ± 0.9 for 3-hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 à- 1011 s-1. These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long-chain alkanes (> C 16) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane-containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H2O2-dependent hydroxylation of linear alkanes at the 2- and 3-position with high efficiency as well as the regioselective monooxygenation of branched and cyclic alkanes. In addition, we report data for peroxygenase solvent stability tests, chiral separations, an H218O2-labelling study, intramolecular deuterium isotope effect determinations and radical clock experiments.

Original languageEnglish (US)
Pages (from-to)3667-3675
Number of pages9
JournalFEBS Journal
Volume278
Issue number19
DOIs
StatePublished - Oct 2011

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Keywords

  • P450
  • alkane
  • hydroxylation
  • peroxygenase
  • radical clock

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