Selective hydroxylation of alkanes by an extracellular fungal peroxygenase
| Autor: | Matthias Kinne, René Ullrich, Gernot Kayser, Sebastian Peter, Xiaoshi Wang, Martin Hofrichter, John T. Groves |
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| Rok vydání: | 2011 |
| Předmět: |
Alkane
chemistry.chemical_classification 0303 health sciences Cyclohexanol Cell Biology 010402 general chemistry Hydrogen atom abstraction 01 natural sciences Biochemistry 0104 chemical sciences Hydroxylation 03 medical and health sciences chemistry.chemical_compound chemistry Unspecific peroxygenase Radical clock Organic chemistry Molecular Biology Mixed Function Oxygenases 030304 developmental biology Norcarane |
| Zdroj: | FEBS Journal. 278:3667-3675 |
| ISSN: | 1742-464X |
| DOI: | 10.1111/j.1742-4658.2011.08285.x |
| Popis: | 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 H218O2 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 × 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 (> C16) 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. |
| Databáze: | OpenAIRE |
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