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Structural and catalytic characterization of a fungal Baeyer-Villiger monooxygenase

DOI: 10.1371/journal.pone.0160186 DOI Help

Authors: Felix Martin Ferroni (University of the Free State) , Carmien Tolmie (University of the Free State) , Martha Sophia Smit (University of the Free State) , Diederik Opperman (University of the Free State)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Plos One , VOL 11

State: Published (Approved)
Published: July 2016
Diamond Proposal Number(s): 12255

Open Access Open Access

Abstract: Baeyer-Villiger monooxygenases (BVMOs) are biocatalysts that convert ketones to esters. Due to their high regio-, stereo- and enantioselectivity and ability to catalyse these reactions under mild conditions, they have gained interest as alternatives to chemical Baeyer-Villiger catalysts. Despite their widespread occurrence within the fungal kingdom, most of the currently characterized BVMOs are from bacterial origin. Here we report the catalytic and structural characterization of BVMOAFL838 from Aspergillus flavus. BVMOAFL838 converts linear and aryl ketones with high regioselectivity. Steady-state kinetics revealed BVMOAFL838 to show significant substrate inhibition with phenylacetone, which was more pronounced at low pH, enzyme and buffer concentrations. Para substitutions on the phenyl group significantly improved substrate affinity and increased turnover frequencies. Steady-state kinetics revealed BVMOAFL838 to preferentially oxidize aliphatic ketones and aryl ketones when the phenyl group are separated by at least two carbons from the carbonyl group. The X-ray crystal structure, the first of a fungal BVMO, was determined at 1.9 Å and revealed the typical overall fold seen in type I bacterial BVMOs. The active site Arg and Asp are conserved, with the Arg found in the “in” position. Similar to phenylacetone monooxygenase (PAMO), a two residue insert relative to cyclohexanone monooxygenase (CHMO) forms a bulge within the active site. Approximately half of the “variable” loop is folded into a short α-helix and covers part of the active site entry channel in the non-NADPH bound structure. This study adds to the current efforts to rationalize the substrate scope of BVMOs through comparative catalytic and structural investigation of different BVMOs.

Journal Keywords: Ketones; Crystal structure; Enzyme purification; Fungal structure; Enzyme inhibitors; Benzaldehydes; Oxidation; Cofactors (biochemistry)

Diamond Keywords: Enzymes; Fungi

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I04-1-Macromolecular Crystallography (fixed wavelength)

Added On: 23/11/2016 13:55


Discipline Tags:

Biochemistry Catalysis Chemistry Structural biology Life Sciences & Biotech

Technical Tags:

Diffraction Macromolecular Crystallography (MX)