Discovery of a thermostable Baeyer–Villiger monooxygenase by genome mining

• Published in: Applied microbiology and biotechnology 2005-01, Vol.66 (4), p.393-400
• Main Authors: Fraaije, Marco W, Wu, Jin, Heuts, Dominic P. H. M, van Hellemond, Erik W, Spelberg, Jeffrey H. Lutje, Janssen, Dick B
• Format: Article
• Language: English
• Subjects: Actinomycetales - enzymology; Actinomycetales - genetics; Amino Acid Sequence; biocatalysts; Biological and medical sciences; Biology of microorganisms of confirmed or potential industrial interest; Biotechnology; E coli; enantiomers; Enzyme Stability; Enzymes; Escherichia coli; Escherichia coli - genetics; Fundamental and applied biological sciences. Psychology; Gene Expression; genome; genome mining; Genome, Bacterial; Genomes; Genomics; half life; heterologous gene expression; ketones; Kinetics; Miscellaneous; Mission oriented research; Mixed Function Oxygenases - chemistry; Mixed Function Oxygenases - genetics; Mixed Function Oxygenases - metabolism; Molecular Sequence Data; Recombinant Proteins - chemistry; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; Sequence Homology, Amino Acid; Spectrophotometry; Stereoisomerism; Substrate Specificity; Sulfur; Temperature; thermal stability; Thermobifida fusca
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-004-1749-5

Baeyer–Villiger monooxygenases represent useful biocatalytic tools, as they can catalyze reactions which are difficult to achieve using chemical means. However, only a limited number of these atypical monooxygenases are available in recombinant form. Using a recently described protein sequence motif, a putative Baeyer–Villiger monooxygenase (BVMO) was identified in the genome of the thermophilic actinomycete Thermobifida fusca. Heterologous expression of the respective protein in Escherichia coli and subsequent enzyme characterization showed that it indeed represents a BVMO. The NADPH-dependent and FAD-containing monooxygenase is active with a wide range of aromatic ketones, while aliphatic substrates are also converted. The best substrate discovered so far is phenylacetone (kcₐₜ = 1.9 s⁻¹, KM = 59 μM). The enzyme exhibits moderate enantioselectivity with α-methylphenylacetone (enantiomeric ratio of 7). In addition to Baeyer–Villiger reactions, the enzyme is able to perform sulfur oxidations. Different from all known BVMOs, this newly identified biocatalyst is relatively thermostable, displaying an activity half-life of 1 day at 52°C. This study demonstrates that, using effective annotation tools, genomes can efficiently be exploited as a source of novel BVMOs.