title: Discovery of a novel styrene monooxygenase originating from the metagenome.
abstract: Oxygenases form an interesting class of biocatalysts, as they typically perform oxygenations with exquisite chemo-, regio-, and/or enantioselectivity. It has been observed that, once heterologously expressed in Escherichia coli, some oxygenases are able to form the blue pigment indigo. We have exploited this characteristic to screen a metagenomic library derived from loam soil and identified a novel oxygenase. This oxygenase shows 50% sequence identity with styrene monooxygenases from pseudomonads (StyA). Only a limited number of homologs can be found in the genome sequence database, indicating that this biocatalyst is a member of a relatively small family of bacterial monooxygenases. The newly identified monooxygenase catalyzes the epoxidation of styrene and styrene derivatives and forms the corresponding (S)-epoxides with excellent enantiomeric excess [e.g., (S)-styrene oxide is formed with >99% enantiomeric excess, ee] and therefore is named styrene monooxgenase subunit A (SmoA). SmoA shows high enantioselectivity towards aromatic sulfides [e.g., (R)-ethyl phenyl sulfoxide is formed with 92% ee]. This excellent enantioselectivity in combination with the moderate sequence identity forms a clear indication that SmoA from a metagenomic origin represents a new enzyme within the small family of styrene monooxygenases.
authors.affiliation: Laboratory of Biochemistry, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands.
authors.forename: Erik W
authors.initials: EW
authors.lastname: van Hellemond
authors.forename: Dick B
authors.initials: DB
authors.lastname: Janssen
authors.forename: Marco W
authors.initials: MW
authors.lastname: Fraaije
mesh_terms: D004852:Epoxy Compounds / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics*; D016680:Genome, Bacterial / Q000235:genetics*; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D010105:Oxygenases / Q000235:genetics*; D020543:Proteome / Q000235:genetics*; D013237:Stereoisomerism; D013343:Styrenes / Q000378:metabolism
chemical_list: D004852:Epoxy Compounds; D020543:Proteome; D013343:Styrenes; D010105:Oxygenases; C026721:styrene monooxygenase