title: The role of the Sphingomonas species UG30 pentachlorophenol-4-monooxygenase in p-nitrophenol degradation.
abstract: Pentachlorophenol-4-monooxygenase is an aromatic flavoprotein monooxygenase which hydroxylates pentachlorophenol and a wide range of polyhalogenated phenols at their para position. The PCP-degrading Sphingomonas species UG30 was recently shown to mineralize p-nitrophenol. In this study, the UG30 pcpB gene encoding the pentachlorophenol-4-monooxygenase gene was cloned for use to study its potential role in p-nitrophenol degradation. The UG30 pcpB gene consists of 1614 bp with a predicted translational product of 538 amino acids and a molecular mass of 59,933 Da. The primary sequence of pentachlorophenol-4-monooxygenase contained a highly conserved FAD binding site at its N-terminus associated with a beta alpha beta fold. UG30 has been shown previously to convert p-nitrophenol to 4-nitrocatechol. We observed that pentachlorophenol-4-monooxygenase catalyzed the hydroxylation of 4-nitrocatechol to 1,2,4-benzenetriol. About 31.2% of the nitro substituent of 4-nitrocatechol (initial concentration of 200 microM) was cleaved to yield nitrite over 2 h, indicating that the enzyme may be involved in the second step of p-nitrophenol degradation. The enzyme also hydroxylated p-nitrophenol at the para position, but only to a very slight extent. Our results confirm that pentachlorophenol-4-monooxygenase is not the primary enzyme in the initial step of p-nitrophenol metabolism by UG30.
authors.affiliation: Department of Environmental Biology, University of Guelph, Ont., Canada.
authors.forename: K T
authors.initials: KT
authors.lastname: Leung
authors.forename: S
authors.initials: S
authors.lastname: Campbell
authors.forename: Y
authors.initials: Y
authors.lastname: Gan
authors.forename: D C
authors.initials: DC
authors.lastname: White
authors.forename: H
authors.initials: H
authors.lastname: Lee
authors.forename: J T
authors.initials: JT
authors.lastname: Trevors
mesh_terms: D001673:Biodegradation, Environmental; D002396:Catechols / Q000378:metabolism; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D016946:Gram-Negative Aerobic Rods and Cocci / Q000201:enzymology* / Q000235:genetics*; D006899:Mixed Function Oxygenases / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D009596:Nitrophenols / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
chemical_list: D002396:Catechols; D009596:Nitrophenols; D006899:Mixed Function Oxygenases; C069781:pentachlorophenol monooxygenase; C001833:4-nitrocatechol; C024836:4-nitrophenol