title: Possibility of application of cytochrome P450 to bioremediation of dioxins.
abstract: Dioxins, including polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans, and coplanar polychlorinated biphenyls, are known to be metabolized by enzymes such as cytochrome (CYP) P450, angular dioxygenase, lignin peroxidase, and dehalogenase. It is noted that all of these enzymes have metal ions in their active centers, and the enzyme systems except for peroxidase each have a distinct electron transport chain. Among these enzyme systems, we have focused on cytochrome P450-dependent metabolism of dioxins from the viewpoint of practical use for bioremediation. Mammalian and fungal cytochromes P450 showed remarkable activity toward low-chlorinated PCDDs. In particular, mammalian cytochromes P450 belonging to the CYP1 family showed high activity. Rat CYP1A1 showed high activity toward 2,3,7-trichloro-dibenzo-p-dioxin but no detectable activity for 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD). On the basis of these results, we assumed that enlarging the space of the substrate-binding pocket of rat CYP1A1 might generate TCDD-metabolizing enzyme. Large-sized amino acids located at putative substrate-recognition sites and F-G loop were substituted for alanine by site-directed mutagenesis. Finally, we successfully generated 2,3,7,8-TCDD-metabolizing enzyme by site-directed mutagenesis of rat CYP1A1. We hope that recombinant microorganisms harboring genetically engineered cytochrome P450 will be used for bioremediation of soil contaminated with PCDDs, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in the future.
authors.affiliation: Department of Biotechnology, Faculty of Engineering, Toyama Prefectural University, Imizu, Toyama, Japan. tsakaki@pu-toyama.ac.jp
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Sakaki
authors.forename: Keiko
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Shinichi
authors.initials: S
authors.lastname: Ikushiro
mesh_terms: D000818:Animals; D001410:Bacillus megaterium / Q000201:enzymology / Q000378:metabolism; D001673:Biodegradation, Environmental; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D004147:Dioxins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D020075:Phanerochaete / Q000201:enzymology / Q000378:metabolism
chemical_list: D004147:Dioxins; D003577:Cytochrome P-450 Enzyme System