title: Dibenzofuran 4,4a-dioxygenase from Sphingomonas sp. strain RW1: angular dioxygenation by a three-component enzyme system.
abstract: Sphingomonas sp. strain RW1 synthesized a constitutive enzyme system that oxygenated dibenzofuran (DBF) to 2,2',3-trihydroxybiphenyl (THB). We purified this dibenzofuran 4,4a-dioxygenase system (DBFDOS) and found it to consist of four components which catalyzed three activities. Two isofunctional, monomeric flavoproteins (components A1 and A2; M(r) of about 44,000) transferred electrons from NADH to the second component (B; M(r) of about 12,000), a ferredoxin, which transported electrons to the heteromultimeric (alpha 2 beta 2) oxygenase component (C; M(r) of alpha, 45,000; M(r) of beta, 23,000). DBFDOS consumed 1 mol each of NADH, O2, and DBF, which was dioxygenated to about 1 mol of THB; no intermediate was observed. The reaction was thus the dioxygenation of DBF at the 4 and 4a positions to give a diene-diol-hemiacetal which rearomatized by spontaneous loss of a phenolate group to form THB. Components A1 and A2 each reduced dichlorophenolindophenol but had negligible activity with cytochrome c; each lost the yellow color, observed to be flavin adenine dinucleotide, upon purification. Component B, which transported electrons to the oxygenase or cytochrome c, had an N-terminal amino acid sequence with high homology to the putidaredoxin of cytochrome P-450cam. The oxygenase had the UV spectrum of a Rieske iron-sulfur center. We presume DBFDOS to be a class IIA dioxygenase system (EC 1.14.12.-), functionally similar to pyrazon dioxygenase.
authors.affiliation: Institute of Microbiology, Swiss Federal Institute of Technology, Zürich.
authors.forename: P V
authors.initials: PV
authors.lastname: Bünz
authors.forename: A M
authors.initials: AM
authors.lastname: Cook
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000201:enzymology*; D001572:Benzofurans / Q000378:metabolism*; D005288:Ferredoxins / Q000737:chemistry; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D010105:Oxygenases / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D001572:Benzofurans; D005288:Ferredoxins; C023614:dibenzofuran; D010088:Oxidoreductases; D010105:Oxygenases