Regio- and stereospecific oxidation of fluorene, dibenzofuran, and dibenzothiophene by naphthalene dioxygenase from Pseudomonas sp. strain NCIB 9816-4.
The regio- and stereospecific oxidation of fluorene, dibenzofuran, and dibenzothiophene was examined with mutant and recombinant strains expressing naphthalene dioxygenase from Pseudomonas sp. strain NCIB 9816-4. The initial oxidation products were isolated and identified by gas chromatography-mass spectrometry and nuclear magnetic resonance spectrometry. Salicylate-induced cells of Pseudomonas sp. strain 9816/11 and isopropyl-beta-D-thiogalactopyranoside-induced cells of Escherichia coli JM109(DE3)(pDTG141) oxidized fluorene to (+)-(3S,4R)-cis-3,4-dihydroxy-3,4-dihydrofluorene (80 to 90% relative yield; > 95% enantiomeric excess [ee]) and 9-fluorenol (< 10% yield). The same cells oxidized dibenzofuran to (1R,2S)-cis-1,2-dihydroxy-1, 2-dihydrodibenzofuran (60 to 70% yield; > 95% ee) and (3S,4R)-cis-3, 4-dihydroxy-3,4-dihydrodibenzofuran (30 to 40% yield; > 95% ee). Induced cells of both strains, as well as the purified dioxygenase, also oxidized dibenzothiophene to (+)-(1R,2S)-cis-1,2-dihydroxy-1, 2-dihydrodibenzothiophene (84 to 87% yield; > 95% ee) and dibenzothiophene sulfoxide (< 15% yield). The major reaction catalyzed by naphthalene dioxygenase with each substrate was stereospecific dihydroxylation in which the cis-dihydrodiols were of identical regiochemistry and of R configuration at the benzylic center adjacent to the bridgehead carbon atom. The regiospecific oxidation of dibenzofuran differed from that of the other substrates in that a significant amount of the minor cis-3,4-dihydrodiol regioisomer was formed. The results indicate that although the absolute stereochemistry of the cis-diene diols was the same, the nature of the bridging atom or heteroatom influenced the regiospecificity of the reactions catalyzed by naphthalene dioxygenase.
Resnick
S M
SM
Department of Microbiology, University of Iowa, Iowa City 52242, USA. sol-resnick@uiowa.edu
Gibson
D T
DT
D001572:Benzofurans / Q000737:chemistry / Q000378:metabolism; D001711:Biotransformation; D049308:Dioxygenases; D004926:Escherichia coli / Q000235:genetics; D005449:Fluorenes / Q000737:chemistry / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology* / Q000235:genetics; D011995:Recombination, Genetic; D013237:Stereoisomerism; D013379:Substrate Specificity; D013876:Thiophenes / Q000737:chemistry / Q000378:metabolism
D001572:Benzofurans; D005449:Fluorenes; D009097:Multienzyme Complexes; D013876:Thiophenes; C041509:fluorene; C023614:dibenzofuran; D010105:Oxygenases; D049308:Dioxygenases; C038703:naphthalene dioxygenase; C016366:dibenzothiophene