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.
Department of Microbiology, University of Iowa, Iowa City 52242, USA. sol-resnick@uiowa.edu
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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