- Alteration of the substrate specificity of the angular dioxygenase carbazole 1,9a-dioxygenase
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Carbazole 1,9a-dioxygenase (CARDO) consists of terminal oxygenase (CARDO-O) and electron transport components. CARDO can catalyze specific oxygenation for various substrates: angular dioxygenation for carbazole and dibenzo-p-dioxin, lateral dioxygenation for anthracene, and monooxygenation for methylene carbon of fluorene and sulfide sulfur of dibenzothiophene. To elucidate the molecular mechanism determining its unique substrate specificity, 17 CARDO-O site-directed mutants at amino acid residues I262, F275, Q282, and F329, which form the substrate-interacting wall around the iron active site by CARDO-O crystal structure, were generated and characterized. F329 replacement dramatically reduced oxygenation activity. However, several mutants produced different products from the wild-type enzyme to a large extent: I262V and Q282Y (1-hydroxycarbazole), F275W (4-hydroxyfluorene), F275A (unidentified cis-dihydrodiol of fluoranthene), and I262A and I262W (monohydroxydibenzothiophenes). These results suggest the possibility that the respective substrates bind to the active sites of CARDO-O mutants in a different orientation from that of the wild-type enzyme.
- Uchimura, Hiromasa,Horisaki, Tadafumi,Umeda, Takashi,Noguchi, Haruko,Usami, Yusuke,Li, Li,Terada, Tohru,Nakamura, Shugo,Shimizu, Kentaro,Takemura, Tetsuo,Habe, Hiroshi,Furihata, Kazuo,Omori, Toshio,Yamane, Hisakazu,Nojiri, Hideaki
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p. 3237 - 3248
(2009/04/10)
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- FLASH-VACUUM PYROLYSIS OF NITROARYLBENZOTRIAZOLES. A TANDEM MASS SPECTROMETRY STUDY
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Tandem mass spectrometry (MS/MS) has been applied to investigate the behaviour of 1-(2-nitrophenyl)benzotriazole upon flash-vacuum pyrolysis (FVP) conditions.Above 500 deg C, is pyrolyzed to give a mixture of 1-nitrocarbazole , 1-hydroxycarbazole and carbazole .Under similar conditions, 2-(2-nitrophenyl)benzotriazole appears to be more stable; it is however partially isomerized into 8 at high temperatures.Aza analogs of 8, like 1-(2-nitro-4-pyridyl)benzotriazole also loose nitrogen above 500 deg C to give a mixture of 1-nitro-3-azacarbazole , 1-hydroxy-3-azacarbazole and 3-azacarbazole .
- Maquestiau, Andre,Flammang-Barbieux, Monique,Flammang, Robert,Chen, Lin-Zhi
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p. 245 - 254
(2007/10/02)
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