Intermediate and mechanism of hydroxylation of o-iodophenol by salicylate hydroxylase
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金沢大学自然科学研究科
金沢大学理工研究域自然システム学系
Salicylate hydroxylase [EC 1.14.13.1] from Pseudomonas putida catalyzes the hydroxylation of salicylate, and also o-aminophenol, o-nitrophenol, and o-halogenophenols, to catechol. The reactions with these o-substituted phenols comprise oxygenative deamination, denitration, and dehalogenation, respectively. The reaction try, as to NADH oxidized, oxygen consumed, and catechol formed, is 2 : 1 : 1, respectively. The mechanisms for the deiodination and oxygenation of o-iodophenol were investigated in detail by the use of I+-trapping reagents such as DL-methionine, 2-chlorodimedone, and L-tyrosine. The addition of the traps did not change the molar ratio of catechol formed to NADH oxidized, nor iodinated traps produced were in the incubation mixture. The results suggest that I+ was not produced on the deiodination in the hydroxylation of o-iodophenol. On the other hand, L-ascorbate, L-epinephrine, and phenylhydrazine increased the molar ratio. o-Phenylenediamine decreased it, being converted to phenazine. This suggests that o-benzoquinone is formed in the oxidation of o-iodophenol as a nascent product. The quinone was detected spectrophotometrically by means of the stopped-flow method. Kinetic analysis of the reactions revealed that o-benzoquinone is reduced nonenzymatically to catechol by a second molecule of NADH. A mechanism of elimination for the ortho-substituted groups of substrate phenols by the enzyme is proposed and discussed.
収録刊行物
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- Journal of Biochemistry
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Journal of Biochemistry 109 (5), 791-797, 1991-01-01
日本生化学会 = Japanese Biochemical Society
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詳細情報 詳細情報について
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- CRID
- 1390853650131604608
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- NII論文ID
- 130006864524
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- NII書誌ID
- AA00694073
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- ISSN
- 0021924X
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- IRDB
- CiNii Articles