Mechanism of Superoxide Dismutase-Like Activity of Fe(II)and Fe(III) Complexes of Tetrakis-N,N,N′,N′(2-pyridylmethyl)ethylenediamine
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- タイトル別名
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- Mechanism of Superoxide Dismutase-Like Activity of Fe(II) and Fe(III) Complexes of Tetrakis-N,N,N',N'(2-pyridylmethyl)ethylenediamine.
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The superoxide dismutase (SOD) activity of iron(II) tetrakis-N, N, N', N' (2-pyridylmethyl)ethylenediamine complex (Fe-TPEN) was reexamined using a pulse radiolysis mehtod. In our previous study (J. Biol. Chem., 264, 9243-9249 (1989)), we reportd that this complex has a potent SOD activity in a cyt. c (cytochrome c)-based system (IC50=0.8 μM) and protects E. coli cells against paraquat toxicity . The present pulse radiolysis experiment revealed that Fe(II)TPEN reacts stoichiometrically with superoxide to form Fe(III)TPEN with a second-order rate constant of 3.9×106M-1s-1 at pH 7.1, but superoxide did not reduce Fe(III)TPEN to Fe(II)TPEN. The reaction of Fe(III)TPEN and superoxide was biphasic. In the fast reaction, an adduct (Fe(III)TPEN-superoxide complex) was formed at the second-order rate constant of 8.5×105M-1S-1 at pH 7.4. In the slow one, the adduct reacted with another moleculre of the adduct, regenerating Fe(III)TPEN. In the cyt. c method with catalase, this Fe(III)TPEN-superoxide complex showed cyt.c oxidation activity, which had led to overstimation of its SOD activity. Based on the titration data, the main species of complex in aqueous media at neutral pH was indicated to be Fe(III)TPEN(OH-). A spectral chagne after the reduction with hydrated electron indicates that the OH- ion coordinates directly to Fe(III) by displacing one of the pyridine rings. The X-ray analysis of [Fe(II)TPEN]SO4 supported this structure. From the above results we propose a novel reaction mechanism of FeTPEN and superoxide which resembles a proton catalyzed dismuting process, involving Fe(III)TPEN-superoxide complex.
収録刊行物
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- ＣＨＥＭＩＣＡＬ ＆ ＰＨＡＲＭＡＣＥＵＴＩＣＡＬ ＢＵＬＬＥＴＩＮ
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ＣＨＥＭＩＣＡＬ ＆ ＰＨＡＲＭＡＣＥＵＴＩＣＡＬ ＢＵＬＬＥＴＩＮ 48 (2), 223-230, 2000
公益社団法人 日本薬学会
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詳細情報 詳細情報について
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- CRID
- 1390001204162579456
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- NII論文ID
- 130003948053
- 110003635433
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- NII書誌ID
- AA00602100
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- ISSN
- 13475223
- 00092363
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- NDL書誌ID
- 4978560
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- PubMed
- 10705509
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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
- NDL
- Crossref
- PubMed
- CiNii Articles
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- 使用不可