过氧化氢酶模型系统。由中高铁血红素、氘高铁血红素、粪高铁血红素和血高铁血红素催化的过氧化氢分解。
Catalase model systems. Decomposition of hydrogen peroxide catalysed by mesoferrihaem, deuteroferrihaem, coproferrihaem and haematoferrihaem.
作者信息
Hatzikonstantinou H, Brown S B
出版信息
Biochem J. 1978 Sep 15;174(3):893-900. doi: 10.1042/bj1740893.
The catalytic decomposition of H2O2 by deuteroferrihaem, mesoferrihaem, coproferrihaem and haematoferrihaem was studied as a model for the mechanism of action of catalase. For haematoferrihaem, anomalous but reproducible results were obtained, which could not be adequately explained. For each of the other ferrihaems studied, both monomeric and dimeric species catalysed decomposition, although the activity of monomer (aM) was much greater than that of dimer (aD). The pH variation of aD in the range 6.5--11 was consistent with an inverse dependence on [H+]1/2. The molecular mechanism whereby such a dependence could be achieved is not apparent. A study of the pH-dependence of aM in the range 6.5--11 revealed a linear inverse relationship with [H+]. This is interpreted in terms of attack by HO2- on ferrihaem monomer. The specific pH-independent rate constants for this reaction were in the order coproferrihaem greater than protoferrihaem greater than or equal to mesoferrihaem congruent to deuteroferrihaem. The order of magnitude of these rate constants is the same as that for catalysis by Fe(H2O)63+ and the second-order rate constant for decomposition of H2O2 by catalase. The implications on the mechanism of action of catalase are discussed.
研究了氘代高铁血红素、中高铁血红素、粪高铁血红素和血高铁血红素对过氧化氢的催化分解作用，以此作为过氧化氢酶作用机制的模型。对于血高铁血红素，得到了异常但可重复的结果，无法给出充分解释。对于所研究的其他每种高铁血红素，单体和二聚体都能催化分解，尽管单体（aM）的活性远大于二聚体（aD）。aD在6.5 - 11范围内随pH的变化与对[H⁺]¹/²呈反比关系一致。实现这种依赖性的分子机制并不明显。对aM在6.5 - 11范围内的pH依赖性研究揭示了其与[H⁺]呈线性反比关系。这是根据HO₂⁻对高铁血红素单体的攻击来解释的。该反应的特定pH无关速率常数的顺序为粪高铁血红素大于原高铁血红素大于或等于中高铁血红素约等于氘代高铁血红素。这些速率常数的量级与Fe(H₂O)₆³⁺催化以及过氧化氢酶催化过氧化氢分解的二级速率常数相同。讨论了其对过氧化氢酶作用机制的影响。
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