The reactivity of alpha-hydroxyhaem and verdohaem bound to haem oxygenase-1 to dioxygen and sodium dithionite.
The reactivity of alpha-hydroxyhaem and verdohaem bound to haem oxygenase-1 to dioxygen and sodium dithionite.
复制标题
α-羟基血红素和维多血红素与血红素加氧酶-1 结合，生成双氧和连二亚硫酸钠。
DOI：
10.1046/j.1432-1033.2002.03230.x
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
Noguchi,Masato
中科院分区：
文献类型：
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作者：
Sakamoto,Hiroshi;Omata,Yoshiaki;Hayashi,Shunsuke;Harada,Saori;Palmer,Graham;Noguchi,Masato
最近，我们已经证明，在没有外源电子的情况下，与血红素加氧酶-1结合的铁α-羟基血红素可以通过大约等摩尔量的O2转化为亚铁绿血红素[Sakamoto，H.，Omata，Y.，帕尔默，G.，和野口，M。（1999）J.Biol.Chem.274，18196-18200]。与这些结果相反，其他研究声称，转换需要O2和电子。已经报道了α-羟基血红素铁与O2的主要反应产物是铁卟啉阳离子自由基，其可以用连二亚硫酸钠转化为α-羟基血红素铁[Migita，C. T.，藤井，H.，马泰拉湾M.，Takahashi，S.，Zhou，H.，和Yoshida，T.等人（1999）Biochim. Biophys. Acta 1432，203-213]。为了澄清差异的原因，我们比较了反应;即在各种条件下以及根据Migita的程序，α-羟基血红素与绿血红素以及绿血红素与胆绿素。我们发现α-羟基血红素与血红素加氧酶的复合物形成可能很小，并且可能保留大量游离α-羟基血红素，这取决于重构条件;这可能导致对实验结果的误解。我们还发现，亚铁绿血红素似乎是空气敏感的，因此很容易转化为过量O2的进一步氧化物质。最后，我们发现连二亚硫酸盐似乎不适合研究血红素加氧酶反应，因为它将亚铁绿血红素还原为在NADPH-细胞色素P450还原酶驱动的血红素降解系统中未观察到的进一步还原的物质。
Recently we have shown that ferric α‐hydroxyhaem bound to haem oxygenase‐1 can be converted to ferrous verdohaem by approximately an equimolar amount of O2in the absence of exogenous electrons [Sakamoto, H., Omata, Y., Palmer, G., and Noguchi, M. (1999)J. Biol. Chem.274, 18196–18200]. Contrary to those results, other studies have claimed that the conversion requires both O2and an electron. More recently, Migitaet al. have reported that the major reaction product of ferric α‐hydroxyhaem with O2is a ferric porphyrin cation radical that can be converted to ferrous α‐hydroxyhaem with sodium dithionite [Migita, C. T., Fujii, H., Matera, K. M., Takahashi, S., Zhou, H., and Yoshida, T. (1999)Biochim. Biophys. Acta1432, 203–213]. To clarify the reason(s) for the discrepancy, we compared the reactions; i.e. α‐hydroxyhaem to verdohaem and verdohaem to biliverdin, under various conditions as well as according to the procedures of Migita. We find that complex formation of α‐hydroxyhaem with haem oxygenase may be small and a substantial amount of free α‐hydroxyhaem may remain, depending on the reconstitution conditions; this could lead to a misinterpretation of the experimental results. We also find that ferrous verdohaem appears to be air‐sensitive and is therefore easily converted to a further oxidized species with excess O2. Finally, we find that dithionite seems to be inappropriate for investigating the haem oxygenase reaction, because it reduces ferrous verdohaem to a further reduced species that has not been seen in the haem degradation system driven by NADPH‐cytochrome P450 reductase.