Brown S B, Hatzikonstantinou H, Herries D G
Biochem J. 1978 Sep 15;174(3):901-7. doi: 10.1042/bj1740901.
The oxidation of ferrihaems by H2O2 was studied as a model for haem catabolism. Rates of ferrihaem oxidation were evaluated by using a new computer-based method that measures the loss in catalytic activity of the ferrihaem during oxidation. For protoferrihaem, deuteroferrihaem, coproferrihaem and mesoferrihaem, oxidation proceeded via the monomeric species and no dimer contribution was detectable. The pH-dependence of oxidation was studied in the range 6.5--11. Within experimental error, the data were compatible with an inverse linear dependence on [H+]. This was interpreted in terms of attack by HO2- on monomeric ferrihaem. The specific second-order rate constants for oxidation of monomeric species by HO2- were of the same order of magnitude for all the ferrihaems, and were in the sequence coproferrihaem greater than protoferrihaem greater than mesoferrihaem congruent to deuteroferrihaem. A model is suggested involving formation of a ferrihaem monomerperoxide complex, which may either dissociate with the formation of a peroxidatic intermediate or be involved in an intramolecular oxidation of the ferrihaem. Haem catabolism may occur via the same or a similar intermediate.
以高铁血红素被过氧化氢氧化作为血红素分解代谢的模型进行了研究。高铁血红素氧化速率通过一种新的基于计算机的方法进行评估，该方法测量氧化过程中高铁血红素催化活性的损失。对于原高铁血红素、氘高铁血红素、粪高铁血红素和中高铁血红素，氧化通过单体物种进行，未检测到二聚体的贡献。在6.5 - 11的范围内研究了氧化的pH依赖性。在实验误差范围内，数据与对[H⁺]的反线性依赖性相符。这是根据HO₂⁻对单体高铁血红素的攻击来解释的。HO₂⁻氧化单体物种的特定二级速率常数对于所有高铁血红素都处于相同的数量级，且顺序为粪高铁血红素＞原高铁血红素＞中高铁血红素≈氘高铁血红素。提出了一个模型，涉及高铁血红素单体过氧化物复合物的形成，该复合物可能要么解离形成过氧化物中间体，要么参与高铁血红素的分子内氧化。血红素分解代谢可能通过相同或类似的中间体发生。
