Ho P S, Hoffman B M, Solomon N, Kang C H, Margoliash E
Biochemistry. 1984 Aug 28;23(18):4122-8. doi: 10.1021/bi00313a017.
The oxidation of ferric cytochrome c peroxidase by hydrogen peroxide yields a product, compound ES [Yonetani, T., Schleyer, H., Chance, B., & Ehrenberg, A. (1967) in Hemes and Hemoproteins (Chance, B., Estabrook, R. W., & Yonetani, T., Eds.) p 293, Academic Press, New York], containing an oxyferryl heme and a protein free radical [Dolphin, D., Forman, A., Borg, D. C., Fajer, J., & Felton, R. H. (1971) Proc. Natl. Acad. Sci. U.S.A. 68, 614-618]. The same oxidant takes the ferrous form of the enzyme to a stable Fe(IV) peroxidase [Ho, P. S., Hoffman, B. M., Kang, C. H., & Margoliash, E. (1983) J. Biol. Chem. 258, 4356-4363]. It is 1 equiv more highly oxidized than the ferric protein, contains the oxyferryl heme, but leaves the radical site unoxidized. Addition of sodium fluoride to Fe(IV) peroxidase gives a product with an optical spectrum similar to that of the fluoride complex of the ferric enzyme. However, reductive titration and electron paramagnetic resonance (EPR) data demonstrate that the oxidizing equivalent has not been lost but rather transferred to the radical site. The EPR spectrum for the radical species in the presence of Fe(III) heme is identical with that of compound ES, indicating that the unusual characteristics of the radical EPR signal do not result from coupling to the heme site. By stopped-flow measurements, the oxidizing equivalent transfer process between heme and radical site is first order, with a rate constant of 0.115 s-1 at room temperature, which is independent of either ligand or protein concentration.(ABSTRACT TRUNCATED AT 250 WORDS)
过氧化氢将高铁细胞色素c过氧化物酶氧化会产生一种产物，即化合物ES [米谷谷，T.，施莱尔，H.，钱斯，B.，& 埃伦贝格，A.（1967年），载于《血红素与血红蛋白》（钱斯，B.，埃斯塔布鲁克，R. W.，& 米谷谷，T. 编），第293页，学术出版社，纽约]，它含有一个氧合高铁血红素和一个蛋白质自由基 [多尔芬，D.，福尔曼，A.，博格，D. C.，法杰尔，J.，& 费尔顿，R. H.（1971年），《美国国家科学院院刊》68，614 - 618]。相同的氧化剂将酶的亚铁形式氧化为稳定的Fe(IV)过氧化物酶 [何，P. S.，霍夫曼，B. M.，康，C. H.，& 马戈利阿什，E.（1983年），《生物化学杂志》258，4356 - 4363]。它比高铁蛋白的氧化态高1当量，含有氧合高铁血红素，但自由基位点未被氧化。向Fe(IV)过氧化物酶中添加氟化钠会产生一种产物，其光谱类似于高铁酶的氟化物复合物的光谱。然而，还原滴定和电子顺磁共振（EPR）数据表明，氧化当量并未丢失，而是转移到了自由基位点。在存在Fe(III)血红素的情况下，自由基物种的EPR光谱与化合物ES的相同，这表明自由基EPR信号的异常特征并非由与血红素位点的耦合引起。通过停流测量，血红素和自由基位点之间的氧化当量转移过程是一级反应，在室温下速率常数为0.115 s-1，这与配体或蛋白质浓度无关。（摘要截短于250字）
