辣根过氧化物酶化合物I和II对有机金属底物的反应活性。二茂铁氧化的停流动力学研究。

Reactivity of the horseradish peroxidase compounds I and II toward organometallic substrates. A stopped-flow kinetic study of oxidation of ferrocenes.

作者信息

Goral V N, Ryabov A D

机构信息

Department of Chemistry, Moscow State University, Russia.

出版信息

Biochem Mol Biol Int. 1998 Jun;45(1):61-71. doi: 10.1080/15216549800202432.

DOI:10.1080/15216549800202432

PMID:9635130

Abstract

Reactivity of horseradish peroxidase compounds I and II (HRP-I and HRP-II) toward organometallicic substrates, viz water-soluble ferrocenes RFc (R = COOH and CH2NMe2), has been studied at 25 degrees C, pH 6.0 and ionic strength 0.1 M. The second-order rate constants k2 for the reaction of HRP-I with FcCOOH and FcCH2NMe2 equal (1.00 +/- 0.04) x 10(6) and (0.27 +/- 0.01) x 10(6) M-1 s-1, respectively. The values of k3 for the reaction of HRP-II with FcCOOH and FcCH2NMe2 equal (1.1 +/- 0.1) x 10(4) and (0.25 +/- 0.01) x 10(4) M-1 s-1, respectively. The steady-state kinetic study of the HRP-catalyzed oxidation of the ferrocenes by H2O2 under the same conditions gave the second-order rate constants of (0.94 +/- 0.03) x 10(4) and (0.24 +/- 0.06) x 10(4) M-1 s-1 for FcCOOH and FcCH2NMe2, respectively, which are in a good agreement with k3. The results reported here confirm the proposal that the rate-limiting step of the steady-state oxidation of ferrocenes is the electron transfer from the substrate to HRP-II.

摘要

在25℃、pH 6.0和离子强度0.1M的条件下，研究了辣根过氧化物酶化合物I和II（HRP-I和HRP-II）对有机金属底物，即可溶性二茂铁RFc（R = COOH和CH2NMe2）的反应活性。HRP-I与FcCOOH和FcCH2NMe2反应的二级速率常数k2分别为(1.00±0.04)×10(6)和(0.27±0.01)×10(6) M-1 s-1。HRP-II与FcCOOH和FcCH2NMe2反应的k3值分别为(1.1±0.1)×10(4)和(0.25±0.01)×10(4) M-1 s-1。在相同条件下，对HRP催化H2O2氧化二茂铁的稳态动力学研究得出，FcCOOH和FcCH2NMe2的二级速率常数分别为(0.94±0.03)×10(4)和(0.24±0.06)×10(4) M-1 s-1，这与k3值吻合良好。此处报道的结果证实了以下提议：二茂铁稳态氧化的限速步骤是电子从底物转移至HRP-II。