Baynton K J, Bewtra J K, Biswas N, Taylor K E
Department of Chemistry and Biochemistry, University of Windsor, Ont., Canada.
Biochim Biophys Acta. 1994 Jun 12;1206(2):272-8. doi: 10.1016/0167-4838(94)90218-6.
Inactivation of horseradish peroxidase (HRP) was examined in the presence of hydrogen peroxide alone and in the presence of hydrogen peroxide plus phenol. HRP is inactivated upon exposure to hydrogen peroxide (H2O2) by the combination of two possible pathways, dependent upon hydrogen peroxide concentration. At low H2O2 concentrations (below 1.0 mM in the absence of phenol), inactivation is predominantly reversible, resulting from the formation and accumulation of catalytically inert intermediate compound III. As H2O2 concentrations increase, an irreversible mechanism-based inactivation process becomes predominant. The overall inactivation comprised of both processes exhibits a second-order inactivation rate constant (kapp) of 0.023 +/- 0.005 M-1 s-1 at pH 7.4 and 25 degrees C. In the presence of both hydrogen peroxide fixed at 0.5 mM and phenol, HRP was inactivated in an irreversible, time- and phenol concentration-dependent process, also mechanism-based, with a kapp of 0.019 +/- 0.004 M-1 s-1.
分别在仅存在过氧化氢以及过氧化氢与苯酚同时存在的情况下，对辣根过氧化物酶（HRP）的失活情况进行了研究。HRP暴露于过氧化氢（H₂O₂）时，会通过两种可能的途径失活，这取决于过氧化氢的浓度。在低H₂O₂浓度下（在不存在苯酚时低于1.0 mM），失活主要是可逆的，这是由催化惰性中间体化合物III的形成和积累导致的。随着H₂O₂浓度的增加，基于机制的不可逆失活过程变得占主导地位。由这两个过程组成的总体失活在pH 7.4和25℃时表现出二级失活速率常数（kapp）为0.023±0.005 M⁻¹ s⁻¹。在固定为0.5 mM的过氧化氢和苯酚同时存在的情况下，HRP通过一个不可逆的、与时间和苯酚浓度相关的过程失活，该过程也是基于机制的，kapp为0.019±0.004 M⁻¹ s⁻¹。
