Escobar J A, Rubio M A, Lissi E A
Departamento Ciencias Químicas, Universidad de Santiago de Chile.
Free Radic Biol Med. 1996;20(3):285-90. doi: 10.1016/0891-5849(95)02037-3.
Both superoxide dismutase and catalase are readily deactivated by singlet oxygen and by the radicals produced in the pyrolysis of 2,2'-azo-bis-(2-amidinpropano) under aerobic conditions. The rate constant for the loss of enzymatic activity induced by singlet oxygen are 3.9 x 10(7) and 2.5 x 10(7) M-1 sec-1 for SOD and catalase, respectively. The similarity between these values implies that in systems where SOD and catalase are exposed to similar singlet oxygen concentrations, it can be expected a parallel inactivation of both enzymes. The inactivation of both enzymes by the radicals produced by 2,2'-azo-bis-(2-amidinopropane) pyrolysis under aerobic conditions follows a first-order kinetics at low enzyme concentrations and a zero-order kinetics at higher concentrations. Although at low enzymatic concentrations the rate of inactivation of both enzymes is similar, this results from a compensation of effects because there are wide differences in the reactivity of both enzymes towards peroxyalkyl radicals. Catalase is considerably more reactive, but a large number of protein/radical reactive interactions are needed to inactivate one enzyme. On the other hand, the reactivity of SOD is smaller, but the average enzyme activity decreases by nearly 20% in each SOD/radical reactive interaction.
超氧化物歧化酶和过氧化氢酶在有氧条件下都很容易被单线态氧以及2,2'-偶氮双-(2-脒基丙烷)热解产生的自由基失活。单线态氧诱导的酶活性丧失的速率常数，超氧化物歧化酶（SOD）和过氧化氢酶分别为3.9×10⁷和2.5×10⁷ M⁻¹ s⁻¹。这些值之间的相似性表明，在SOD和过氧化氢酶暴露于相似单线态氧浓度的系统中，可以预期这两种酶会同时失活。在有氧条件下，2,2'-偶氮双-(2-脒基丙烷)热解产生的自由基对这两种酶的失活作用，在低酶浓度下遵循一级动力学，在高浓度下遵循零级动力学。虽然在低酶浓度下两种酶的失活速率相似，但这是由于效应的补偿，因为两种酶对过氧烷基自由基的反应性存在很大差异。过氧化氢酶的反应性要强得多，但使一种酶失活需要大量的蛋白质/自由基反应相互作用。另一方面，SOD的反应性较小，但在每次SOD/自由基反应相互作用中，平均酶活性会降低近20%。
