Pérez-Gilabert M, Sánchez-Ferrer A, García-Carmona F
Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universidad de Murcia, Spain.
Biochim Biophys Acta. 1994 Sep 15;1214(2):203-8. doi: 10.1016/0005-2760(94)90045-0.
The hydroperoxidase activity of soybean lipoxygenase, a non-heme protein, oxidizes chlorpromazine using H2O2 at acidic pHs ranging from 3.0 to 4.0. The enzyme is assayed at pH 3.5, at which the half-life is 2 h (lower pHs cause higher inactivation rates). This oxidation is enzymatical since boiled enzyme or even iron ions both with H2O2 failed to produce any increase in absorbance. In addition, the concentration of CPZ radical cation formed and the concomitant enzyme activity directly depends on the enzyme concentration up to 0.23 microM. The Vmax value is 125 mumol/min per mg protein and the Km for chlorpromazine and H2O2 are 2.1 mM and 0.25 mM, respectively. Similar results were obtained when linoleic acid hydroperoxide was used instead of H2O2 with a Km value of 95 microM. The radical cation obtained in the oxidation of chlorpromazine by lipoxygenase decays by a disproportionation reaction. This permits to consider the overall reaction as a sum of an enzymatic reaction coupled with a chemical second order reaction with substrate regeneration, similar to those produced by peroxidases from different sources.
大豆脂氧合酶是一种非血红素蛋白，在pH值为3.0至4.0的酸性条件下，其氢过氧化物酶活性利用H2O2氧化氯丙嗪。该酶在pH 3.5条件下进行测定，此时半衰期为2小时（较低的pH值会导致更高的失活速率）。这种氧化是酶促反应，因为煮沸的酶或铁离子与H2O2一起都不会使吸光度增加。此外，形成的CPZ自由基阳离子的浓度和伴随的酶活性直接取决于酶浓度，最高可达0.23微摩尔。Vmax值为每毫克蛋白质125微摩尔/分钟，氯丙嗪和H2O2的Km值分别为2.1毫摩尔和0.25毫摩尔。当使用亚油酸氢过氧化物代替H2O2时，也获得了类似的结果，其Km值为95微摩尔。脂氧合酶氧化氯丙嗪过程中得到的自由基阳离子通过歧化反应衰变。这使得可以将整个反应视为一个酶促反应与一个底物再生的化学二级反应的总和，类似于不同来源的过氧化物酶所产生的反应。
