Adediran S A
Department of Chemistry, University of Ilorin, Nigeria.
Arch Biochem Biophys. 1996 Mar 15;327(2):279-84. doi: 10.1006/abbi.1996.0122.
The kinetics of the decay of compound III of horseradish peroxidase formed from compound II and excess hydrogen peroxide and of the formation of p-670 from this preparation were studied as a function of pH at 25 degrees C and constant ionic strength of 0.11. Compound III undergoes an irreversible formation of p-670 and a slow, spontaneous decay to ferriperoxidase via compound II and the rate of compound III decay is less than that of p-670 formation at all pH values. Both reactions follow pseudo first order kinetics at all pH values. The observed rate constant for compound III decay decreases with increase in pH with a minimum at pH 8.0. Also the observed rate constant for p-670 formation increases with increase in pH with maximum also at pH 8.0. The slow decay of our preparation of compound III and its unique formation of p-670 as compared to oxyperoxidase prepared from ferrous horseradish peroxidase and molecular oxygen (J.B. Wittenberg, R. W. Noble, B.A. Wittenberg, E. Antonini, M. Brunori, and J. Wyman (1967) J. Biol. Chem. 242, 625-34) are discussed in terms of the presence of excess hydrogen peroxide in our preparation. Ferriperoxidase and p-670are formed from compound III in two parallel reactions.
研究了在25℃和恒定离子强度0.11条件下，由化合物II与过量过氧化氢形成的辣根过氧化物酶化合物III的衰变动力学，以及由该制剂形成p - 670的动力学与pH值的关系。化合物III不可逆地形成p - 670，并通过化合物II缓慢自发衰变为高铁过氧化物酶，在所有pH值下，化合物III的衰变速率均小于p - 670的形成速率。在所有pH值下，这两个反应均遵循准一级动力学。观察到的化合物III衰变速率常数随pH值升高而降低，在pH 8.0时达到最小值。同样，观察到的p - 670形成速率常数也随pH值升高而增加，在pH 8.0时达到最大值。与由亚铁辣根过氧化物酶和分子氧制备的氧过氧化物酶相比，我们制备的化合物III衰变缓慢且其独特地形成p - 670（J.B. 维滕贝格、R.W. 诺布尔、B.A. 维滕贝格、E. 安东尼尼、M. 布鲁诺里和J. 怀曼（1967年）《生物化学杂志》242卷，625 - 34页），根据我们的制剂中存在过量过氧化氢进行了讨论。高铁过氧化物酶和p - 670在两个平行反应中由化合物III形成。
