微过氧化物酶-11的自杀性过氧化物失活：一项动力学研究。

Suicide-peroxide inactivation of microperoxidase-11: a kinetic study.

作者信息

Khosraneh M, Mahmoudi A, Rahimi H, Nazari K, Moosavi-Movahedi A A

机构信息

Chemistry Department, Karaj Islamic Azad University, Karaj, Iran.

出版信息

J Enzyme Inhib Med Chem. 2007 Dec;22(6):677-84. doi: 10.1080/14756360701270683.

DOI:10.1080/14756360701270683

PMID:18237019

Abstract

The kinetics of microperoxidase-11 (MP-11) in the oxidation reaction of guaiacol (AH) by hydrogen peroxide was studied, taking into account the inactivation of enzyme during reaction by its suicide substrate, H2O2. Concentrations of substrates were so selected that: 1) the reaction was first-order in relation to benign substrate, AH and 2) high ratio of suicide substrate to the benign substrate, [H2O2] >> [AH]. Validation and reliability of the obtained kinetic equations were evaluated in various nonlinear and linear forms. Fitting of experimental data into the obtained integrated equation showed a close match between the kinetic model and the experimental results. Indeed, a similar mechanism to horseradish peroxidase was found for the suicide-peroxide inactivation of MP-11. Kinetic parameters of inactivation including the intact activity of MP-11, alphai, and the apparent inactivation rate constant, ki, were obtained as 0.282 +/- 0.006 min(-1) and 0.497 +/- 0.013(-1) min at [H2O2] = 1.0 mM, 27 degrees C, phosphate buffer 5.0 mM, pH = 7.0. Results showed that inactivation of microperoxidase as a peroxidase model enzyme can occur even at low concentrations of hydrogen peroxide (0.4 mM).

摘要

研究了微过氧化物酶-11（MP-11）在过氧化氢氧化愈创木酚（AH）反应中的动力学，同时考虑到反应过程中自杀底物过氧化氢导致酶失活的情况。底物浓度的选择满足以下条件：1）反应对良性底物AH为一级反应；2）自杀底物与良性底物的比例较高，即[H₂O₂] >> [AH]。通过各种非线性和线性形式评估所获得动力学方程的有效性和可靠性。将实验数据拟合到所得积分方程中，结果表明动力学模型与实验结果吻合良好。实际上，发现MP-11的自杀性过氧化物失活机制与辣根过氧化物酶类似。在[H₂O₂] = 1.0 mM、27℃、5.0 mM磷酸盐缓冲液、pH = 7.0条件下，获得的失活动力学参数包括MP-11的完整活性αi和表观失活速率常数ki，分别为0.282±0.006 min⁻¹和0.497±0.013 min⁻¹。结果表明，即使在低浓度过氧化氢（0.4 mM）下，作为过氧化物酶模型酶的微过氧化物酶也会发生失活。