Sousa Filipa L, Veríssimo Andreia F, Baptista António M, Soulimane Tewfik, Teixeira Miguel, Pereira Manuela M
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, 2781-901 Oeiras, Portugal.
Biophys J. 2008 Mar 15;94(6):2434-41. doi: 10.1529/biophysj.107.122614. Epub 2007 Dec 7.
A comprehensive study of the thermodynamic redox behavior of the hemes of the ba3 enzyme from Thermus thermophilus, a B-type heme-copper oxygen reductase, is presented. This enzyme, in contrast to those having a single type of heme, allows the B- and A-type hemes to be monitored separately by visible spectroscopy and the reduction potential of each heme to be determined unequivocally. The relative order of the midpoint reduction potentials of each center changed in the pH range from 6 to 8.4, and both hemes present a significant redox-Bohr effect. For instance, at pH 7, the midpoint reduction potentials of the hemes B and A3 are 213 mV and 285 mV, respectively, whereas at pH 8.4, the order is reversed: 246 mV for heme B and 199 mV for heme A3. The existence of redox anticooperativity was established by introducing a redox interaction parameter in a model of pairwise interacting redox centers.
本文对嗜热栖热菌的Ba3酶（一种B型血红素-铜氧还原酶）血红素的热力学氧化还原行为进行了全面研究。与具有单一类型血红素的酶不同，该酶可通过可见光谱法分别监测B型和A型血红素，并明确测定每种血红素的还原电位。每个中心的中点还原电位的相对顺序在pH值6至8.4范围内发生变化，且两种血红素均呈现出显著的氧化还原玻尔效应。例如，在pH 7时，血红素B和A3的中点还原电位分别为213 mV和285 mV，而在pH 8.4时，顺序相反：血红素B为246 mV，血红素A3为199 mV。通过在成对相互作用的氧化还原中心模型中引入氧化还原相互作用参数，确定了氧化还原反协同性的存在。
