Abstract：
Carbon monoxide (CO) plays a multifaceted role in the physiology of organisms, from poison to signaling molecule. Heme proteins, including terminal oxidases, are plausible CO targets. Three quinol oxidases terminate the branched aerobic respiratory chain of Escherichia coli. These are the heme‑copper cytochrome bo3 and two copper-lacking bd-type cytochromes, bd-I and bd-II. All three enzymes generate a proton motive force during the four-electron oxygen reduction reaction that is used for ATP production. The bd-type oxidases also contribute to mechanisms of bacterial defense against various types of stresses. Here we report that in E. coli cells, at the enzyme concentrations tested, cytochrome bd-I is much more resistant to inhibition by CO than cytochrome bd-II and cytochrome bo3. The apparent half-maximal inhibitory concentration values, IC50, for inhibition of O2 consumption of the membrane-bound bd-II and bo3 oxidases by CO at ~150 μM O2 were estimated to be 187.1 ± 11.1 and 183.3 ± 13.5 μM CO, respectively. Under the same conditions, the maximum inhibition observed with the membrane-bound cytochrome bd-I was 20 ± 10% at ~200 μM CO.
摘要：
一氧化碳（CO）在生物体的生理学中起着多方面的作用，从毒药到信号分子。血红素蛋白,包括末端氧化酶，是合理的CO目标。三种喹啉氧化酶终止了大肠杆菌的分支需氧呼吸链。这些是血红素铜细胞色素bo3和两个缺乏铜的bd型细胞色素，BD-I和BD-II.所有三种酶在用于ATP生产的四电子氧还原反应期间产生质子原动力。bd型氧化酶还有助于细菌防御各种类型的胁迫的机制。在这里，我们报告了在大肠杆菌细胞中，在测试的酶浓度下，细胞色素bd-I比细胞色素bd-II和细胞色素bo3更能抵抗CO的抑制。表观半最大抑制浓度值，在〜150μMO2时，对于CO抑制膜结合bd-II和bo3氧化酶的O2消耗的IC50估计为187.1±11.1和183.3±13.5μMCO，分别。在同样的条件下,在约200μM的CO下，膜结合的细胞色素bd-I观察到的最大抑制作用为20±10％。
