Bacteria can not only encounter carbon monoxide (CO) in their habitats but also produce the gas endogenously. Bacterial respiratory oxidases, thus, represent possible targets for CO. Accordingly, host macrophages were proposed to produce CO and release it into the surrounding microenvironment to sense viable bacteria through a mechanism that in Escherichia (E.) coli was suggested to involve the targeting of a bd-type respiratory oxidase by CO. The aerobic respiratory chain of E. coli possesses three terminal quinol:O2-oxidoreductases: the heme-copper oxidase bo3 and two copper-lacking bd-type oxidases, bd-I and bd-II. Heme-copper and bd-type oxidases differ in the mechanism and efficiency of proton motive force generation and in resistance to oxidative and nitrosative stress, cyanide and hydrogen sulfide. Here, we investigated at varied O2 concentrations the effect of CO gas on the O2 reductase activity of the purified cytochromes bo3, bd-I and bd-II of E. coli. We found that CO, in competition with O2, reversibly inhibits the three enzymes. The inhibition constants Ki for the bo3, bd-I and bd-II oxidases are 2.4 ± 0.3, 0.04 ± 0.01 and 0.2 ± 0.1 μM CO, respectively. Thus, in E. coli, bd-type oxidases are more sensitive to CO inhibition than the heme-copper cytochrome bo3. The possible physiological consequences of this finding are discussed.

中文翻译：

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在大肠杆菌的呼吸链中，细胞色素bd-I和bd-II对一氧化碳的抑制作用比细胞色素bo3更敏感。

细菌不仅会在其生境中遇到一氧化碳（CO），而且还会内生产生气体。因此，细菌呼吸氧化酶代表了CO的可能靶标。因此，提出了宿主巨噬细胞产生CO并将其释放到周围的微环境中，以通过一种在大肠埃希氏菌中涉及靶向于大肠杆菌的机制来感测存活细菌的提议。大肠杆菌的好氧呼吸链具有三个末端的quinol：O2-氧化还原酶：血红铜氧化酶bo3和两个缺铜的bd型氧化酶bd-I和bd-II。血红素铜和bd型氧化酶在质子原动力产生的机理和效率以及对氧化和亚硝化应力，氰化物和硫化氢的耐受性方面有所不同。这里，我们研究了在不同的O2浓度下CO气体对大肠杆菌纯化的细胞色素bo3，bd-I和bd-II的O2还原酶活性的影响。我们发现，CO与O2竞争可逆地抑制这三种酶。bo3，bd-I和bd-II氧化酶的抑制常数Ki分别为2.4±0.3、0.04±0.01和0.2±0.1μMCO。因此，在大肠杆菌中，bd型氧化酶比血红铜细胞色素bo3对CO抑制更敏感。讨论了这一发现的可能的生理后果。分别。因此，在大肠杆菌中，bd型氧化酶比血红铜细胞色素bo3对CO抑制更敏感。讨论了这一发现的可能的生理后果。分别。因此，在大肠杆菌中，bd型氧化酶比血红铜细胞色素bo3对CO抑制更敏感。讨论了这一发现的可能的生理后果。