Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa
Enzymatic Characterization and In Vivo Function of Five Terminal Oxidases in Pseudomonas aeruginosa
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DOI：
10.1128/jb.02176-14
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发表时间：
2014-12-01
影响因子：
3.2
通讯作者：
Ishii, Masaharu
中科院分区：
文献类型：
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作者：
Arai, Hiroyuki;Kawakami, Takuro;Ishii, Masaharu
普遍存在的条件致病菌铜绿假单胞菌具有五种需氧末端氧化酶：bo（3）-型醌醇氧化酶（Cyo）、氰化物不敏感氧化酶（CIO）、aa（3）-型细胞色素c氧化酶（aa（3））和两种cbb（3）-型细胞色素c氧化酶（cbb（3）-1和cbb（3）-2）。这些末端氧化酶在不同的生长条件下受到不同的调节，并被认为有助于这种微生物在各种各样的环境小生境中的生存。在这里，我们构建了多个铜绿假单胞菌突变株，只表达一种需氧末端氧化酶，以研究每种酶的酶特性和体内功能。Cyo、CIO和aa（3）对氧的Km值相似，比cbb（3）-1和cbb（3）-2的Km值高1个数量级，表明Cyo、CIO和aa（3）是低亲和力酶，而cbb（3）-1和cbb（3）-2是高亲和力酶。虽然cbb（3）-1和cbb（3）-2对氧浓度的反应表现出不同的表达模式，但它们对氧的Km值相似。在正常生长条件下，cbb（3）-1和cbb（3）-2都利用细胞色素c（4）作为主要的电子供体。由cbb（3）-1和cbb（3）-2终止的电子传递链以相似的效率产生穿过细胞膜的质子梯度。aa（3）的电子传递链质子转运效率最高，而CIO的电子传递链质子转运效率最低。本文报道的末端氧化酶的酶学性质与其调控模式部分一致，并可能解释铜绿假单胞菌的环境适应性和多功能性。
The ubiquitous opportunistic pathogen Pseudomonas aeruginosa has five aerobic terminal oxidases: bo(3)-type quinol oxidase (Cyo), cyanide-insensitive oxidase (CIO), aa(3)-type cytochrome c oxidase (aa(3)), and two cbb(3)-type cytochrome c oxidases (cbb(3)-1 and cbb(3)-2). These terminal oxidases are differentially regulated under various growth conditions and are thought to contribute to the survival of this microorganism in a wide variety of environmental niches. Here, we constructed multiple mutant strains of P. aeruginosa that express only one aerobic terminal oxidase to investigate the enzymatic characteristics and in vivo function of each enzyme. The K-m values of Cyo, CIO, and aa(3) for oxygen were similar and were 1 order of magnitude higher than those of cbb(3)-1 and cbb(3)-2, indicating that Cyo, CIO, and aa(3) are low-affinity enzymes and that cbb(3)-1 and cbb(3)-2 are high-affinity enzymes. Although cbb(3)-1 and cbb(3)-2 exhibited different expression patterns in response to oxygen concentration, they had similar Km values for oxygen. Both cbb(3)-1 and cbb(3)-2 utilized cytochrome c(4) as the main electron donor under normal growth conditions. The electron transport chains terminated by cbb(3)-1 and cbb(3)-2 generate a proton gradient across the cell membrane with similar efficiencies. The electron transport chain of aa(3) had the highest proton translocation efficiency, whereas that of CIO had the lowest efficiency. The enzymatic properties of the terminal oxidases reported here are partially in agreement with their regulatory patterns and may explain the environmental adaptability and versatility of P. aeruginosa.