Institute for Molecular Microbiology and Biotechnology, University of Münster, Münster, Germany.
Institute for Molecular Microbiology and Biotechnology, University of Münster, Münster, Germany
Appl Environ Microbiol. 2021 Feb 26;87(6). doi: 10.1128/AEM.02241-20.
The multiple biological activities of 2-alkylquinolones (AQs) are crucial for virulence of , conferring advantages during infection and in polymicrobial communities. Whereas 2-heptyl-3-hydroxyquinolin-4(1)-one (the " quinolone signal" [PQS]) is an important quorum sensing signal molecule, 2-alkyl-1-hydroxyquinolin-4(1)-ones (also known as 2-alkyl-4-hydroxyquinoline -oxides [AQNOs]) are antibiotics inhibiting respiration. Hydroxylation of the PQS precursor 2-heptylquinolin-4(1)-one (HHQ) by the signal synthase PqsH boosts AQ quorum sensing. Remarkably, the same reaction, catalyzed by the ortholog AqdB, is used by to initiate degradation of AQs. The antibiotic 2-heptyl-1-hydroxyquinolin-4(1)-one (HQNO) is hydroxylated by to the less toxic derivative PQS--oxide (PQS-NO), a reaction probably also catalyzed by a PqsH/AqdB ortholog. In this study, we provide a comparative analysis of four AQ 3-monooxygenases of different organisms. Due to the major impact of AQ/AQNO 3-hydroxylation on the biological activities of the compounds, we surmised adaptations on the enzymatic and/or physiological level to serve either the producer or target organisms. Our results indicate that all enzymes share similar features and are incapable of discriminating between AQs and AQNOs. PQS-NO, hence, occurs as a native metabolite of although the unfavorable AQNO 3-hydroxylation is minimized by export as shown for HQNO, involving at least one multidrug efflux pump. Moreover, is capable of degrading the AQNO heterocycle by concerted action of AqdB and dioxygenase AqdC. However, and orthologs disfavor AQNOs despite their higher toxicity, suggesting that catalytic constraints restrict evolutionary adaptation and lead to the preference of non--oxide substrates by AQ 3-monooxygenases., , and are major players in bacterial chronic infections and particularly common colonizers of cystic fibrosis (CF) lung tissue. Whereas is an early onset pathogen in CF, establishes at later stages. occurs at all stages but has a lower epidemiological incidence. The dynamics of how these pathogens interact can affect survival and therapeutic success. 2-Alkylquinolone (AQ) and 2-alkylhydroxyquinoline -oxide (AQNO) production is a major factor of virulence. The 3-position of the AQ scaffold is critical, both for attenuation of AQ toxicity or degradation by competitors, as well as for full unfolding of quorum sensing. Despite lacking signaling functionality, AQNOs have the strongest impact on suppression of Gram-positives. Because evidence for 3-hydroxylation of AQNOs has been reported, it is desirable to understand the extent by which AQ 3-monooxygenases contribute to manipulation of AQ/AQNO equilibrium, resistance, and degradation.
2-烷基喹诺酮（AQs）的多种生物学活性对 的毒力至关重要，使其在感染和多微生物群落中具有优势。虽然 2-庚基-3-羟基喹啉-4（1）-酮（“喹诺酮信号”[PQS]）是一种重要的群体感应信号分子，但 2-烷基-1-羟基喹啉-4（1）-酮（也称为 2-烷基-4-羟基喹啉 -氧化物[AQNOs]）是抑制呼吸的抗生素。信号合酶 PqsH 对 PQS 前体 2-庚基喹啉-4（1）-酮（HHQ）的羟化作用增强了 AQ 群体感应。值得注意的是，相同的反应，由同源物 AqdB 催化，被 用来启动 AQs 的降解。抗生素 2-庚基-1-羟基喹啉-4（1）-酮（HQNO）被 羟化为毒性较低的衍生物 PQS--氧化物（PQS-NO），该反应可能也由 PqsH/AqdB 同源物催化。在这项研究中，我们对来自不同生物体的四种 AQ 3-单加氧酶进行了比较分析。由于 AQ/AQNO 3-羟化对化合物生物学活性的重大影响，我们推测在酶和/或生理水平上存在适应，以服务于产生者或靶标生物体。我们的结果表明，所有酶都具有相似的特征，并且不能区分 AQs 和 AQNOs。因此，PQS-NO 作为 的天然代谢物存在，尽管 HQNO 的不利 AQNO 3-羟化作用通过出口最小化，至少涉及一种多药外排泵。此外， 能够通过 AqdB 和双加氧酶 AqdC 的协同作用降解 AQNO 杂环。然而，尽管 AQNOs 毒性更高，但 和 同源物却不喜欢 AQNOs，这表明催化约束限制了进化适应，并导致 AQ 3-单加氧酶优先选择非 -氧化物底物。 、 和 是细菌慢性感染的主要参与者，特别是囊性纤维化（CF）肺部组织的常见定植者。 是 CF 中早期发病的病原体， 则在后期定植。 存在于所有阶段，但流行病学发病率较低。这些病原体相互作用的动态变化会影响生存和治疗效果。2-烷基喹诺酮（AQ）和 2-烷基羟喹啉 -氧化物（AQNO）的产生是 的主要毒力因素。AQ 支架的 3 位对于 AQ 毒性的衰减或被竞争者降解都至关重要，同时对于群体感应的完全展开也至关重要。尽管缺乏信号功能，但 AQNOs 对抑制革兰氏阳性菌的影响最大。由于已经报道了 AQNOs 的 3-羟化作用，因此了解 AQ 3-单加氧酶在操纵 AQ/AQNO 平衡、抗性和降解方面的贡献程度是很有必要的。
