A new look at the biosynthesis of 4-hydroxy-2-alkylquinolines in Pseudomonas aeruginosa

该研究计划旨在破译4-羟基-2-烷基喹啉（HAQs）的生物合成，HAQs是一类参与“群体感应”的化合物，这是细菌之间的一种交流模式。HAQ由铜绿假单胞菌产生，铜绿假单胞菌是一种机会致病菌，其使用群体感应来控制毒力因子的表达。 抑制该细菌中HAQs的产生导致其毒力的显著降低。然而，HAQ的生物合成尚未完全阐明，为了有效地对抗这些信号化合物的产生，重要的是找到参与其生物合成的酶和中间体的作用。虽然我们知道来自pqsABCDE操纵子的基因是HAQ合成所必需的，但它们编码的酶的作用仅部分已知。自20世纪50年代中期发现HAQ以来，人们认为3-酮脂肪酸是HAQ生物合成中的中间体。在初步实验中，我们发现，脂肪酸而不是3-酮脂肪酸是所涉及的中间体。这种模式的变化带来了新的光的作用，一些酶在这一生物合成途径中的牵连。因此，我们现在认为HAQ生物合成是一个两步过程，其中PqsD负责邻氨基苯甲酸与丙二酸酯衍生物的偶联以产生2-氨基-苯甲酰乙酸，并且该中间体与脂肪酸反应以产生HAQ。我们将通过纯化我们假设参与第二步的酶PqsB和PqsC来证实这一假设。我们以前还发现了一系列似乎特异性抑制PqsC和/或PqsB的化合物。一旦了解了这两种酶的具体作用，我们将研究这些化合物对它们的抑制作用。我们将寻找这些化合物的类似物，它们可能比我们现有的化合物更活跃。我们的长期目标是开发一种新的方法，通过靶向铜绿假单胞菌的群体感应来抑制其感染，这将是使用抗生素的替代方法，这种方法会导致耐药性的发展。

This research program is aimed at deciphering the biosynthesis of 4-hydroxy-2-alkylquinolines (HAQs), which are a class of compounds that are involved in "Quorum Sensing", a mode of communication between bacteria. HAQs are produced by Pseudomonas aeruginosa, an opportunistic pathogen that uses Quorum Sensing to control the expression of virulence factors. Inhibiting the production of HAQs in this bacterium leads to a considerable decrease of its virulence. However, the biosynthesis of HAQs is not fully elucidated and in order to efficiently counter the production of these signaling compounds, it is important to find the role of the enzymes and intermediates involved in their biosynthesis. Although we know that the genes from the pqsABCDE operon are required for HAQ synthesis, the role of the enzymes that they encode is only partially known. Since the discovery of HAQs in the mid 1950s, it was believed that 3-ketofatty acids are intermediates in the biosynthesis of HAQs. In preliminary experiments, we discovered that instead of 3-ketofatty acids, fatty acids were the intermediates involved. This paradigm change brings new light on the role of some of the enzymes implicated in this biosynthesis pathway. Thus we now think that HAQ biosynthesis is a two-step process in which PqsD is responsible for the coupling of anthranilic acid with a malonate derivative to produce 2-amino-benzoylacetic acid and that this intermediate reacts with a fatty acid to produce HAQs. We will confirm this hypothesis by purifying the enzymes PqsB and PqsC that we hypothesize are involved in this second step. We also previously found a series of compounds that seem to inhibit specifically PqsC and/or PqsB. Once the specific role these two enzymes will be understood, we will study their inhibition by these compounds. We will look for analogs of these compounds that might be more active than those we already have. Our long-term goal is to develop a new way to inhibit infections by P. aeruginosa by targeting their quorum sensing, which would be an alternative to the use of antibiotics, an approach which leads to the development of resistance.