Microbial Biology, Ruhr University Bochum, Bochum, Germany.
Microbial Biology, Ruhr University Bochum, Bochum, Germany.
Biochim Biophys Acta Mol Cell Biol Lipids. 2021 Jul;1866(7):158926. doi: 10.1016/j.bbalip.2021.158926. Epub 2021 Mar 22.
Bacterial membranes are primarily composed of phosphatidylethanolamine (PE), phosphatidylglycerol (PG) and cardiolipin (CL). In the canonical PE biosynthesis pathway, phosphatidylserine (PS) is decarboxylated by the Psd enzyme. CL formation typically depends on CL synthases (Cls) using two PG molecules as substrates. Only few bacteria produce phosphatidylcholine (PC), the hallmark of eukaryotic membranes. Most of these bacteria use phospholipid N-methyltransferases to successively methylate PE to PC and/or a PC synthase (Pcs) to catalyze the condensation of choline and CDP-diacylglycerol (CDP-DAG) to PC. In this study, we show that membranes of Pseudomonas species able to interact with eukaryotes contain PE, PG, CL and PC. More specifically, we report on PC formation and a poorly characterized CL biosynthetic pathway in the plant pathogen P. syringae pv. tomato. It encodes a Pcs enzyme responsible for choline-dependent PC biosynthesis. CL formation is catalyzed by a promiscuous phospholipase D (PLD)-type enzyme (PSPTO_0095) that we characterized in vivo and in vitro. Like typical bacterial CL biosynthesis enzymes, it uses PE and PG for CL production. This enzyme is also able to convert PE and glycerol to PG, which is then combined with another PE molecule to synthesize CL. In addition, the enzyme is capable of converting ethanolamine or methylated derivatives into the corresponding phospholipids such as PE both in P. syringae and in E. coli. It can also hydrolyze CDP-DAG to yield phosphatidic acid (PA). Our study adds an example of a promiscuous Cls enzyme able to synthesize a suite of products according to the available substrates.
细菌膜主要由磷脂酰乙醇胺（PE）、磷脂酰甘油（PG）和心磷脂（CL）组成。在典型的 PE 生物合成途径中，Psd 酶使磷脂酰丝氨酸（PS）脱羧。CL 的形成通常依赖于 CL 合成酶（Cls），以两个 PG 分子作为底物。只有少数细菌产生磷脂酰胆碱（PC），这是真核细胞膜的标志。这些细菌中的大多数利用磷脂 N-甲基转移酶将 PE 依次甲基化为 PC 和/或 PC 合酶（Pcs），以催化胆碱和 CDP-二酰基甘油（CDP-DAG）与 PC 的缩合。在这项研究中，我们表明能够与真核生物相互作用的假单胞菌属的膜含有 PE、PG、CL 和 PC。更具体地说，我们报告了植物病原体丁香假单胞菌 pv. tomato 中 PC 的形成和一个特征不明显的 CL 生物合成途径。它编码一种 Pcs 酶，负责依赖胆碱的 PC 生物合成。CL 的形成由一种混杂的磷脂酶 D（PLD）型酶（PSPTO_0095）催化，我们在体内和体外对其进行了表征。与典型的细菌 CL 生物合成酶一样，它使用 PE 和 PG 来生产 CL。该酶还能够将 PE 和甘油转化为 PG，然后将其与另一个 PE 分子结合以合成 CL。此外，该酶能够将乙醇胺或甲基化衍生物转化为相应的磷脂，如 PE，无论是在丁香假单胞菌还是大肠杆菌中。它还可以水解 CDP-DAG 生成磷脂酸（PA）。我们的研究增加了一个例子，即一种混杂的 Cls 酶能够根据可用的底物合成一整套产物。
