A thraustochytrid-specific lipase/phospholipase with unique positional specificity contributes to microbial competition and fatty acid acquisition from the environment
A thraustochytrid-specific lipase/phospholipase with unique positional specificity contributes to microbial competition and fatty acid acquisition from the environment
复制标题
DOI：
10.1038/s41598-019-52854-7
复制
发表时间：
2019-11-08
影响因子：
4.6
通讯作者：
Ito, Makoto
中科院分区：
文献类型：
--
作者：
Ishibashi, Yohei;Aoki, Keisuke;Ito, Makoto
破囊壶菌是异养海洋原生生物，被认为是海洋生态系统中重要的分解者;然而，它们如何从环境中消化和吸收脂质营养物质在很大程度上是未知的。利用破囊壶菌基因组草图数据库进行的基因组聚类分析显示，具有脂肪酶_3结构域的新蛋白质普遍存在于破囊壶菌中，包括橙壶菌（Aurantiochytriumlimacinum）。在异源表达和基于His标签的纯化后，蛋白ID：145138被鉴定为能够水解三酰甘油（TG）和磷脂酰胆碱（PC）的脂肪酶/磷脂酶。145138基因在A.利马辛减少细胞外脂质的降解。145138产生的脂肪酸可重复用于PC和TG的生物合成，145138允许A. limacinum在含有TG作为唯一碳源的培养基中存活。145138水解TG的所有酰基-酯键;然而，该酶对磷脂显示出严格的位置特异性，产生2-酰基溶血磷脂。与1-酰基溶血磷脂相比，2-酰基溶血磷脂具有更强的抗菌活性。这些结果表明，145138是一种双功能酶，有助于从环境中获取脂质营养素，以及产生抗菌溶血磷脂，有利于与海洋环境中的细菌竞争脂质营养素。
Thraustochytrids are heterotrophic marine protists that are considered as important decomposers in the marine ecosystem; however, how they digest and uptake lipid nutrients from the environment is largely unknown. Genomic clustering analysis using thraustochytrid draft genome databases revealed that novel proteins with a Lipase_3 domain are commonly present in thraustochytrids, including Aurantiochytrium limacinum. After heterologous expression and His tag-based purification, protein ID: 145138 was identified as lipase/phospholipase capable of hydrolyzing triacylglycerol (TG) and phosphatidylcholine (PC). 145138 was secreted into the medium, and deletion of the 145138 gene in A. limacinum reduced the degradation of extracellular lipids. Fatty acids generated by 145138 were reused for the biosynthesis of PC and TG, and 145138 allowed A. limacinum to survive in the medium containing TG as a sole carbon source. 145138 hydrolyzed all the acyl-ester linkages of TG; however, the enzyme showed strict positional specificity toward phospholipids, generating 2-acyl lysophospholipids. The 2-acyl lysophospholipids showed stronger antimicrobial activity compared with 1-acyl lysophospholipids. These results suggested that 145138 is a bifunctional enzyme that contributes to the acquisition of lipid nutrients from the environment, as well as to generate antimicrobial lysophospholipids that are beneficial for competition with bacteria over lipid nutrients in the marine environment.