Sahonero-Canavesi Diana X, Sohlenkamp Christian, Sandoval-Calderón Mario, Lamsa Anne, Pogliano Kit, López-Lara Isabel M, Geiger Otto
Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Av. Universidad s/n, Apdo. Postal 565-A, Cuernavaca, Morelos, CP 62210, Mexico.
Division of Biological Sciences, University of California, San Diego, CA, 92093, USA.
Environ Microbiol. 2015 Sep;17(9):3391-406. doi: 10.1111/1462-2920.12814. Epub 2015 Mar 27.
Phospholipids are well known for their membrane-forming properties and thereby delimit any cell from the exterior world. In addition, membrane phospholipids can act as precursors for signals and other biomolecules during their turnover. Little is known about phospholipid signalling, turnover and remodelling in bacteria. Recently, we showed that a FadD-deficient mutant of Sinorhizobium meliloti, unable to convert free fatty acids to their coenzyme A derivatives, accumulates free fatty acids during the stationary phase of growth. Enzymatic activities responsible for the generation of these free fatty acids were unknown in rhizobia. Searching the genome of S. meliloti, we identified a potential lysophospholipase (SMc04041) and two predicted patatin-like phospholipases A (SMc00930, SMc01003). Although SMc00930 as well as SMc01003 contribute to the release of free fatty acids in S. meliloti, neither one can use phospholipids as substrates. Here we show that SMc01003 converts diacylglycerol to monoacylglycerol and a fatty acid, and that monoacylglycerol can be further degraded by SMc01003 to another fatty acid and glycerol. A SMc01003-deficient mutant of S. meliloti transiently accumulates diacylglycerol, suggesting that SMc01003 also acts as diacylglycerol lipase (DglA) in its native background. Expression of the DglA lipase in Escherichia coli causes lysis of cells in stationary phase of growth.
磷脂因其形成膜的特性而广为人知，从而将任何细胞与外部世界分隔开来。此外，膜磷脂在其周转过程中可作为信号和其他生物分子的前体。关于细菌中磷脂信号传导、周转和重塑的了解甚少。最近，我们发现苜蓿中华根瘤菌的一个FadD缺陷突变体无法将游离脂肪酸转化为其辅酶A衍生物，在生长稳定期积累游离脂肪酸。根瘤菌中负责产生这些游离脂肪酸的酶活性尚不清楚。通过搜索苜蓿中华根瘤菌的基因组，我们鉴定出一种潜在的溶血磷脂酶（SMc04041）和两种预测的类马铃薯Patatin磷脂酶A（SMc00930、SMc01003）。虽然SMc00930和SMc01003都有助于苜蓿中华根瘤菌中游离脂肪酸的释放，但它们都不能将磷脂用作底物。在这里我们表明，SMc01003将二酰基甘油转化为单酰基甘油和一种脂肪酸，并且单酰基甘油可被SMc01003进一步降解为另一种脂肪酸和甘油。苜蓿中华根瘤菌的一个SMc01003缺陷突变体短暂积累二酰基甘油，这表明SMc01003在其天然背景中也作为二酰基甘油脂肪酶（DglA）发挥作用。DglA脂肪酶在大肠杆菌中的表达导致生长稳定期的细胞裂解。
