The bacterial domain produces numerous types of sphingolipids with various physiological functions. In the human microbiome, commensal and pathogenic bacteria use these lipids to modulate the host inflammatory system. Despite their growing importance, their biosynthetic pathway remains undefined since several key eukaryotic ceramide synthesis enzymes have no bacterial homolog. Here we used genomic and biochemical approaches to identify six proteins comprising the complete pathway for bacterial ceramide synthesis. Bioinformatic analyses revealed the widespread potential for bacterial ceramide synthesis leading to our discovery of a Gram-positive species that produces ceramides. Biochemical evidence demonstrated that the bacterial pathway operates in a different order from that in eukaryotes. Furthermore, phylogenetic analyses support the hypothesis that the bacterial and eukaryotic ceramide pathways evolved independently. Elucidation of the bacterial ceramide biosynthetic pathway reveals that it likely evolved independently from the eukaryotic pathway, as bacteria lack homologs for many of the eukaryotic enzymes and the reactions occur in a different order.
细菌域产生多种类型的神经酰胺,它们具有多种生理功能。在人类微
生物组中,共生和致病细菌利用这些脂质来调节宿主的炎症系统。尽管它们的重要性日益增加,但它们的
生物合成途径仍未明确,因为几种关键的真核
生物神经酰胺合成酶在细菌中没有同源物。我们通过
基因组和生化方法识别了六种蛋白质,完整构成了细菌神经酰胺合成的途径。
生物信息学分析揭示了细菌神经酰胺合成的广泛潜力,从而使我们发现了一种能产生神经酰胺的革兰氏阳性菌。生化证据表明,细菌途径的运作顺序与真核
生物的不同。此外,系统发育分析支持细菌和真核
生物神经酰胺途径独立进化的假说。对细菌神经酰胺
生物合成途径的阐明表明,它可能独立于真核
生物途径进化,因为细菌缺乏许多真核
生物酶的同源物,并且反应顺序不同。