While recent advances in metabolomic measurement technologies have been dramatic, extracting biological insight from complex metabolite profiles remains a challenge. We present an analytical strategy that uses data obtained from high resolution liquid chromatography–mass spectrometry and a bioinformatics toolset for detecting actively changing metabolic pathways upon external perturbation. We begin with untargeted metabolite profiling to nominate altered metabolites and identify pathway candidates, followed by validation of those pathways with transcriptomics. Using the model organisms Rhodospirillum rubrum and Bacillus subtilis, our results reveal metabolic pathways that are interconnected with methionine salvage. The rubrum-type methionine salvage pathway is interconnected with the active methyl cycle in which re-methylation, a key reaction for recycling methionine from homocysteine, is unexpectedly suppressed; instead, homocysteine is catabolized by the trans-sulfuration pathway. Notably, the non-mevalonate pathway is repressed, whereas the rubrum-type methionine salvage pathway contributes to isoprenoid biosynthesis upon 5′-methylthioadenosine feeding. In this process, glutathione functions as a coenzyme in vivo when 1-methylthio-d-xylulose 5-phosphate (MTXu 5-P) methylsulfurylase catalyzes dethiomethylation of MTXu 5-P. These results clearly show that our analytical approach enables unexpected metabolic pathways to be uncovered.
虽然近年来代谢组学测量技术取得了巨大进步,但从复杂的代谢物图谱中提取
生物信息仍是一项挑战。我们提出了一种分析策略,利用从高分辨率
液相色谱-质谱联用仪获得的数据和
生物信息学工具集,检测在外部扰动下发生积极变化的代谢途径。我们首先通过非靶向代谢物分析来确定发生变化的代谢物并确定候选通路,然后通过转录组学对这些通路进行验证。利用模式
生物红柱菌(Rhodospirillum rubrum)和
枯草芽孢杆菌(Bacillus subtilis),我们的研究结果揭示了与蛋
氨酸挽救相互关联的代谢途径。红球菌型蛋
氨酸挽救途径与活跃的甲基循环相互关联,其中从同半胱
氨酸回收蛋
氨酸的关键反应--再甲基化--意外地被抑制;相反,同半胱
氨酸通过反式
硫化途径被分解。值得注意的是,非甲羟
戊酸途径受到抑制,而红宝石型甲
硫氨酸挽救途径在摄入 5′-甲
硫基
腺苷后有助于
异戊二烯的
生物合成。在这一过程中,当 1-甲
硫基-d-
木酮糖-5-
磷酸(
MTXu 5-P)甲基
硫化酶催化
MTXu 5-P 的脱
硫化作用时,
谷胱甘肽在体内作为辅酶发挥作用。这些结果清楚地表明,我们的分析方法能够发现意想不到的代谢途径。