Biomedical Sciences Research Complex,Schools of Biology and Chemistry,University of St Andrews,Fife, KY16 9ST,UK.
Parasitology. 2019 Apr;146(5):604-616. doi: 10.1017/S0031182018001853. Epub 2018 Nov 5.
The kinetoplastid parasite Trypanosoma brucei causes African trypanosomiasis in both humans and animals. Infections place a significant health and economic burden on developing nations in sub-Saharan Africa, but few effective anti-parasitic treatments are currently available. Hence, there is an urgent need to identify new leads for drug development. The T. brucei neutral sphingomyelinase (TbnSMase) was previously established as essential to parasite survival, consequently being identified as a potential drug target. This enzyme may catalyse the single route to sphingolipid catabolism outside the T. brucei lysosome. To obtain new insight into parasite sphingolipid catabolism, the substrate specificity of TbnSMase was investigated using electrospray ionization tandem mass spectrometry (ESI-MS/MS). Recombinant TbnSMase was shown to degrade sphingomyelin, inositol-phosphoceramide and ethanolamine-phosphoceramide sphingolipid substrates, consistent with the sphingolipid complement of the parasites. TbnSMase also catabolized ceramide-1-phosphate, but was inactive towards sphingosine-1-phosphate. The broad-range specificity of this enzyme towards sphingolipid species is a unique feature of TbnSMase. Additionally, ESI-MS/MS analysis revealed previously uncharacterized activity towards lyso-phosphatidylcholine despite the enzyme's inability to degrade phosphatidylcholine. Collectively, these data underline the enzyme's importance in choline homoeostasis and the turnover of sphingolipids in T. brucei.
锥虫科寄生虫布氏锥虫会在人类和动物身上引起非洲锥虫病。这种感染给撒哈拉以南非洲的发展中国家带来了巨大的健康和经济负担,但目前可用的有效抗寄生虫治疗方法很少。因此,迫切需要确定新的药物开发线索。先前已确定布氏锥虫中性鞘磷脂酶(TbnSMase)对寄生虫的生存至关重要,因此被确定为潜在的药物靶点。这种酶可能催化了布氏锥虫溶酶体外唯一的神经鞘脂代谢途径。为了深入了解寄生虫神经鞘脂代谢,使用电喷雾电离串联质谱(ESI-MS/MS)研究了 TbnSMase 的底物特异性。结果表明,重组 TbnSMase 可降解鞘磷脂、肌醇磷酸神经酰胺和乙醇胺磷酸神经酰胺神经鞘脂底物,这与寄生虫的神经鞘脂成分一致。TbnSMase 还可以代谢神经酰胺-1-磷酸,但对鞘氨醇-1-磷酸没有活性。该酶对神经鞘脂种类的广泛特异性是 TbnSMase 的一个独特特征。此外,尽管该酶不能降解磷脂酰胆碱,但 ESI-MS/MS 分析显示其对溶血磷脂酰胆碱具有以前未表征的活性。这些数据共同强调了该酶在胆碱稳态和布氏锥虫神经鞘脂周转中的重要性。