Biochemical characterization of the initial steps of the Kennedy pathway in Trypanosoma brucei: the ethanolamine and choline kinases

Federica Gibellini, William N. Hunter, Terry K. Smith

    Research output: Contribution to journalArticlepeer-review

    27 Citations (Scopus)
    222 Downloads (Pure)


    Ethanolamine and choline are major components of the trypanosome membrane phospholipids, in the form of GPEtn (glycero-phosphoethanolamine) and GPCho (glycerophosphocholine). Ethanolamine is also found as an integral component of the GPI (glycosylpliosphatidylinositol) anchor that is required for membrane attachment of cell-surface proteins, most notably the variant-surface glycoproteins. The de novo synthesis of GPEtn and GPCho starts with the generation of phosphoethanolamine and phosphocholine by ethanolamine and choline kinases via the Kennedy pathway. Database mining revealed two putative C/EKs (choline/ethanolamine kinases) in the Trypanosoma brucei genome, which were cloned, overexpressed, purified and characterized. TbEK 1 (T brucei ethanolamine kinase 1) was shown to be catalytically active as an ethanolamine-specific kinase, i.e. it had no choline kinase activity. The K values for ethanolamine and ATP were found to be 18.4 +/- 0.9 and 219 29 mu M respectively. TbC/EK2 (T brucei choline/ethanolamine kinase 2), on the other hand, was found to be able to phosphorylate both ethanolamine and choline, even though choline was the preferred substrate, with a K-m 80 times lower than that of ethanolamine. The K. values for choline, ethanolamine and ATP were 31.4 +/- 2.6 mu M, 2.56 +/- 0.31 mu M and 20.6 +/- 1.96 mu M respectively. Further substrate specificity analysis revealed that both TbEK1 and TbC/EK2 were able to tolerate various modifications at the amino group, with the exception of a quaternary amine for TbEK1 (choline) and a primary amine for TbC/EK2 (ethanolamine). Both enzymes recognized analogues with substituents oil C-2, but substitutions oil C-1 and elongations of the carbon chain were not well tolerated.
    © 2008 The Author(s)
    The author(s) has paid for this article to be freely available under the terms of the Creative Commons Attribution Non-Commercial Licence (
    which permits unrestricted non-commerical use, distribution and reproduction in any medium, provided the original work is properly cited.

    Original languageEnglish
    Pages (from-to)135-144
    Number of pages10
    JournalBiochemical Journal
    Publication statusPublished - 2008


    • choline kinase
    • ethanolamine kinase
    • Kennedy pathway
    • Trypanosoma brucei
    • DONOR


    Dive into the research topics of 'Biochemical characterization of the initial steps of the Kennedy pathway in Trypanosoma brucei: the ethanolamine and choline kinases'. Together they form a unique fingerprint.

    Cite this