C-13 Labelling and electrospray mass spectrometry reveal a de novo route for inositol biosynthesis in Leishmania donovani parasite

In this paper we provide evidence for the presence of a de novo route for m yo-inositol biosynthesis in the protozoan parasite Leishmania donovani, by the application of C-13 labelling and electrospray ionisation mass spectrom etry (ESMS). For this myo-[1-C-13]inositol is prepared from D-[6-C-13]gluco se and biosynthetically incorporated in the parasite promastigote cell cult ure. Biosynthetic phosphatidylinositol (PI) and its hydrolysis products gly cero-PI and inositol are analysed by ESMS and the isotopomeric ratio determ ined. The incorporation experiments show substantial isotopic dilution, ind icating the presence of myo-inositol 1-phosphate synthase (MIP synthase) en zyme in the parasite; this is further confirmed by incorporation of D-[6-C- 13]glucose in the parasite phosphatidylinositol.