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neo-inositol polyphosphates in the amoeba Entamoeba histolytica
J B Martin1, T Laussmann, T Bakker-Grunwald
1Département de Biologie Moléculaire et Structurale/Laboratoire de Résonance Magnétique en Biologie Métabolique, CEA-Grenoble, 38054 Grenoble, France.
Abstract:
We have reexamined the structure of inositol phosphates present in trophozoites of the parasitic amoeba Entamoeba histolytica and show here that, rather than being myo-inositol derivatives (Martin, J.-B., Bakker-Grunwald, T., and Klein, G. (1993) Eur. J. Biochem. 214, 711-718), these compounds belong to a new class of inositol phosphates in which the cyclitol isomer is neo-inositol. The structures of neo-inositol hexakisphosphate, 2-diphospho-neo-inositol pentakisphosphate, and 2, 5-bisdiphospho-neo-inositol tetrakisphosphate, which are present in E. histolytica at concentrations of 0.08-0.36 mM, were solved by two-dimensional (31)P-(1)H NMR spectroscopy. No evidence for the co-existence of their myo-inositol counterparts has been found. These neo-inositol compounds were not substrates of 6-diphospho-inositol pentakisphosphate 5-kinase, an enzyme purified from Dictyostelium discoideum that phosphorylates 6-diphospho-myo-inositol pentakisphosphate and more slowly also myo-inositol hexakisphosphate, specifically on position 5. Because preliminary data indicate that large amounts of the same neo-inositol phosphate and diphosphate esters are also present in another primitive amoeba, Phreatamoeba balamuthi, the occurrence of high concentrations of neo-inositol polyphosphates may be much more general than previously thought.
Insights
Parasitic amoeba Entamoeba histolytica contains novel neo-inositol phosphates, not myo-inositol derivatives. These compounds, identified via NMR, suggest neo-inositol polyphosphates may be common in primitive amoebas.
Area of Science:
- Biochemistry
- Cell Biology
- Parasitology
Background:
- Inositol phosphates are crucial signaling molecules in eukaryotes.
- Previous studies identified myo-inositol derivatives in Entamoeba histolytica.
- The precise structure and occurrence of inositol phosphates in this parasite require further investigation.
Purpose of the Study:
- To reexamine and elucidate the structure of inositol phosphates in Entamoeba histolytica trophozoites.
- To determine if these compounds are myo-inositol derivatives or a novel class.
- To investigate the potential prevalence of these compounds in other primitive amoebas.
Main Methods:
- Two-dimensional (31)P-(1)H NMR spectroscopy was employed to solve the structures.
- Biochemical assays were used to test substrate specificity with a known kinase.
- Comparative analysis with related amoeba species was performed.
Main Results:
- Inositol phosphates in Entamoeba histolytica are neo-inositol derivatives, not myo-inositol.
- Structures of neo-inositol hexakisphosphate, 2-diphospho-neo-inositol pentakisphosphate, and 2,5-bisdiphospho-neo-inositol tetrakisphosphate were determined.
- These neo-inositol compounds are not substrates for 6-diphospho-inositol pentakisphosphate 5-kinase.
- Preliminary data suggest similar compounds exist in Phreatamoeba balamuthi.
Conclusions:
- Entamoeba histolytica possesses a novel class of inositol phosphates based on neo-inositol.
- The findings challenge previous assumptions about inositol phosphate structures in this organism.
- The widespread occurrence of neo-inositol polyphosphates in primitive amoebas is a significant possibility.