Characterization of glycogen and amino acid pool of Entamoeba histolytica by 13C-NMR spectroscopy.

Trophozoite extracts of axenic Entamoeba histolytica were investigated by natural-abundance 13C-NMR spectroscopy. The extracts were found to contain a high level of glycogen (30 mM glucose equivalents), which had a compact structure as suggested by alpha (1-->6) branch points every 5-6 glucose residues. As other major metabolites, we identified putrescine (9.5 mM) and the following free amino acids: tyrosine and phenylalanine (1 mM), glycine, lysine and methionine (2 mM), isoleucine (5 mM), proline and valine (6-7 mM), leucine (11 mM) and glutamate (22 mM). Glutamate and proline may serve, together with putrescine, as intracellular osmolytes.