Metabolites of the Free‐Living Amoeba Phreatamoeba balamuthi Analyzed by ¹³C‐ and ³¹P‐NMR Spectroscopy: Occurrence of Phosphoinositol Diphosphates

Phreatamoeba balamuthi is a free‐living heterotrophic amoeba that lacks mitochondria. Metabolites of axenically‐grown cells were characterized by natural‐abundance 13 C‐NMR and 31 P‐NMR spectroscopy on acellular perchloric acid extracts. The amoebae were found to contain glycogen and trehalose as storage carbohydrates, together with putrescine and several amino acids, most prominently proline; we propose that proline and trehalose may serve in osmoregulation. Glycerophosphocholine and glycerophosphoethanolamine were present with their phosphomonoester derivatives, phosphocholine and phosphoethanolamine. Along with inorganic phosphate, inorganic pyrophosphate, nucleoside diphosphates, nucleoside triphosphates and NAD, P. balamuthi amoebae also contained unusual phosphoinositol diphosphates in large quantities (0.5 μmol/g wet cells).