Ref ID : 7278
Peter H.H. Weekers and Chris Van Der Drift; Nitrogen Metabolizing Enzyme Activities in the Free-Living Soil Amoebae Acanthamoeba castellanii, Acanthamoeba polyphaga and Hartmannella vermiformis. J.Eukaryot.Microbiol. 40(3):251-254, 1993
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Free-living soil amoebae consume a wide variety of food, including algae, yeast, small protozoa and especially bacteria, which they digest to fulfil their nutritional requirements. Amoebae play an active role in the nitrogen mineralization in soils due to their nitrogen metabolizing capacities. However, little is known about nitrogen metabolizing enzyme activities in these free-living soil amoebae. In this study a number of key enzymes involved in the nitrogen metabolism of the axenically cultivated free-living soil amoebae Acanthamoeba castellanii, Acanthamoeba polyphaga and two different strains of Hartmannella vermiformis were determined. The specific enzyme activities for exponential growth phase cells were calculated and it appeared that the species tested possessed urate oxidase, glutamine sythetase, NADH-dependent glutamate dehydrogenase, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase activity. Glutamate synthase activity could not be detected in any of these species. The levels of specific activities varied depending on the enzymes tested. For all species the highest activities were detected for the transaminase reactions yielding glutamate, and for glutamate dehydrogenase. A general conclusion is that the pathway of nitrogen assimilation in free-living soil amoebae is similar to the other observed for other eukaryotes. Differences in specific activities were detected between the species.