Effect of growth conditions on nadph‐specific glutamate dehydrogenase activity of euglena gracilis
1985
FAYYAZ‐CHAUDHARY, M. | JAVED, QAMAR | MERRETT, MICHAEL J.
Cells of Euglena gracilis Klebs, strain z Pringsheim, had high NADPH‐glutamate dehydrogenase (GDH) activity when grown on glutamate but activity was repressed completely in cells grown on ammonium (NH₄⁺). Subcellular fractionation showed that NADPH‐GDH activity was located exclusively in the cytosol, while glutamine synthetase was present in the cytosol and chloroplasts. Despite high NADPH‐GDH activity NH₄⁺ assimilation was completely inhibited by methionine sulphoximine (MSO), an inhibitor of glutamine synthetase. With MSO present, cells produced NH₄⁺ and it was shown that greatest NH₄⁺ production occurred with cells containing high levels of NADPH‐GDH activity and plentiful carbon supply. It is concluded that NADPH‐GDH has a catabolic function in Euglena generating NH₄⁺ from glutamate under conditions of nitrogen limitation.
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