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Published on: January 18, 2014
EFFECT OF GROWTH CONDITIONS ON NADPH-SPECIFIC GLUTAMATE DEHYDROGENASE ACTIVITY OF EUGLENA GRACILIS
M Fayyaz-Chaudhary1, Qamar Javed1, Michael J Merrett1
1Department of Botany and Microbiology, University College, Singleton Park, Swansea SA2 8PP, UK.
Abstract:
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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