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EFFECT OF GROWTH CONDITIONS ON NADPH‐SPECIFIC GLUTAMATE DEHYDROGENASE ACTIVITY OF EUGLENA GRACILIS
Author(s) -
FAYYAZCHAUDHARY M.,
JAVED QAMAR,
MERRETT MICHAEL J.
Publication year - 1985
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1985.tb02843.x
Subject(s) - euglena gracilis , glutamine synthetase , glutamate dehydrogenase , biochemistry , cytosol , biology , ammonium , cell fractionation , glutamate receptor , glutamine , enzyme , chloroplast , chemistry , amino acid , receptor , organic chemistry , gene
S ummary 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 (NH 4 + ). 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 NH 4 + assimilation was completely inhibited by methionine sulphoximine (MSO), an inhibitor of glutamine synthetase. With MSO present, cells produced NH 4 + and it was shown that greatest NH 4 + 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 NH 4 + from glutamate under conditions of nitrogen limitation.