The Regulation of Nitrate Reductase, Nitrite Reductase, and Glutamate Dehydrogenase in Excised Pea Roots by Some Exogenous Amino Acids

1972 ◽  
Vol 14 (4) ◽  
pp. 308-311 ◽  
Author(s):  
J. Sahulka
Keyword(s):  
Amino Acids ◽  
Nitrate Reductase ◽  
Glutamate Dehydrogenase ◽  
Nitrite Reductase ◽  
Pea Roots

Glutamate Dehydrogenase from Pea Roots: Purification and Properties of the Enzyme

1971 ◽  
Vol 49 (1) ◽  
pp. 127-138 ◽  
Author(s):  
E. Pahlich ◽  
K. W. Joy
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Glutamate Dehydrogenase ◽  
Constant Ratio ◽  
Ph Optimum ◽  
Purification And Properties ◽  
Activity Ratios ◽  
Single Protein ◽  
Michaelis Constants ◽  
Pea Roots

Glutamate dehydrogenase (L-glutamate: NAD+ oxidoreductase (deaminating), EC 1.4.1.2) has been purified 1250-fold from pea roots. The preparation contains only a single protein, and the molecular weight was estimated to be 208 000 ± 10 000. The enzyme shows NADH (aminating) and NAD+ (deaminating) activities, but the ratio of these activities is not constant and can be changed experimentally. NADPH activity is also present and shows a relatively constant ratio to NAD+ activity. EDTA inhibits NADH activity in intermediate concentrations, but reactivates at higher concentrations. NAD+ (and NADPH) activity is only slightly changed by EDTA. The effects of dioxane and the coenzymes on the enzyme are also reported. Mechanisms which could explain the different activity ratios, in terms of two interconvertible enzyme forms, are discussed.The pH optimum for NADH and NAD+ activities is about pH 8.0. Michaelis constants were found to be: α-ketoglutarate, 3.3 × 10−3 M; ammonium (sulfate), 3.8 × 10−2 M; glutamate, 7.3 × 10−3 M; NADH, 8.6 × 10−4 M; NAD+, 6.5 × 10−4 M. The enzyme is highly specific for the substrates glutamate and α-ketoglutarate, showing no alanine or aspartate dehydrogenase activity, and no deamination with a range of amino acids.

Nitrate reductase, nitrite reductase and glutamate dehydrogenase levels in roots and leaves of maize seedlings

1976 ◽  
Vol 18 (4) ◽  
pp. 283-289 ◽  
Author(s):  
Tatiana Pšenáková ◽  
Otília Gašparíková ◽  
Anna Nižňanská
Keyword(s):  
Nitrate Reductase ◽  
Glutamate Dehydrogenase ◽  
Nitrite Reductase ◽  
Maize Seedlings

scholarly journals The regulation of activity of the enzymes involved in the assimilation of nitrate by higher plants

1966 ◽  
Vol 100 (3) ◽  
pp. 577-588 ◽  
Author(s):  
J Ingle ◽  
K W Joy ◽  
R H Hageman
Keyword(s):  
Nitrate Reductase ◽  
Glutamate Dehydrogenase ◽  
Nitrite Reductase ◽  
Actinomycin D ◽  
Higher Plants ◽  
Specific Inhibitor ◽  
Nitrate Assimilation ◽  
End Products ◽  
Regulation Of Activity

1. Possible mechanisms regulating the activities of three enzymes involved in nitrate assimilation, nitrate reductase, nitrite reductase and glutamate dehydrogenase, were studied in radish cotyledons. 2. Nitrate-reductase and nitrite-reductase activities are low in nitrogen-deficient cotyledons, and are induced by their substrates. 3. Glutamate dehydrogenase is present regardless of the nitrogen status, and the enzyme can be increased only slightly by long-term growth on ammonia. 4. Although nitrate is the best inducer of nitrate reductase, lower levels of induction are also obtained with nitrite and ammonia. The experiments did not distinguish between direct or indirect induction by these two molecules. 5. Nitrite reductase is induced by nitrite and only indirectly by nitrate. 6. The induction of both nitrate reductase and nitrite reductase is prevented by the inhibitors actinomycin D, puromycin and cycloheximide, indicating a requirement for the synthesis of RNA and protein. 7. The decay of nitrate reductase, determined after inhibition of protein synthesis, is slower than the synthesis of the enzyme. Nitrite reductase is much more stable than nitrate reductase. 8. The synthesis of nitrate reductase is not repressed by ammonia, but is repressed by growth on a nitrite medium. 9. There is no inhibition of nitrate reductase, nitrite reductase or glutamate dehydrogenase by the normal end products of assimilation, but cyanate is a fairly specific inhibitor of nitrate reductase.

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