Glutamine synthetase regulation by energy charge in sunflower roots |
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| Authors: | Weissman G S |
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| Affiliation: | Department of Biology, Rutgers University, Camden College of Arts and Sciences, Camden, New Jersey 08102. |
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| Abstract: | Energy charge [(ATP) + ½ (ADP)]/[(ATP) + (ADP) + (AMP)] and glutamine synthetase activity (transferase reaction) of roots increase in a near congruent manner when decotyledonized sunflower plants (Helianthus annuus L. var. Mammoth Russian) are grown in nitrate for 9 days. Replacement of nitrate with ammonium for the final 2 days leads to a higher energy charge and increased enzyme activity. Similar correlations occur when nitrate plants are placed on a zero nitrogen regimen and when they are subjected to continuous darkness. A rank order correlation of 0.72 is obtained for all data. Control concepts such as adenylylation-deadenylylation and ammonium inhibition of enzyme synthesis are not supported by the data. Energy charge-enzyme activity plots support the view that glutamine synthetase of sunflower roots is subject to control by end products of glutamine metabolism. Alanine appears to exert a modulating effect on the regulation of glutamine synthetase by energy charge. |
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