Location of two isoenzymes of NADH-dependent glutamate synthase in root nodules of Phaseolus vulgaris L. |
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Authors: | Feng-Ling Chen Julie V Cullimore |
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Institution: | (1) Department of Biological Sciences, University of Warwick, CV4 7AL Coventry, UK |
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Abstract: | The two isoenzymes of NADH-dependent glutamate synthase (NADH-GOGAT; EC 1.4.1.14), previously identified in root nodules of Phaseolus vulgaris L., have both been shown to be located in root-nodule plastids. The nodule specific NADH-GOGAT II accounts for the majority of the activity in root nodules, and is present almost exclusively in the central tissue of the nodule. However about 20% of NADH-GOGAT I activity is present in the nodule cortex, at about the same specific activity as this isoenzyme is found in the central tissue. Glutamine synthetase (GS; EC 6.3.1.2) occurs predominantly as the polypeptide in the central tissue, whereas in the cortex, the enzyme is represented mainly by the polypeptide. Over 90% of both GS and NADH-GOGAT activities are located in the central tissue of the nodule and GS activity exceeds NADH-GOGAT activity by about twofold in this region. Using the above information, a model for the subcellular location and stoichiometry of nitrogen metabolism in the central tissue of P. vulgaris root nodules is presented.Abbreviations Fd-GOGAT
ferredoxin-dependent glutamate synthase
- GOGAT
glutamate synthase
- GS
glutamine synthetase
- NADH-GOGAT
NADH-dependent glutamate synthase
- IEX-HPLC
ion-exchange high-performance liquid chromatography |
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Keywords: | Glutamate synthase Glutamine synthetase Nitrogen fixation Phaseolus (glutamate synthase) Plastid (glutamate synthase) Root nodule |
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