Properties of pyruvate kinase from soybean nodule cytosol.
Jay B. Peterson,Harold J. Evans +1 more
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It is concluded that control of cytosol pyruvate kinase may be closely related to reactions involved in the assimilation of NH(4) (+), and apparent K(a) and K(m) (PEP) were influenced by PEP and monovalent cation concentrations, respectively.Abstract:
The properties of pyruvate kinase from soybean (Glycine max L.) nodule cytosol were examined to determine what influence the N2 fixation process might have on this supposed key control enzyme. A crude enzyme preparation was prepared by chromatography of cytosol extract on a diethylaminoethyl-cellulose column. ATP and citrate at 5 mm concentrations inhibited pyruvate kinase 27 and 34%, respectively. Enzyme activation was hyperbolic with respect to both K+ and NH4+ concentrations. In the presence of physiological concentrations of K+ and high phosphoenolpyruvate (PEP) concentrations, NH4+ inhibited enzyme activity. Comparisons of kinetic parameters (Vmax and apparent Ka) for NH4+ and K+ with inhibition curves indicated that inhibition was very likely a result of competition of the ions for activation site(s) on the pyruvate kinase. In addition, apparent Ka (monovalent cation) and Km (PEP) were influenced by PEP and monovalent cation concentrations, respectively. This effect may reflect a fundamental difference between plant and animal pyruvate kinases. It is concluded that control of cytosol pyruvate kinase may be closely related to reactions involved in the assimilation of NH4+.read more
Citations
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Journal ArticleDOI
Carbon and nitrogen metabolism in legume root nodules
TL;DR: The pathways of carbon flow in nitrogen metabolism, particularly in relation to the synthesis of ureides and the regulation of carbon metabolism, remain key areas for future research in symbiotic nitrogen fixation.
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Transport and Metabolism of Carbon and Nitrogen in Legume Nodules
TL;DR: It is on these unique qualities of nodules that this chapter focuses, in the hope that there are some useful lessons to be learned both by the general plant physiologist and by those struggling to understand the chemical interactions of the plant and bacterium.
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References
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Journal ArticleDOI
The pathway of nitrogen assimilation in plants
Benjamin J. Miflin,Peter J. Lea +1 more
TL;DR: There is other evidence to support the contention that the assimilation of ammonia into amino acids occurs via glutamine synthetase and glutamate synthase, and that it is unlikely that glutamate dehydrogenase plays a major role in nitrogen assimilation in bacteria or higher plants except in circumstances of ammonia excess.
Journal ArticleDOI
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J.F. Kachmar,P.D. Boyer +1 more
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Journal ArticleDOI
The Carbon Balance of a Legume and the Functional Economy of its Root Nodules
F. R. Minchin,J. S. Pate +1 more
TL;DR: The respiratory efficiency of a nodulated root in terms of nitrogen fixation is found to be very similar to that of an uninoculated root assimilating nitrate, and the nodules require in growth, respiration, and export 4-1 mg C for each mg N which they fix.
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