Regulation of Nicotinamide Adenine Dinucleotide Phosphate-specific Glutamate Dehydrogenase in Germinated Spores of Geotrichum candidum
- 1 May 1973
- journal article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 51 (5), 852-858
- https://doi.org/10.1104/pp.51.5.852
Abstract
Germinating spores of Geotrichum candidum produce only a nicotinamide adenine dinucleotide phosphate-linked glutamate dehydrogenase. Synthesis of glutamate dehydrogenase was repressed by the presence of ammonia, whereas urea, glutamate, or glutamine were ineffective. The enzyme was not subject to catabolite repression and was localized in the cell sap fraction. The glutamate dehydrogenase has been purified 93-fold and showed maximal activity at pH 8.2 in the forward and reverse directions. When measuring the initial reaction rate at pH 7.2, a variety of tricarboxylic acid cycle intermediates displayed additive and unidirectional activation of the reductive amination reaction and inhibition of the oxidative deamination reaction. The modulating effects were pH-dependent and diminished at alkaline pH values. Substrate inhibition exerted by alpha-ketoglutarate was strongest at neutral pH.Rate-concentration plot with respect to alpha-ketoglutarate at pH 7.2 was sigmoidal, and the enzyme was entirely inactive at substrate concentrations lower than 1 mm. In the presence of fumarate, the enzyme did not exhibit the cooperative interaction described above and was markedly activated at alpha-ketoglutarate concentrations lower than 1 mm. The tricarboxylic acid cycle intermediates released the enzyme from substrate inhibition by alpha-ketoglutarate. Double reciprocal rate-concentration plots displayed noncompetitive inhibition between succinate and NADP and a mixed noncompetitive and competitive inhibition between succinate and glutamate. The binding order of substrates in the reductive amination reaction was NADPH, alpha-ketoglutarate, and subsequently ammonia.Keywords
This publication has 21 references indexed in Scilit:
- Effect of Urea on Ammonium-dependent Synthesis of Carbamyl Phosphate during Spore Germination of Geotrichum candidumPlant Physiology, 1972
- Effect of the Microenvironment on the Mode of Action of Immobilized EnzymesPublished by Wiley ,1971
- The glutamate dehydrogenases of yeast: Extra-mitochondrial enzymesBiochimica et Biophysica Acta (BBA) - General Subjects, 1970
- Regulation of synthesis of glutamate dehydrogenase and glutamine synthetase in micro-organismsBiochemical Journal, 1969
- Size and charge isomer separation and estimation of molecular weights of proteins by disc gel electrophoresisArchives of Biochemistry and Biophysics, 1968
- On the nature of allosteric transitions: A plausible modelJournal of Molecular Biology, 1965
- The kinetics of enzyme-catalyzed reactions with two or more substrates or products☆III. Prediction of initial velocity and inhibition patterns by inspectionBiochimica et Biophysica Acta, 1963
- Di- and triphosphopyridine nucleotide linked glutamic dehydrogenases of Piricularia oryzae and their behaviors in glutamate mediaArchives of Biochemistry and Biophysics, 1962
- Concurrent regulation of glutamic acid dehydrogenases of NeurosporaArchives of Biochemistry and Biophysics, 1962
- Diphosphopyridine nucleotide and triphosphopyridine nucleotide linked glutamic dehydrogenases of fusariumArchives of Biochemistry and Biophysics, 1961