Effect of adenine nucleotides on the reaction catalyzed by pyruvate,orthophosphate dikinase in maize |
| |
| Affiliation: | 1. Servicio de Hematología-Oncología, Hospital de Pediatría “Prof. Dr. Juan P. Garrahan”, Combate de los Pozos 1881, (C1245AAM) Buenos Aires, Argentina;2. Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina;3. IQUIBICEN/UBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina;4. Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina;5. IQUIBICEN/UBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina;6. U.O.C. Ematologia, U.O.S. FisiopatologiadelleAnemie, Fondazione IRCCS Ca Granada, OspedaleMaggiore Policlínico, Milan, Italy;1. Department of Neonatology, Wilhelmina Children''s Hospital, University Medical Center Utrecht, Utrecht, The Netherlands;2. Department of Genetics, University Medical Center Utrecht, Utrecht, The Netherlands;3. Department of Pediatric Neurology, Brain Center Rudolf Magnus, Wilhelmina Children''s Hospital, University Medical Center Utrecht, Utrecht, The Netherlands;4. Department of Medical Genetics, University Medical Center Groningen, Groningen, The Netherlands;5. Metabolic Unit, Department of Clinical Chemistry, VU University Medical Center/Neuroscience Campus, Amsterdam, The Netherlands;6. Department of Neonatology, Isala Clinics, Zwolle, The Netherlands;7. Pediatric Neurology Discipline, Department of Clinical Neurosciences, “Carol Davila” University of Medicine, Bucharest, Romania;8. Pediatric Neurology Clinic, Alexandru Obregia Hospital, Bucharest, Romania;1. Department of Neurology, The Second Hospital of Hebei Medical University, Shijiazhuang, Hebei 050000, China;2. Neurological Laboratory of Hebei Province, Shijiazhuang, Hebei 050000, China;3. Institute of Cardiocerebrovascular Disease, Shijiazhuang, Hebei 050000, China;1. Department of Biology, Carleton University, Ottawa, Ontario, Canada;2. Center for Environmental Epigenetics and Development, Biological Sciences, University of Toronto, Toronto, Ontario, Canada |
| |
| Abstract: | The effect of adenine nucleotides in pyruvate, orthophosphate dikinase (EC 2.7.9.1, ATP, pyruvate, orthophosphate phosphotransferase)_was studied with the enzyme furified from maize, and with the enzyme obtained from mesophyll chloroplast extracts during assay in the direction of pyruvate conversion to phosphoenolpyruvate. (1) In studies with the purified enzyme, the relationship of initial velocity to ATP concentrations follows Michaelis-Menten kinetics, and the Km value for ATP was 22.8 μM (± 5.1 μM, n = 5). (2) AMP was a competitive inhibitor with respect to ATP, and its Ki value was 35.8 μM (± μM, n = 4). There was no inhibition of catalysis by ADP up to a concentration of 460 μM. (3) The theoretical response of the enzyme to change in the adenylate energy charge was calculated from the kinetic constants for ATP and AMP. The experimentally obtained values were similar to the theoretical response when varying energy charge was generated by addition of appropriate amounts of ATP, ADP and AMP in assays with the purified enzyme. The response of the enzyme to energy charge at different pH values (pH 7.0, 7.5, and 8.0) was similar, although the activity of the enzyme at pH 7.0 was about 40% of that at pH 8.0. (4) When mesophyll chloroplast extracts of maize, which contain high levels of adenylate kinase, were used as the source of the enzyme and the adenylate energy charge was generated by addition of different concentrations of ATP and AMP, the influence on catalysis was similar to that with the purified enzyme. (5) The data show that the effect of varying energy chage on the activity of the dikinase is not typical of a U-type enzyme, in contrast to phosphoglycerate kinase (EC 2.7.2.3, ATP: 3-phospho-D-glycerate 1-phosphotransferase), which is more strongly regulated. (6) Evidence is presented for competition between the dikinase and phosphoglycerate kinase for ATP in mesophyll chloroplast extracts of maize. (7) When the effect of adenylate energy charge on the state of activation and the direct effect on catalysis of the dikanase are combined, the total capacity for catalysis is very dependent on the energy charge. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
