Further characterization of the membrane-bound (Ca2+ + Mg2+)-ATPase from porcine erythrocytes |
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| Authors: | C O Bewaji E A Bababunmi |
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| Institution: | 1. Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, VA, USA;2. Public Health Sciences, University of Virginia, Charlottesville, VA, USA;3. Department of Pediatrics, University of Virginia, Charlottesville, VA, USA;4. Medical Research Council Unit, Banjul, The Gambia;5. Global Disease Detection Division, Kenya Office of the US Centers for Disease Control and Prevention, Nairobi, Kenya;6. Center for Global Health Research, Kenya Medical Research Institute, Nairobi, Kenya;7. International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR, B), Dhaka, Bangladesh;8. Department of Paediatrics and Child Health, Aga Khan University, Karachi, Pakistan;9. Center for Vaccine Development and Institute of Global Health, University of Maryland School of Medicine, Baltimore, MD, USA;10. Department of Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA;11. Department of Medicine, University of Maryland School of Medicine, Baltimore, MD, USA;12. Centre pour le Développement des Vaccins, Bamako, Mali;13. Centro de Investigação em Saúde da Manhiça, Maputo, Mozambique;14. National Institute of Cholera and Enteric Diseases, Kolkata, India;15. Barcelona Centre for International Health Research (CRESIB, Hospital Clinic-Universitat de Barcelona), Barcelona, Spain;1. School of Pharmaceutical Science and Technology, Tianjin University, Tianjin 300072, China;2. Department of Pharmacy, Logistics College of Chinese People’s Armed Police Forces, Tianjin Key Laboratory of Cardiovascular Remodeling and Target Organ Injury, Tianjin 300162, China;3. The State Key Laboratories of Pharmacodynamics and Pharmacokinetics, Tianjin, China |
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| Abstract: | 1. The kinetic and physicochemical properties of the calcium-pumping protein, (Ca2+ + Mg2+)-ATPase (ATP phosphohydrolase, EC 3.6.1.3) were studied in ghost membranes isolated from porcine erythrocytes. 2. The membrane-bound enzyme in situ has a specific activity of 3.12 +/- 0.08 micron/mg protein/hr and a Vmax of 3.47 +/- 0.21 mumol/mg protein/hr in the absence of calmodulin. 3. Its activity was stimulated by calmodulin about 5-fold. The enzyme is also highly sensitive to inhibition by vanadate (Ki = 1.6 +/- 0.2 microM). 4. Calmodulin also affects the pH- and Ca2+-sensitivity of the enzyme. The optimum pH, in the presence of calmodulin, is 7.5 and the optimum temperature is 38 degrees C with an activation energy of 11.9 kcal/mol. |
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