The possibility that Ca2+-ATPase from the plasma membrane-rich fraction of bovine parotid gland is ecto-Ca2+-dependent nucleoside triphosphatase |
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| Institution: | 1. Graduate School of Pharmaceutical Sciences and School of Pharmacy, Duquesne University, Pittsburgh, PA, USA;2. Department of Anesthesiology, School of Medicine, University of Colorado Anschutz Medical Campus, Aurora, CO, USA;3. College of William & Mary, Williamsburg, VA, USA;4. Heart, Lung, Blood Vascular Institute, University of Pittsburgh Medical School, PA, USA;5. Department of Pharmacology & Chemical Biology, Pittsburgh Heart Lung Blood Vascular Institute, University of Pittsburgh Medical School, PA, USA;6. Department of Biomedical Informatics, University of Pittsburgh Medical School, PA, USA |
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| Abstract: | - 1.1. Parotid plasma membrane nonpump low-affinity Ca2+-ATPase, which possesses high-affinity (Ca2+ + Mg2+ )-ATPase activity, was characterized.
- 2.2. Purified Ca2+-ATPase hydrolyzed the nucleoside triphosphates, GTP, ITP, CTP, UTP, TTP (67–93% of ATP) and nucleoside diphosphates, ADP. GDP, IDP, CDP, TDP (12–40% of ATP) but not AMP and p-NPP.
- 3.3. The maximum activities of Ca2+- and (Ca2+ +Mg2+ )-ATPases were obtained in the presence of 1 mM and 0.13 μ M Ca2+, respectively.
- 4.4. The Km values for Ca2+ in Ca2+- and (Ca2++ Mg2+ )-ATPases were 0.2 mM and 22 nM. respectively.
- 5.5. The activities of both Ca2+- and (Ca2+ + Mg2+ )-ATPases were found in the right-side-out-vesicles obtained from the plasma membrane-rich fraction.
- 6.6. These features suggest that Ca2+-ATPase is an ecto-Ca2+-dependent nucleoside triphosphatase.
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