Calcium-stimulated ATPase of dog submandibular gland |
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Authors: | E L Watson K T Izutsu I A Siegel |
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Institution: | Departments of Oral Biology and Pharmacology and Centre for Research in Oral Biology, University of Washington, Seattle, Washington 98195, U.S.A. |
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Abstract: | A Ca2?-stimulated ATPase present in a microsomal fraction prepared from canine submandibular glands was investigated. The Ca2+ concentration for half maximal activation of the enzyme was about 0.3 mM. Addition of Mg2+ to incubation media containing Ca2+ decreased the ATPase activity. The presence of neither Na+ nor K+ is required for Ca2+-activation of the enzyme. Also, Ca2+ will not substitute for Mg2+ in the Mg2+-dependent (Na+ + K+)-ATPase reaction. The Ca2+-activation was not appreciably affected by ouabain (10?4M), but was inhibited by about 50 per cent by 5 × 10?3M ethacrynic acid. These studies provide a possible enzymatic basis for the calcium uptake by salivary gland microsomes that has been reported by other workers. |
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