Variable ATPase composition of human tumor plasma membranes |
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Authors: | A F Knowles N O Kaplan |
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Institution: | 1. Department of Chemistry University of California at San Diego La Jolla, Ca. 92093 USA;2. the Cancer Center University of California at San Diego La Jolla, Ca. 92093 USA |
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Abstract: | Purified plasma membranes from several transplantable human tumors exhibit very high Mg2+-dependent ATPase activities. Three types of Mg2+-dependent ATPases can be demonstrated: (1) an ouabain sensitive Na+, K+-ATPase, which is a minor component of the tumor plasma membrane ATPase, (2) a Mg2+-activated ATPase, which is a non-specific nucleoside triphosphatase, and (3) an ATPase activity stimulated by Na+ (or K+) alone. In three human melanomas, only the first two activities are found. In an astrocytoma and an oat cell carcinoma, all three activities are found. In the same two tumors, the plasma membrane Mg2+-ATPase is also stimulated by Con A. The relationship of these ATPases are discussed. |
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