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The High-Affinity (Ca2+ —Mg2+ )ATPase of Rat Liver Plasma Membrane Hydrolyzes Extracellular ATP

  • Sue-Hwa Lin
Part of the GWUMC Department of Biochemistry Annual Spring Symposia book series (GWUN)

Abstract

The intracellular free Ca2+ concentration is very low (in the region of 0.1µM) in contrast to extracellular [Ca2+ ], which is usually in the millimolar range. An energy-dependent Ca2+ transporter in the plasma membrane is therefore important in maintaining the concentration gradient. Studies on the biochemical properties of a Ca2+ pump were first carried out with sarcoplasmic reticulum membrane that is enriched with a Ca2+ pump (for review, see Tadaet al., 1978). These studies established several properties of the sarcoplasmic reticulum Ca2+ pump: (1) The Ca2+ pump utilizes both Ca2+ -and Mg2+ -ATP as substrates. (2) It exhibits a high affinity for Ca2+ (in the submicromolar range). (3) It has a Ca2+ -stimulated ATPase activity. When the enzyme is incorporated into phospholipid vesicles, a coupled Ca2+ -stimulated ATP hydrolysis and Ca2+ transport can be demonstrated. (4) The mechanism of Ca2+ -stimulated ATP hydrolysis involves an enzyme phosphate intermediate. As a result of such a property, both the Ca2+ -stimulated ATP hydrolysis and Ca2+ transport can be inhibited by vanadate, a transition state analog of phosphate.

Keywords

ATPase Activity Sarcoplasmic Reticulum Phospholipid Vesicle Liver Plasma Membrane Lactate Dehydrogenase Activity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • Sue-Hwa Lin
    • 1
  1. 1.Department of Biochemistry and Molecular BiologyHarvard UniversityCambridgeUSA

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