Further characterization of the plasma membrane- and intracellular membrane-associated platelet Ca2+ transport systems

J. Enouf, R. Bredoux, N. Bourdeau, B. Sarkadi, S. Levy-Toledano

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30 Citations (Scopus)

Abstract

Biochemical characterization of the Ca2+-ATPases isolated from human platelet intracellular and plasma membranes is reported. A comparative study of the previously partly described plasma membrane Ca2+-ATPase [Enouf, Bredoux, Bourdeau and Levy-Toledano (1987) J. Biol. Chem. 261, 9293-9297] and the intracellular membrane Ca2+-ATPase obtained simultaneously shows differences in the following parameters: (1) different kinetics of the two enzymes; (2) similar apparent affinity towards Ca2+ (10-7 M), though the intracellular membrane enzyme was inhibited at Ca2+ concentrations above 10-6 M; (3) different pH dependence with an activity maximum at pH 7 for the intracellular membrane Ca2+-ATPase and no detectable pH maximum for the plasma membrane Ca2+-ATPase; (4) a 10-fold difference in the ATP requirement of the two Ca2+-ATPases; (5) different patterns of inhibition by vanadate. Finally, the possible regulation of the Ca2+-ATPases was examined by studying the effect of chlorpromazine on the two Ca2+-ATPase activities, with only the plasma membrane enzyme being inhibited. It is concluded that the two platelet Ca2+ transport systems show biochemical differences in spite of the previously shown similarity in the molecular masses of their Ca2+-ATPases, thus conferring a definite specificity to the platelet system.

Original languageEnglish
Pages (from-to)547-552
Number of pages6
JournalBiochemical Journal
Volume263
Issue number2
DOIs
Publication statusPublished - 1989

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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