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Adenosine Triphosphatases Bound to Plasmalemma, Mitochondria, and Microsomes or Present in the Cytoplasmic Phase from Potato Tubers
Author(s) -
JOLLIOT ALAIN,
DEMANDRE CHANTAL,
MAZLIAK PAUL
Publication year - 1976
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1976.tb04005.x
Subject(s) - oligomycin , divalent , atpase , atp hydrolysis , microsome , chemistry , biochemistry , cytoplasm , enzyme , substrate (aquarium) , mitochondrion , membrane , biophysics , biology , ecology , organic chemistry
Between pH 4–10, basal ATPase activity, measured in the absence of mineral ions, was 10 to 100 times higher in the final cytoplasmic supernatant from potato tuber homogenates than in the membraneous fractions (purified plasmalemma, purified mitochondria and microsomes). The soluble ATPase was slightly inhibited, whereas the membrane‐bound ATPases were all stimulated by Mg 2+ ions. A further stimulation by Na + or K + ions was only observed in purified plasmalemma or mitochondria, at alkaline pH (7.5–9.5). At a fixed (Na + + K + ) concentrations (80 m M ), this last stimulation was much greater in purified mitochondria (350%) than in plasmalemma (33%); it also increased with (Na + + K + ) concentrations up to 200 m M in mitochondria whereas, in plasmalemma, it was roughly constant for monovalent ion concentrations between 20 and 200 m M . General properties of the plasma membrane‐bound ATPase have been determined, i.e. substrate specificity, activity variations with quantity of substrate, temperature, pH, etc . Divalent cations stimulated strongly the ATPase in the following order: Mn 2+ > Mg 2+ > Ca 2+ . The maximum ATP hydrolysis velocity for that part of ATPase activity which is strictly dependent on Mg 2+ ions was 3.85 μmol × mg −1 protein × h −1 . This plasma membrane ATPase was not sensitive to ouabaïn or to oligomycin.