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The Effect of Magnesium and Calcium Ions on Adenosine Triphosphatases from Wheat and Oat Roots at Different pH
Author(s) -
KYLIN A.,
KÄHR M.
Publication year - 1973
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.1399-3054.1973.tb08588.x
Subject(s) - avena , chemistry , atpase , salt (chemistry) , magnesium , adenosine , calcium , stimulation , adenosine triphosphatase , microsome , biochemistry , enzyme , botany , biology , organic chemistry , neuroscience
Microsomal fractions from wheat ( Triticum vulgare ) and oat ( Avena sativa ) roots were used to study Mg 2+ and Ca 2+ activated adenosine triphosphatases, their dependence of pH, and how Mg 2+ and Ca 2+ compete or add in stimulation and inhibition. Wheat gives a high proportion of Ca 2+ stimulated ATPase. Less effect is obtained with Mg 2+ . The characteristics of oar ATPase are the reverse. The ATPase from the wheat roots depends on the mineral nutrition. A kinetïc analysis shows one site, where Mg 2+ and Ca 2+ at low concentrations (or complexes between the di‐valents and ATP) cooperate in the activation of the ATPase. The action of this site is more dearly expressed at pH 6.0 than at 6.8, and more clearly in the preparations from low salt roots than in those from high salt conditions. In another site, which is particularly evident in preparations from high salt roots tested at pH 6.8, high concentrations of Mg 2+ inhibit the ATPase; this inhibition is competitively relieved by Ca 2+ . The specific activity of the ATPase from high salt roots of wheat is higher than that from low salt roots, although the amount of protein of the fraction studied remains the same, when calculated per g fresh weight of the roots.