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. 1975 Jan;55(1):83–86. doi: 10.1104/pp.55.1.83

Plasma Membrane Adenosine Triphosphatase of Oat Roots

Activation and Inhibition by Mg2+ and ATP 1

Nelson E Balke a, Thomas K Hodges a
PMCID: PMC541555  PMID: 16659034

Abstract

ATPase activity of plasma membrane vesicles isolated from oat (Avena sativa L. cv. Goodfield) roots was examined in the presence of various concentrations of MgCl2 and ATP. A Mg2+: ATP ratio of about 1 was required for maximal activity regardless of the concentrations used; the optimum concentration for both Mg2+ and ATP was 9 mm. Based on the ATPase activity at different concentrations of complexed Mg·ATP and free ATP, it is concluded that Mg·ATP is the true substrate of this enzyme.

Under certain experimental conditions, high concentrations of MgCl2 and ATP inhibited the plasma membrane ATPase. On the basis of the relative amounts of free and complexed ATP and Mg2+, it was found that the different moieties caused different amounts of inhibition. Free ATP inhibited the ATPase at concentrations in excess of 2 mm. Mg·ATP concentrations above 11 mm inhibited the enzyme. Free Mg2+ caused only a slight inhibition of the ATPase.

The Km for Mg·ATP was found to vary from 0.64 to 1.24 mm depending on the experimental conditions. This variation is thought to be due to variable amounts of Mg·ATP, which serves as an inhibitor as well as the substrate, and free ATP, which also inhibits the enzyme.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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