Extraction and preliminary characterization of microsomal (Mg<sup>2+</sup> + K<sup>+</sup>)-ATPase activity of grapevine roots

Authors

  • Z. Varanini
  • A. Maggioni

DOI:

https://doi.org/10.5073/vitis.1985.24.199-207

Keywords:

root, cell, enzyme, mineral, magnesium, potassium, additive, acidity, absorption

Abstract

The microsomal fraction extracted from grapevine roots obtained from woody cuttings possesses Mg2+-dependent, monovalent cation-stimulated ATPase activity. Addition of BSA, PVPP, choline-CI, ethanolamine, glycerol-1-P besides EDTA and DTT to the homogenizing medium as preservative compounds was required in order to achieve a successful isolation.
When microsomes were extracted according to HODGES and LEONARD (1974) by homogenizing root tissue in the presence of EDTA and DTT, the enzyme activity exhibited inhibition by Mg2+ only partially relieved by K+, and properties of acid phosphatase rather than ATPase.
Cation-stimulated ATPase of microsomes protected during homogenization was further characterized and it showed optimum activity at pH 7.0 in the presence of Mg2+ plus K+ . It was specific as a triphosphatase and Mg2+, rather than other divalent cations, was preferred as a cofactor. As monovalent stimulating cation, only NH4+ could substitute for K+ with equivalent efficiency. The kinetics of K+ stimulation showed a biphasic pattern.
Biochemical bases of ion uptake by grapevine seem to be similar to those clarified for annual plants.

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Published

2015-12-17

Issue

Vol. 24 No. 3 (1985): VITIS

Section

Article

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