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. 2022 Mar;80(1):23-29.
doi: 10.1007/s12013-021-01032-6. Epub 2021 Aug 26.

Some Kinetic Features of Na,K-ATPase and Sensitivity to Noradrenaline

Gvantsa Chkadua  1 , Eka Nozadze  2 , Leila Tsakadze  2 , Lia Shioshvili  2 , Marine Leladze  2 , Nana Arutinova  2 , Sopio Dzneladze  2 , Maia Javakhishvili  2 , Sopio Kupradze  2
Affiliations

Some Kinetic Features of Na,K-ATPase and Sensitivity to Noradrenaline

Gvantsa Chkadua et al. Cell Biochem Biophys. 2022 Mar.

Abstract

A comparative kinetic analysis of albino rat brain synaptic and kidney plasma membrane fraction Na,K-ATPase was performed to comprehend the different levels of sensitivity of these fractions to the neurotransmitter noradrenaline. Noradrenaline (NA) inhibits the rat brain synaptic membrane Na,K-ATPase, changes the stoichiometry of Na+ and K+ and shifts the enzyme system from an MgATP to an Mg2+ dependent cycle. While the kidney plasma membrane fraction Na,K-ATPase is not sensitive to noradrenaline. To investigate the mechanism underlying this difference, we studied enzyme velocity dependence on the concentration of Mg2+. The 1/V = f(Mg2+) function has shown different kinetic features for the synaptic and kidney plasma membrane Na,K-ATPase. With the addition of ethylene glycol tetraacetic acid (EGTA) to the reaction medium the geometric form of 1/V = f(Mg2+) function is affected differently. We thereafter measured the essential activator number for Na+ and K+ with, in excess Mg2+. The results of these experiments reveal that, contrary to the synaptic membrane Na,K-ATPase, the kidney plasma membrane fraction Na,K-ATPase does not possess an Mg2+ dependent cycle and noradrenaline exhibits different modulatory effects on the enzyme system.

Keywords: Enzyme kinetics; Multi-sited enzyme systems; Na,K-ATPase; Neurotransmitter.

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