Some Kinetic Features of Na,K-ATPase and Sensitivity to Noradrenaline.
Cell Biochem Biophys 2021;
80:23-29. [PMID:
34436718 DOI:
10.1007/s12013-021-01032-6]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 08/04/2021] [Indexed: 10/20/2022]
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.
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