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Kinetics of Na+, K+-ATPase inhibition by a rat brain endogenous factor (II-E)
T Herbin1, C Peña, G Rodríguez de Lores Arnaiz
1Instituto de Biología Celular y Neurociencias Prof. Eduardo De Robertis, Facultad de Medicina, Universidad de Buenos Aires, Argentina.
Abstract:
Previous work from this laboratory led to the isolation by gel filtration and anionic exchange HPLC of a rat brain fraction named II-E, which highly inhibits synaptosomal membrane Na+, K+-ATPase activity. In this study we evaluated the kinetics of such inhibition and found that inhibitory potency was independent of Na+ (1.56-200 mM), K+ (1.25-40 mM), or ATP (1-8 mM) concentration. Hanes-Woolf plots indicated that II-E decreases Vmax but does not alter KM value, and suggested uncompetitive inhibition for Na+, K+ or ATP. However, II-E became a stimulator at 0.5 mM ATP concentration. It is postulated that this brain factor may modulate ionic transport at synapses, thus participating in central neurotransmission.