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  • Title: Activation of (Na+, K+)-ATPase by nanomolar concentrations of GM1 ganglioside.
    Author: Leon A, Facci L, Toffano G, Sonnino S, Tettamanti G.
    Journal: J Neurochem; 1981 Aug; 37(2):350-7. PubMed ID: 6267200.
    Abstract:
    GM1 ganglioside binding to the crude mitochondrial fraction of rat brain and its effect on (Na+, K+)-ATPase were studied, the following results being obtained: (a) the binding process followed a biphasic kinetics with a break at 50 nM-GM1; GM1 at concentrations below the break was stably associated, while over the break it was loosely associated; (b) stably bound GM1 activated (Na+, K+)-ATPase up to a maximum of 43%; (c) the activation was dependent upon the amount of bound GM1 and was highest at the critical concentration of 20 pmol bound GM1 X mg protein-1; (d) loosely bound GM1 suppressed the activating effect on (Na+, K+)-ATPase elicited by firmly bound GM1; (e) GM1-activated (Na+, K+)-ATPase had the same pH optimum and apparent Km (for ATP) as normal (Na+, K+)-ATPase but a greater apparent Vmax; (f) under identical binding conditions (2 h, 37 degrees C, with 40 nM substance) all tested gangliosides (GM1, GD1a, GD1b, GT1b) activated (Na+, K+)-ATPase (from 26-43%); NeuNAc, sodium dodecylsulphate, sulphatide and cerebroside had only a very slight effect. It is suggested that the ganglioside activation of (Na+-K+)-ATPase is a specific phenomenon not related to the amphiphilic and ionic properties of gangliosides, but due to modifications of the membrane lipid environment surrounding the enzyme.
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