Effect of gangliosides on Na,K-ATPase activity and conformation of microsomal membranes

The effect of gangliosides on activity of Na,K-ATPase and K-dependent nitrophenyl-phosphatase was studied. Gangliosides in low concentrations were shown to activate Na,K-ATPase, but to inhibit it in high concentrations. In all concentrations used the gangliosides had only an inhibitory action on K-dependent nitrophenyl-phosphatase. Inhibition of the enzyme by gangliosides was reversible and competitive relative to K+. Calculation of Hill's coefficient showed that gangliosides, whether their action was activating or inhibitory, behaved as allosteric effectors. To elucidate the mechanism of action of gangliosides on the enzyme their effect on microsomal membranes was studied by the fluorescent probe method. Gangliosides were found to produce marked conformational changes in microsomal membranes of the brain.