França, Juliana L.Pinto, Marcelo R.Lucena, Malson N.Garçon, Daniela P.Valenti, Wagner Cotroni [UNESP]McNamara, John C.Leone, Francisco A.2014-05-272014-05-272013-07-01Journal of Membrane Biology, v. 246, n. 7, p. 529-543, 2013.0022-26311432-1424http://hdl.handle.net/11449/75736The stimulation by Mg2+, Na+, K+, NH 4 +, and ATP of (Na+, K+)-ATPase activity in a gill microsomal fraction from the freshwater prawn Macrobrachium rosenbergii was examined. Immunofluorescence labeling revealed that the (Na +, K+)-ATPase α-subunit is distributed predominantly within the intralamellar septum, while Western blotting revealed a single α-subunit isoform of about 108 kDa M r. Under saturating Mg2+, Na+, and K+ concentrations, the enzyme hydrolyzed ATP, obeying cooperative kinetics with V M = 115.0 ± 2.3 U mg-1, K 0.5 = 0.10 ± 0.01 mmol L-1. Stimulation by Na+ (V M = 110.0 ± 3.3 U mg-1, K 0.5 = 1.30 ± 0.03 mmol L -1), Mg2+ (V M = 115.0 ± 4.6 U mg -1, K 0.5 = 0.96 ± 0.03 mmol L-1), NH4 + (V M = 141.0 ± 5.6 U mg -1, K 0.5 = 1.90 ± 0.04 mmol L-1), and K+ (V M = 120.0 ± 2.4 U mg-1, K M = 2.74 ± 0.08 mmol L-1) followed single saturation curves and, except for K+, exhibited site-site interaction kinetics. Ouabain inhibited ATPase activity by around 73 % with K I = 12.4 ± 1.3 mol L-1. Complementary inhibition studies suggest the presence of F0F1-, Na+-, or K +-ATPases, but not V(H+)- or Ca2+-ATPases, in the gill microsomal preparation. K+ and NH4 + synergistically stimulated enzyme activity (≈25 %), suggesting that these ions bind to different sites on the molecule. We propose a mechanism for the stimulation by both NH4 +, and K+ of the gill enzyme. © 2013 Springer Science+Business Media New York.529-543eng(Na+, K+)-ATPaseAmmonium/potassium stimulationATPGiant freshwater prawnGill microsomeMacrobrachium rosenbergiiadenosine triphosphatase (calcium)adenosine triphosphatase (potassium sodium)adenosine triphosphatase (potassium)adenosine triphosphateammoniamagnesium ionouabainpotassium ionproton transporting adenosine triphosphataseproton transporting adenosine triphosphate synthasesodium ionalpha chaincellular distributioncontrolled studyenzyme activityenzyme inhibitionenzyme kineticsgillhemolymphhydrolysisimmunofluorescenceimmunolocalizationmicrosomenonhumanWestern blottingStrophanthus gratusArtigo10.1007/s00232-013-9565-4WOS:000321133600004Acesso restrito2-s2.0-848813181020588804414769477