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  • Title: Kinetic characterization of the gill (Na+, K+)-ATPase in a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).
    Author: Fabri LM, Lucena MN, Garçon DP, Moraes CM, McNamara JC, Leone FA.
    Journal: Comp Biochem Physiol B Biochem Mol Biol; 2019 Jan; 227():64-74. PubMed ID: 30267892.
    Abstract:
    We provide a kinetic characterization of (Na+, K+)-ATPase activity in a posterior gill microsomal fraction from a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum. Sucrose density gradient centrifugation reveals two distinct membrane fractions showing considerable (Na+, K+)ATP-ase activity, but also containing other microsomal ATPases. Only a single immune-reactive (Na+, K+)-ATPase with Mr of ≈110 kDa is present that hydrolyzes ATP with VM = 130.3 ± 4.8 nmol Pi min-1 mg protein-1 and K0.5 = 0.065 ± 0.00162 mmol L-1, exhibiting site-site interactions. Stimulation by Na+ (VM = 127.5 ± 5.3 nmol Pi min-1 mg protein-1, K0.5 = 5.3 ± 0.42 mmol L-1), Mg2+ (VM = 130.6 ± 6.8 nmol Pi min-1 mg protein-1, K0.5 = 0.33 ± 0.042 mmol L-1), K+ (VM = 126.7 ± 7.7 nmol Pi min-1 mg protein-1, K0.5 = 0.65 ± 0.0079 mmol L-1) and NH4+ (VM = 134.5 ± 8.6 nmol Pi min-1 mg protein-1, K0.5 = 1.28 ± 0.44 mmol L-1) also obeys cooperative kinetics. Ouabain (KI = 0.18 ± 0.058 mmol L-1) inhibits total ATPase activity by ≈70%. This study reveals considerable differences in the kinetic characteristics of the gill (Na+, K+)-ATPase in a hololimnetic population that appear to result from the adaptation of diadromous Macrobrachium amazonicum populations to different limnic habitats.
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