title: Characterization of gill (Na+ + K+)-ATPase in the sea bass (Dicentrarchus labrax L.).
abstract: Bass gill microsomal preparations contain both a Na+, K+ and Mg2+-dependent ATPase, which is completely inhibited by 10(-3)M ouabain and 10(-2)M Ca2+, and also a ouabain insensitive ATP-ase activity in the presence of both Mg2+ and Na+. Under the optimal conditions of pH 6.5, 100 mM Na+, 20 mM K+, 5 mM ATP and 5 mM Mg2+, (Na+ + K+)-ATPase activity at 30 degrees C is 15.6 mumole Pi hr/mg protein. Bass gill (Na+ + K+)-ATPase is similar to other (Na+ + K+)-ATPases with respect to the sensitivity to ionic strength, Ca2+ and ouabain and to both Na+/K+ and Mg2+/ATP optimal ratios, while pH optimum is lower than poikilotherm data. The enzyme requires Na+, whereas K+ can be replaced efficiently by NH+4 and poorly by Li+. Both Km and Vm values decrease in the series NH+4 greater than K+ greater than Li+. The break of Arrhenius plot at 17.7 degrees C is close to the adaptation temperature. Activation energies are scarcely different from each other and both lower than those generally reported. The Km for Na+ poorly decreases as the assay temperature lowers. The comparison with literature data aims at distinguishing between distinctive and common features of bass gill (Na+ + K+)-ATPase.
authors.forename: G
authors.initials: G
authors.lastname: Trigari
authors.forename: A R
authors.initials: AR
authors.lastname: Borgatti
authors.forename: A
authors.initials: A
authors.lastname: Pagliarani
authors.forename: V
authors.initials: V
authors.lastname: Ventrella
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D005399:Fishes / Q000378:metabolism*; D005880:Gills / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D008861:Microsomes / Q000201:enzymology; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013696:Temperature
chemical_list: D010042:Ouabain; D000255:Adenosine Triphosphate; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D011188:Potassium; D002118:Calcium