title: Localization of Na + , K + -ATPase and other enzymes in teleost pseudobranch. I. Biochemical characterization of subcellular fractions.
abstract: In an effort to determine the subcellular localization of sodium- and potassium-activated adenosine triphosphatase (Na(+), K(+)-ATPase) in the pseudobranch of the pinfish Lagodon rhomboides, this tissue was fractionated by differential centrifugation and the activities of several marker enzymes in the fractions were measured. Cytochrome c oxidase was found primarily in the mitochondrial-light mitochondrial (M+L) fraction. Phosphoglucomutase appeared almost exclusively in the soluble (S) fraction. Monoamine oxidase was concentrated in the nuclear (N) fraction, with a significant amount also in the microsomal (P) fraction but little in M+L or S. Na(+), K(+)-ATPase and ouabain insensitive Mg(2+)-ATPase were distributed in N, M+L, and P, the former having its highest specific activity in P and the latter in M+L. Rate sedimentation analysis of the M+L fraction indicated that cytochrome c oxidase and Mg(2+)-ATPase were associated with a rapidly sedimenting particle population (presumably mitochondria), while Na(+), K(+)-ATPase was found primarily in a slowly sedimenting component. At least 75% of the Na(+), K(+)-ATPase in M+L appeared to be associated with structures containing no Mg(2+)-ATPase. Kinetic properties of the two ATPases were studied in the P fraction and were typical of these enzymes in other tissues. Na(+), K(+)-ATPase activity was highly dependent on the ratio of Na(+) and K(+) concentrations but independent of absolute concentrations over at least a fourfold range.
mesh_terms: D000251:Adenosine Triphosphatases / Q000302:isolation & purification*; D000818:Animals; D002458:Cell Fractionation; D002462:Cell Membrane / Q000201:enzymology; D002467:Cell Nucleus / Q000201:enzymology; D002499:Centrifugation, Density Gradient; D003576:Electron Transport Complex IV / Q000302:isolation & purification; D005399:Fishes / Q000201:enzymology*; D005880:Gills / Q000166:cytology / Q000201:enzymology*; D008861:Microsomes / Q000201:enzymology; D008928:Mitochondria / Q000201:enzymology; D008995:Monoamine Oxidase / Q000302:isolation & purification; D010733:Phosphoglucomutase / Q000302:isolation & purification; D011188:Potassium; D012964:Sodium; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D012964:Sodium; D008995:Monoamine Oxidase; D003576:Electron Transport Complex IV; D000251:Adenosine Triphosphatases; D010733:Phosphoglucomutase; D011188:Potassium