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 Mg2+-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 Mg2+-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 Mg2+-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.
LOCALIZATION OF Na+, K+-ATPASE AND OTHER ENZYMES IN TELEOST PSEUDOBRANCH : I. Biochemical Characterization of Subcellular Fractions
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Leslie A. Dendy, Russell L. Deter, Charles W. Philpott; LOCALIZATION OF Na+, K+-ATPASE AND OTHER ENZYMES IN TELEOST PSEUDOBRANCH : I. Biochemical Characterization of Subcellular Fractions . J Cell Biol 1 June 1973; 57 (3): 675–688. doi: https://doi.org/10.1083/jcb.57.3.675
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