<綜説>細胞膜における能動輸送とNa^+, K^+-ATPase
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概要
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Active transports of sugars, amino acids and cations across the cell membrane and Na^+, K^+-ATPase which acts as the molecular mechanism of sodium-potassium pump are characterized. DOPA (2,4-dihydroxyphenylalanine) is an amino acid and a precursor of catecholamine in the brain and is uptaken into brain tissue from the circulation system through the blood brain barrier and cell membrane. The uptake of L-DOPA was found to be accumulated against the concentration gradient in brain slices by energy dependent process. Sodium pump which consists of Na^+, K^+-ATPase supplied driving force on the active transport of this amino acid. Na^+, K^+-ATPase activity was dependent on the coexistence of Mg^<2+>, Na^+, and K^+ and inhibited by ouabain which is a cardiac glycoside. The active transports of Na^+ and K^+ are also dependent on the presence of both Na^+ and K^+ and inhibited by ouabain. Then, membrane Na^+, K^+-ATPase was regarded as a main component of Na^+, K^+ pump. Molecular size of K^+-dependent phosphatase which reflects a dephosphorylating step, was half that of Na^+, K^+-ATPase. Nucleotide binding and cation bindings to Na^+, K^+-ATPase were demontsrated. Stoichiometry of phosphorylation, ADP binding, ouabain binding and Na^+ binding on Na^+, K^+-ATPase was 1 : 1 : 1 : 3. This ratio agrees with the stoichiometry expected if 3 moles of sodium are transported per mol of the ATP hydrolyzed. A physiological regulation of Na^+, K^+-ATPase activity by vanadate and NADH was also described.
- 近畿大学の論文
- 1981-09-25