Enhanced activation of human erythrocyte Ca2+-ATPase by calmodulin after storage or brief exposure to disulfite.
Ca2+-ATPase of human erythrocyte membranes which are prepared from freshly drawn human blood can be activated by the calmodulin present in the hemolysate to 1.5-times the basal level. However, when the membranes are prepared from blood stored for 5-14 days the activation by calmodulin reaches 2.5-times the basal level. An enhanced reactivity to calmodulin of similar magnitude was produced by brief exposure of fresh erythrocytes to 25 mM Na2S2O5 prior to isolation of the membranes. Reincubation of the activated cells in a disulfite-free medium restored the membrane-bound Ca2+-ATPase to a state of normal reactivity to calmodulin. It is hypothesized that these results are related to the level of cytoplasmic Ca2+ which is partly controlled by complex formation with 2,3-diphosphoglycerate, the concentration of which is diminished when its specific phosphatase is activated by Na2S2O5.
D001800:Blood Specimen Collection; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D000252:Calcium-Transporting ATPases / Q000097:blood*; D002147:Calmodulin / Q000494:pharmacology*; D004789:Enzyme Activation; D004910:Erythrocyte Membrane / Q000201:enzymology*; D004912:Erythrocytes / Q000201:enzymology*; D005615:Freezing; D006801:Humans; D007700:Kinetics; D013447:Sulfites / Q000494:pharmacology*
D002135:Calcium-Binding Proteins; D002147:Calmodulin; D013447:Sulfites; C005200:sodium metabisulfite; D000252:Calcium-Transporting ATPases