Phosphorylation and dephosphorylation reactions by erythrocyte plasma membrane enzymes

Human erythrocyte membranes contain a phosphoprotein phosphatase able to dephosphorylate membrane protein previously phosphorylated by the endogenous protein kinase. The level of dephosphorylation obtained after prolonged incubation is about one half of the phosphorylated residues. The characteristics of this enzyme are similar to those described for the cytoplasmic phosphoprotein phosphatase. In a membrane preparation the phosphorylation and dephosphorylation reactions can be repeated, at least twice, achieving similar levels of phosphate esterified or hydrolyzed. The coordination of these two enzyme systems might play a role in some of the functions attributed to the protein kinase system.