A p-nitrophenylphosphatase activity associated with the human erythrocyte membrane

A p-nitrophenylphosphatase activity has been identified as a component of the human erythrocyte membrane. This activity is distinct from that associated with the cell's Na(+)+K(+)-dependent ATPase, Ca(2+)-dependent ATPase, or spectrin phosphatase. The activity described here is stimulated by Mn2+ but not by Ca2+ with or without calmodulin. A potential erythrocyte membrane substrate for this activity is a 95 kDa phosphoprotein that can be shown to undergo Mn(2+)-stimulated but not Mg(2+)-stimulated dephosphorylation.