Divalent cation-activated ecto-nucleoside triphosphatase activity of nervous system cells in tissue culture.

Abstract

Abstract— Intact neuroblastoma and glial cells in monolayer culture hydrolysed ATP added to their medium. Evidence is presented that ATP is cleaved outside of the permeability barrier of the plasma membrane and the product is liberated in the extracellular medium, i.e. the enzyme is an ecto‐enzyme. Divalent cations such as Mg2+, Ca2+, Mn2+ and Co2+ activate the enzyme. In neuroblastoma cells, Ca2+ is the preferential cation for activation; Mg2+ in glial cells. Substrate specificity was very low when different nucleoside‐5′‐triphosphates were examined. Competition studies have revealed that all of the nucleoside triphosphates are hydrolysed by the same enzyme: divalent cation‐activated ecto‐nucleoside‐5′‐triphosphate phosphohydrolase.Developmental pattern of the enzyme in several lines was established. The role of enzyme in the transport of divalent cations across the plasma membrane and/or in the physical properties of the membrane is suggested.