Electrophorus Adenosine Triphosphatase: Sodium-Activated Exchange after N -Ethyl Maleimide Treatment

Abstract

The microsomal fraction from the electric organ of the eel Electrophorus electricus catalyzes the hydrolysis of adenosine triphosphate in the presence of Mg⁺⁺, Na⁺, and K⁺. The same preparation catalyzes a Mg⁺⁺-dependent transphosphorylation between adenosine triphosphate and adenosine diphosphate. Both of these reactions are inhibited after treatment of the microsomes with N-ethyl maleimide. However, the addition of Na⁺ reactivates the transphosphorylation, and the rate becomes more rapid than that of the original. This new Na⁺-sensitive exchange reaction is believed to be a component of the hydrolytic reaction.