Mg2+-dependent ATPases in the electrolyte of Electrophorus electricus (L.)

The electrocyte, the elementary unit of the electric organ of Electrophorus, has distinct P-type ATPase activities which are Mg 2+ dependent and named according to the cations they translocate. The Na + /K + -ATPase (E.C.3.6.1.3) has been studied more extensively in the electrocyte where transmembrane movements of Na + and K + ions are intense. The enzyme is situated both on the membranes of the non-innervated anterior and the innervated posterior faces. Sucrose gradient centrifugation of these membranes indicated that the enzyme is present as two isoforms. Upon denervation of the electric organ there is a conspicuous decrease of the heavier isoform activity which is indicative of membrane structure alteration