MG2-DEPENDENT ATPASES IN THE ELECTROCYTE OF ELECTROPHORUS-ELECTRICUS (L)()

The electrocyte, the elementary unit of the electric organ of Electrop horus, has distinct P-type ATPase activities which are Mg2+ 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 whe re transmembrane movements of Na+ and K+ ions are intense. The enzyme is situated both on the membranes of the non-innervated anterior and t he innervated posterior faces. Sucrose gradient centrifugation of thes e membranes indicated that the enzyme is present as two isoforms. Upon denervation of the elcctric organ there is a conspicuous decrease of the heavier isoform activity which is indicative of membrane structure alteration.