PARTIAL-PURIFICATION AND PROPERTIES OF THE INHIBITORS OF NA,K-ATPASE AND OUABAIN-BINDING IN BOVINE CENTRAL NERVOUS-SYSTEM

Endogenous inhibitors of Na,K-ATPase and ouabain-binding were partially purified from bovine CNS, and some of their properties were studied. They were eluted as low-MW fractions by gel filtration. They could be adsorbed by both Amberlite IR 120 and Amberlite IRA 400 at acidic and basic pH, respectively, indicating that they could act as both anions and cations at different pH. These inhibitors of ouabain-binding appeared to affect specific binding of ouabin, and Scatchard plot analysis showed the inhibition was competitive, suggesting they could bind to the same site as ouabain, presumably to Na,K-ATPase itself. The inhibitory activities were heat stable, but charring inactivated them completely.