The (Na+, K+)ATPase exhibits enzymic activity in the absence of the glycoprotein subunit

Membrane-bound (Na+, K+)ATPase from avian nasal salt glands was exposed to limited papain digestion. Such treatment results in the selective removal of the beta-subunit rendering the alpha-subunit still membrane-bound and expressing full enzymic activity. With further exposure to papain the alpha-chain becomes fragmented into two major polypeptide components. The fragmented membrane-bound catalytic chain is extremely sensitive to detergent treatment and cannot be solubilized in an active state.