Transport ATPase—the different modes of inhibition of the enzyme by various mercury compounds

Abstract

The effects of a number of mercurials on the partial reactions of Na +, K +-ATPase were studied. Results of these studies allow a classification of the mercurials into two groups: selective modifiers of the enzyme and unspecific inhibitors. Thimerosal, ethylmercury and methylmercury were shown to selectively inhibit Na +, K +-ATPase while not affecting K +-NPPase, Na +-ATPase, ADP-ATP exchange reaction and phosphoenzyme formation. In contrast, p-chloromercuribenzoic acid, p-chloromercuriphenylsulfonic acid, mersalyl and mercuric chloride inhibited Na +, K +-ATPase as well as several partial reactions of the enzyme in a parallel manner. The selective modification of Na +, K +-ATPase by compounds such as ethylmercury and methylmercury makes these agents useful probes of the reaction mechanism of the enzyme. Whether this mode of inhibition of the enzyme is related to the mechanism of toxicity of short-chain alkylmercury compounds remains to be determined.