The inactivation and dissociation of Escherichia coli succinyl-CoA synthetase by sulfhydryl reagents

1. 1. In immunodiffusion experiments antiserum to carboxymethylated succinyl-CoA synthetase (succinate:CoA ligase (ADP), EC 6.2.1.5) reacted strongly with subunits prepared by treatment of the enzyme with merthiolate (ethylmercurithiosalicylate), but not with native enzyme. 2. 2. Various parameters of inactivation and reactivation of the enzyme in the presence of merthiolate were studied. These included the effects of pH, temperature, protein concentration and merthiolate concentration. 3. 3. Titration of succinyl-CoA synthetase with p-chloromercuri[¹⁴C]benzoate led to the binding of 4 moles of mercurial per mole of enzyme. The enzyme was dissociated by either merthiolate or p-chloromercuribenzoate into what appeared to be two different kinds of subunits.