Stimulation of low Km cyclic AMP phosphodiesterase by sulphydryl modification

Low concentrations of the organic mercurials, p-chloromercuribenzoate or p-chloromercuriphenylsulphonate activate the particulate low Km phosphodiesterase from adipose tissue and liver. Higher concentrations are inhibitory. Enzyme which has been activated by treatment of adipocytes with insulin, is not activated by the organic mercurials although inhibition by higher concentrations is seen. Enzyme from non-insulin treated adipocytes is activated and solubilised by mild trypsin treatment. Enzyme activated by either insulin treatment, or by p-chloromercuribenzoate is not further activated by trypsin, but it is solubilised.