Dissociation of rat liver high molecular weight phosphorylase phosphatase by salt

The chromatography of rat liver crude extract (10 000 x g supernatant) on a Biogel A-0.5 m column resulted in two peaks of phosphorylase phosphatase activity. The first peak, eluted in void volume, is of microsomal origin whereas the second peak, a cytoplasmic origin, was eluted with an apparent molecular weight of 260 000. In the presence of NaCl, the cytosolic enzyme was dissociated into intermediary (Mr = 135 000 and 68 000) and low molecular weight (Mr = 35 000) forms with an apparent activation of the enzyme activity. Similar dissociation was observed in the presence of KCl and (NH4)2SO4. A partially purified high molecular weight phosphorylase phosphatase was also dissociated into the low molecular weight form by 0.2 M NaCl. However, a protein phosphatase showing activity towards 32P-labelled histone was not dissociated by 0.2 M NaCl or 0.1 M (NH4)2SO4.