Isolation of stimulatory modulator from rat brain and its specific effect on guanosine 3′:5′-monophosphate-dependent protein kinase from cerebellum and other tissues

Abstract

The stimulatory and the inhibitory activities of protein kinase modulator originally present in the crude modulator preparation obtained from rat brain was separated by Sephadex G-100 gel filteration. The isolated stimulatory modulator, as the crude modulator, augmented the activity of guanosine 3′:5′-monophosphate (cGMP)-dependent protein kinase from both the mammalian tissues (cerebellum, heart and lung) and the lobster tail muscle. The purified cGMP-dependent protein kinase was not activated by cGMP unless the stimulatory modulator, or the crude modulator, was added. The isolated inhibitory modulator, as the crude modulator, on the other hand, depressed the activity of adenosine 3′:5′-monophosphate (cAMP)-dependent protein kinase. It neither inhibited nor stimulated the activity of cGMP-dependent protein kinase.