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Stimulation by inositol trisphosphate and tetrakisphosphate of a protein phosphatase
J Zwiller1, E M Ogasawara, S S Nakamoto
1Cancer Research Center of Hawaii, University of Hawaii, Honolulu 96813.
Abstract:
Several inositol trisphosphate isomers and inositol tetrakisphosphate activate a rat brain phosphoprotein phosphatase, using phosphohistone as well as phosphorylase kinase as substrate. Inositol mono- and bisphosphate have no effect. The protein phosphatase may correspond to type-1 since it is associated with the particulate fraction and is inhibited by heparin. Evidence is presented for the target of inositol phosphate being the catalytic subunit of the protein phosphatase. A parallelism is observed between the ability of the several inositol trisphosphates to activate the protein phosphatase and reported data indicating their ability to release calcium in permeabilized cells.