title: Polyamine stimulation of protein phosphatase-2A from rat liver using a non-protein phosphoester substrate.
abstract: The polyamines, spermine and spermidine, activate a high molecular weight form of phosphorylase a phosphatase isolated from rat liver. This broad specificity protein phosphatase (type 2A) was partially purified, using both protein and non-protein phosphoester substrates. Spermine and spermidine activated isolated protein phosphatase-2A1 (apparent Mr 210,000) approximately 2-fold, when p-nitrophenyl phosphate (PNPP) was used as substrate. Freeze-thawing, which activated the phosphatase activity against a variety of phosphoprotein substrates, also increased the extent of stimulation of PNPP phosphatase activity by spermine (8 to 9-fold with Ka of 93 microM) and spermidine (6 to 7-fold with Ka 280 microM). Kinetic analysis indicated that the activation of phosphatase by polyamines was accomplished by an increase in Vmax of the enzyme, by a mechanism independent of that achieved by other cations. The data indicate that polyamines, at physiological concentrations, can activate a form of protein phosphatase widely distributed in mammalian tissues, and thereby influence cellular protein phosphorylation.
mesh_terms: D000818:Animals; D002845:Chromatography; D004789:Enzyme Activation / Q000187:drug effects; D005615:Freezing; D006358:Hot Temperature; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008297:Male; D009596:Nitrophenols / Q000378:metabolism*; D009943:Organophosphorus Compounds / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000302:isolation & purification / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D011073:Polyamines / Q000494:pharmacology*; D054648:Protein Phosphatase 2; D051381:Rats; D011919:Rats, Inbred Strains; D013095:Spermidine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology
chemical_list: D009596:Nitrophenols; D009943:Organophosphorus Compounds; D010750:Phosphoproteins; D011073:Polyamines; D013096:Spermine; C008644:nitrophenylphosphate; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D013095:Spermidine