title: Purification and properties of a protein inhibitor that inhibits phosphatase 2A activity when hydroxymethylglutaryl coenzyme A reductase is the substrate.
abstract: A heat-stable protein inhibitor of the hydroxymethylglutaryl-CoA reductase phosphatase 2A activity has been identified and purified to homogeneity, as judged by polyacrylamide gel electrophoresis. The apparent molecular mass was 20,000 Da. The protein lost its inhibitory properties when incubated with trypsin or treated with ethanol. The inhibitor protein does not inhibit type 1 phosphatase when either phosphorylase or hydroxymethylglutaryl-CoA reductase is the substrate. In contrast, this protein inhibitor inhibits the rat liver type 2A phosphatase activity when hydroxymethylglutaryl-CoA reductase is the substrate but not when phosphorylase a is the substrate. The inhibitor protein is not activated by incubation with ATP and cyclic AMP-dependent protein kinase and it is not phosphorylated by glycogen synthase kinase-3. These results, together with those of the kinetic experiments, suggest that the reductase phosphatase inhibitor is distinct from protein phosphatase inhibitor-1 and inhibitor-2.
authors.affiliation: Unit of Biochemistry, School of Pharmacy, University of Barcelona, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Serra
authors.forename: G
authors.initials: G
authors.lastname: Asins
authors.forename: V E
authors.initials: VE
authors.lastname: Calvet
authors.forename: F G
authors.initials: FG
authors.lastname: Hegardt
mesh_terms: D000818:Animals; D002384:Catalysis; D006358:Hot Temperature; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D008297:Male; D009124:Muscle Proteins / Q000302:isolation & purification* / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D011500:Protein Synthesis Inhibitors / Q000302:isolation & purification* / Q000494:pharmacology; D011506:Proteins / Q000302:isolation & purification* / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D013379:Substrate Specificity; D000097847:Protein Phosphatase Inhibitory Proteins
chemical_list: D006903:Hydroxymethylglutaryl CoA Reductases; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D009124:Muscle Proteins; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D011500:Protein Synthesis Inhibitors; D011506:Proteins; C024833:protein phosphatase inhibitor-2; D000097847:Protein Phosphatase Inhibitory Proteins