title: The protein phosphatases involved in cellular regulation. 1. Modulation of protein phosphatases-1 and 2A by histone H1, protamine, polylysine and heparin.
abstract: The phosphorylase phosphatases in rat and rabbit liver cytosol that are markedly stimulated by histone H1, protamine and polylysine were identified as protein phosphatases-2A0, 2A1 and 2A2 by anion-exchange chromatography, gel-filtration and immunotitration experiments. Histone H1 and protamine also stimulated the dephosphorylation of phosphorylase kinase, glycogen synthase, fructose-1,6-bisphosphatase, pyruvate kinase, acetyl-CoA carboxylase and phenylalanine hydroxylase by phosphatases-2A1 and 2A2, and with several of these substrates activation was even more striking (20-100-fold) than that observed with phosphorylase (approximately 5-fold). Activation by basic polypeptides did not involve dissociation of these phosphatases to the free catalytic subunit. The dephosphorylation of phosphorylase by protein phosphatase-1 was suppressed by basic polypeptides, protamine and polylysine being the most potent inhibitors. However, the dephosphorylation of glycogen synthase, pyruvate kinase and acetyl-CoA carboxylase were markedly stimulated by histone H1 and protamine (2-13-fold). Consequently, with the appropriate substrates, protein phosphatase-1 can also be regarded as a basic-polypeptide-activated protein phosphatase. Heparin stimulated (1.5-2-fold) the dephosphorylation of phosphorylase by phosphatases-2A0 and 2A1, provided that Mn2+ was present, but phosphatase-2A2 and the free catalytic subunit of phosphatase-2A were unaffected. Heparin, in conjunction with Mn2+, also stimulated (1.5-fold) the dephosphorylation of glycogen synthase (labelled in sites 3 abc), phosphorylase kinase and phenylalanine hydroxylase by phosphatase-2A1, but not by phosphatase-2A2. By contrast, the dephosphorylation of phosphorylase and phosphorylase kinase by protein phosphatase-1 was inhibited by heparin. However, dephosphorylation of glycogen synthase and pyruvate kinase by phosphatase-1 was stimulated by this mucopolysaccharide. The studies demonstrate that basic proteins can be used to distinguish protein phosphatase-1 from protein phosphatase-2A, but only if phosphorylase is employed as substrate. Optimal differentiation of the two phosphatases is observed at 30 micrograms/ml protamine or at heparin concentrations greater than 150 microM.
authors.forename: S
authors.initials: S
authors.lastname: Pelech
authors.forename: P
authors.initials: P
authors.lastname: Cohen
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D006493:Heparin / Q000494:pharmacology*; D006657:Histones / Q000494:pharmacology*; D008099:Liver / Q000201:enzymology*; D010455:Peptides / Q000494:pharmacology*; D010749:Phosphoprotein Phosphatases / Q000502:physiology*; D010765:Phosphorylase Phosphatase / Q000502:physiology*; D011107:Polylysine / Q000494:pharmacology*; D011479:Protamines / Q000494:pharmacology*; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D006657:Histones; D010455:Peptides; D011479:Protamines; D011107:Polylysine; D006493:Heparin; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; D010765:Phosphorylase Phosphatase