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Biochimica Et Biophysica Acta Aug 1978A protein phosphatase activity has been demonstrated in nuclei of rat ventral prostate utilizing 32P-labelled phosvitin as a model acidic phosphoprotein substrate. This...
A protein phosphatase activity has been demonstrated in nuclei of rat ventral prostate utilizing 32P-labelled phosvitin as a model acidic phosphoprotein substrate. This phosphoprotein phosphatase has a pH optimum of 6.7, is unaffected by the sulphydryl protecting agent 2-mercaptoethanol, and requires a divalent cation for maximal activity. Of the various divalent cations tested, Mg2+ is the most effective in reactivating the EDTA-inhibited enzyme. The phosphatase is inhibited by sodium flouride, sodium oxalate, N-ethylmaleimide, ATP and ADP but is relatively insensitive to ammonium molybdate. Increased ionic strength of the reaction medium also causes a reduction in the enzyme activity, e.g., by 48% at 200 mM sodium chloride. The activity of the acidic phosphoprotein phosphatase did not change significantly at 48 h or 96 h post-orchiectomy when expressed per unit of nuclear protein. However, it is reduced by approx. 30% at these times after castration if based on DNA content. The decline in activity per nucleus reflects the decrease in the realtive nuclear protein content observed at 48 h or 96 h post-orchiectomy. This suggests that the decline in the phosphorylation of prostatic nuclear acidic proteins which occurs upon androgen withdrawal is not due to increased nuclear phosphatase activity.
Topics: Androgens; Animals; Castration; Cell Nucleus; Kinetics; Magnesium; Male; Nucleoproteins; Phosphoprotein Phosphatases; Phosvitin; Prostate; Protein Kinases; Rats; Testis
PubMed: 208647
DOI: 10.1016/0304-4165(78)90227-1 -
ACS Chemical Biology Jan 2013Protein phosphatases have both protective and promoting roles in the etiology of diseases. A prominent example is the existence of oncogenic as well as tumor-suppressing... (Review)
Review
Protein phosphatases have both protective and promoting roles in the etiology of diseases. A prominent example is the existence of oncogenic as well as tumor-suppressing protein phosphatases. A few protein phosphatase activity modulators are already applied in therapies. These were however not developed in target-directed approaches, and the recent discovery of phosphatase involvement followed their application in therapy. Nevertheless, these examples demonstrate that small molecules can be generated that modulate the activity of protein phosphatases and are beneficial for the treatment of protein phosphorylation diseases. We describe here strategies for the development of activators and inhibitors of protein phosphatases and clarify some long-standing misconceptions concerning the druggability of these enzymes. Recent developments suggest that it is feasible to design potent and selective protein phosphatase modulators with a therapeutic potential.
Topics: Drug Delivery Systems; Humans; Phosphoprotein Phosphatases; Small Molecule Libraries
PubMed: 23214403
DOI: 10.1021/cb300597g -
Archives of Biochemistry and Biophysics Feb 2018Intracellular signal transduction is built on the basis of the subtle balance between phosphorylation and dephosphorylation. Ca/calmodulin-dependent protein kinase... (Review)
Review
Intracellular signal transduction is built on the basis of the subtle balance between phosphorylation and dephosphorylation. Ca/calmodulin-dependent protein kinase phosphatase (CaMKP/PPM1F/POPX2) and CaMKP-N (PPM1E/POPX1) are Ser/Thr phosphatases that belong to the PPM (protein phosphatase, Mg/Mn-dependent) family. The former was discovered in rat brain as a novel protein phosphatase regulating Ca/calmodulin-dependent protein kinases (CaMKs), whereas the latter was first identified in human cDNA databases using the rat CaMKP sequence. Subsequent studies have revealed that they are involved in various cellular functions through regulation of not only CaMKs but also other protein kinases such as AMP-activated protein kinase. Furthermore, accumulating evidence shows possible involvement of CaMKP and CaMKP-N in the pathogenesis of various diseases including cancer. Therefore, the biochemistry of CaMKP and CaMKP-N largely contributes to molecular medicine targeting these phosphatases. In this review, we summarized recent progress in the enzymology and biology of CaMKP and CaMKP-N. We also focused on etiology studies in which CaMKP and CaMKP-N are involved. Based on the emerging evidence, future perspectives of studies on these phosphatases and related issues to be elucidated are discussed.
Topics: Amino Acid Sequence; Animals; Calcium; Catalytic Domain; DNA, Complementary; Disease; Humans; Phosphoprotein Phosphatases; Protein Phosphatase 2C; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Signal Transduction
PubMed: 29317228
DOI: 10.1016/j.abb.2018.01.001 -
Molecular Microbiology Feb 2022Members of the Actinobacteria, including mycobacteria and streptomycetes, exhibit a distinctive mode of polar growth, with cell wall synthesis occurring in zones at cell...
Members of the Actinobacteria, including mycobacteria and streptomycetes, exhibit a distinctive mode of polar growth, with cell wall synthesis occurring in zones at cell poles and directed by the essential cell polarity determinant DivIVA. Streptomyces coelicolor modulates polar growth via the Ser/Thr protein kinase AfsK, which phosphorylates DivIVA. Here, we show that the phosphoprotein phosphatase SppA has strong effects on polar growth and cell shape and that it reverses the AfsK-mediated phosphorylation of DivIVA. SppA affects hyphal branching and the rate of tip extension. The sppA mutant hyphae also exhibit a high frequency of spontaneous growth arrests, indicating problems with maintenance of tip extension. The phenotypic effects are partially suppressed in an afsK sppA double mutant, indicating that AfsK and SppA to some extent share target proteins. Strains with a nonphosphorylatable mutant DivIVA confirm that the effect of afsK on hyphal branching during normal growth is mediated by DivIVA phosphorylation. However, the phenotypic effects of sppA deletion are independent of DivIVA phosphorylation and must be mediated via other substrates. This study adds a PPP-family protein phosphatase to the proteins involved in the control of polar growth and cell shape determination in S. coelicolor.
Topics: Bacterial Proteins; Cell Polarity; Hyphae; Phosphoprotein Phosphatases; Streptomyces coelicolor
PubMed: 34862689
DOI: 10.1111/mmi.14856 -
Biochimica Et Biophysica Acta Mar 1978Phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) from bovine tracheal smooth muscle extracts was isolated and its activity determined using two...
Phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) from bovine tracheal smooth muscle extracts was isolated and its activity determined using two [32P]phosphorylated proteins as substrates, i.e. phosphorylated histone (H-P) and a phosphorylated muscle specific substrate protein (MS-P) for the tracheal smooth muscle protein kinase. The enzyme was purified by the use of DEAE-cellulose followed by a two stage chromatography on a histone-Sepharose affinity column. Elution from the affinity column resolved the phosphoprotein phosphatase into four activity fractions. While fractions expressed phosphatase activity against both tested substrates the relative amounts of either activity varied. The ratio of activity towards H-P to activity towards MS-P changed from 11.5 to 0.12. The characterization of four phosphoprotein phosphatase fractions was based on the differences found in the following parameters: substrate specificity; sensitivity to NaF; influences of nucleotides (ATP, 5'-AMP, cyclic AMP, cyclic GMP) and the requirement of Mn2+ for maximal activity. Mg2+, Ba2+ or Ca2+ could not substitute for Mn2+.
Topics: Animals; Cations, Divalent; Cattle; Isoenzymes; Kinetics; Muscle, Smooth; Phosphoprotein Phosphatases; Substrate Specificity; Trachea
PubMed: 204354
DOI: 10.1016/0005-2744(78)90015-3 -
Journal of Biochemistry Mar 1981Plasma membrane isolated from rat liver contained activities of phosphoprotein phosphatase dephosphorylating [32P]phosphorylase a or [32P]phosphohistone. The properties...
Plasma membrane isolated from rat liver contained activities of phosphoprotein phosphatase dephosphorylating [32P]phosphorylase a or [32P]phosphohistone. The properties of the membrane-bound phosphatase were examined using these exogenous substrates. The optimal reaction rate was at pH near neutrality. At concentrations as low as 0.1-1.0 mM, Mg2+ or Mn2+ slightly stimulated the activity for phosphorylase a or phosphohistone, respectively; at higher concentrations, they were inhibitory with both substrates. Co2+ was inhibitory with both substrates, while Ca2+ had no significant effect. The phosphatase activities were inhibited by ATP, ADP, or AMP; the extents of inhibition were in opposite order with the two substrates. Phosphorylase phosphatase activity was strongly inhibited by KF or Pi. Phosphorylase phosphatase activity could be completely solubilized by incubating the membrane with 0.5 M NaCl or trypsin, and this was associated with several-fold activation. While Vmax values were increased, Km values for phosphorylase a were not much affected by these treatments. Unlike the soluble phosphatase, freezing in the presence of mercaptoethanol or by precipitation with ethanol failed to activate or to solubilize the membrane-bound phosphatase. The molecular weights of the NaCl-and the trypsin-solubilized phosphatase were estimated on gel filtration to be about 42,000 and 32,000, respectively. The present results indicate that the phosphoprotein phosphatase associated with liver plasma membrane shares several properties in common with phosphatases from other sources reported, and that, like those in the soluble fraction, it may be bound to some inhibitory proteins.
Topics: Animals; Cell Membrane; Enzyme Activation; Liver; Phosphoprotein Phosphatases; Phosphorylase Phosphatase; Rats; Solubility
PubMed: 6270067
DOI: 10.1093/oxfordjournals.jbchem.a133253 -
Biochemistry and Cell Biology =... Jul 1987Intact washed spermatozoa from goat cauda epididymis possess an ecto-phosphoprotein phosphatase that causes dephosphorylation of phosphoserine and phosphothreonine...
Intact washed spermatozoa from goat cauda epididymis possess an ecto-phosphoprotein phosphatase that causes dephosphorylation of phosphoserine and phosphothreonine residues of exogenous 32P-labelled histones. The cell-bound ecto-enzyme has high affinity for proteins (histones, casein, phosvitin, and protamine) rather than phosphate esters, such as p-nitrophenyl phosphate, beta-glycerophosphate, AMP, and ATP. The activity of the enzyme is inhibited by 4 mM Mg2+, Ca2+, Mn2+, or Co2+. Pi (10 mM), NaF (10 mM), and Zn2+ (1 mM) inhibit the enzyme by approximately 50, 35, and 100%, respectively. Polyamines such as spermine and spermidine at 10 mM each caused significant inhibition (60 and 30%, respectively) of the cell-bound phosphoprotein phosphatase activity, whereas cAMP, orthovanadate, and calmodulin (with or without Ca2+) had no appreciable effect. Under the standard assay conditions, spermatozoa remain intact as evidenced by assay of cytosolic enzyme markers. Both the washed and "native" intact spermatozoa showed nearly the same specific activity of the ectoenzyme. The product of the reaction (Pi) was found in the extracellular medium. Sonication doubled the enzymic activity of the intact cells. The specific activity of the enzyme was nearly fourfold higher in the intact forwardly motile cells than the "composite" spermatozoa. These data provide further support for the localization of a phosphoprotein phosphatase on the external surface of spermatozoa and that the ectoenzyme may have a role in the regulation of flagellar motility.
Topics: Animals; Cations, Divalent; Epididymis; Goats; Kinetics; Male; Phosphoprotein Phosphatases; Phosphoserine; Phosphothreonine; Polyamines; Spermatozoa; Substrate Specificity
PubMed: 2829947
DOI: 10.1139/o87-080 -
Trends in Biochemical Sciences Feb 2010The PP2C family serine/threonine phosphatase WIP1 is characterized by distinctive oncogenic properties mediated by inhibitory functions on several tumor suppressor... (Review)
Review
The PP2C family serine/threonine phosphatase WIP1 is characterized by distinctive oncogenic properties mediated by inhibitory functions on several tumor suppressor pathways, including ATM, CHK2, p38MAPK and p53. PPM1D, the gene encoding WIP1, is aberrantly amplified in different types of human primary cancers, and its deletion in mice results in a profound tumor-resistant phenotype. Numerous downstream targets of WIP1 have been identified, and genetic studies confirm that some play a part in tumorigenesis. Recent evidence highlights a new role for WIP1 in the regulation of a cell-autonomous decline in proliferation of certain self-renewing cell types, including pancreatic beta-cells, with advancing age. These emerging functions of WIP1 make it a potent therapeutic target against cancer and aging.
Topics: Aging; Animals; Humans; Neoplasms; Phosphoprotein Phosphatases; Protein Phosphatase 2C
PubMed: 19879149
DOI: 10.1016/j.tibs.2009.09.005 -
Biochimica Et Biophysica Acta.... Jan 2019Mammalian haloacid dehalogenase (HAD)-type phosphatases have evolved to dephosphorylate a wide range of small metabolites, but can also target macromolecules such as... (Review)
Review
Mammalian haloacid dehalogenase (HAD)-type phosphatases have evolved to dephosphorylate a wide range of small metabolites, but can also target macromolecules such as serine/threonine, tyrosine-, and histidine-phosphorylated proteins. To accomplish these tasks, HAD phosphatases are equipped with cap domains that control access to the active site and provide substrate specificity determinants. A number of capped HAD phosphatases impact protein phosphorylation, although structural data are consistent with small metabolite substrates rather than protein substrates. This review discusses the structures, functions and disease implications of the three closely related, capped HAD phosphatases pyridoxal phosphatase (PDXP or chronophin), phosphoglycolate phosphatase (PGP, also termed AUM or glycerol phosphatase) and phospholysine phosphohistidine inorganic pyrophosphate phosphatase (LHPP or HDHD2B). Evidence in support of small metabolite and protein phosphatase activity is discussed in the context of the diversity of their biological functions.
Topics: Actin Cytoskeleton; Animals; Humans; Hydrolases; Inorganic Pyrophosphatase; Neoplasms; Phosphoprotein Phosphatases; Phosphoric Monoester Hydrolases; Phosphorylation; Protein Tyrosine Phosphatases
PubMed: 30030002
DOI: 10.1016/j.bbamcr.2018.07.007 -
Biochimica Et Biophysica Acta Mar 1983Three peaks of protein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) activity (fractions a, b and c) acting on muscle phosphorylase...
Three peaks of protein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) activity (fractions a, b and c) acting on muscle phosphorylase (1,4-alpha-D-glucan:orthophosphate alpha-D-glucosyltransferase, EC 2.4.1.1) were separated by DEAE-cellulose chromatography of yeast extracts. In contrast to fractions a and b, only fraction c was able to liberate phosphate from 32P-labelled inactivated yeast phosphorylase. The activity of fraction c on both substrates was totally dependent on the presence of bivalent metal ions (Mg2+, Mn2+), and was activated by Mg . ATP. Following freezing in the presence of mercaptoethanol, fractions a and b were also able to dephosphorylate yeast phosphorylase. Rabbit muscle phosphoprotein phosphatase inhibitors 1 and 2 showed that yeast phosphatases acting on muscle phosphorylase were inhibited by inhibitor 2 but not by inhibitor 1. The action of fraction c on yeast phosphorylase was not inhibited by either inhibitor. The native yeast phosphorylase phosphatase (EC 3.1.3.17) was purified 8000-fold by ion-exchange chromatography, casein-Sepharose chromatography and Sephadex G-200 gel filtration. The purified enzyme was unable to dephosphorylate rabbit muscle phosphorylase a, but acted on casein phosphate (Km 3.3 mg/ml). Molecular weight was estimated to be 78 000 and pH optimum 6.5-7.5. Activity of the enzyme was dependent on bivalent metal ions (Mg2+, Mn2+) and was inhibited by fluoride (Ki 20 mM) and succinate (Ki 10 mM).
Topics: Kinetics; Magnesium; Manganese; Molecular Weight; Phosphoprotein Phosphatases; Phosphorylase Phosphatase; Saccharomyces cerevisiae
PubMed: 6299361
DOI: 10.1016/0167-4838(83)90392-8