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Journal of Dairy Science Feb 1988An acid phosphatase has been partially purified from lactating bovine mammary gland. Properties of this enzyme were compared with those of a well-characterized...
An acid phosphatase has been partially purified from lactating bovine mammary gland. Properties of this enzyme were compared with those of a well-characterized phosphoprotein phosphatase from bovine spleen. The two enzymes were similar in their activation by sulfhydryl reagents and inhibition by metal chelating agents. Both enzymes rapidly hydrolyze ATP and aromatic phosphates and are relatively inactive toward alkyl phosphates; both are tartrate-resistant phosphatases. The mammary enzyme has a low Michaelis constant for alpha s1-casein (42 microM), and thus, like the spleen enzyme, appears to be a phosphoprotein phosphatase. Finally, the spleen and mammary enzymes displayed reactivity toward phosphotyrosine, a model substrate for phosphotyrosyl protein phosphatase. Thus, the phosphatases from spleen and mammary gland are quite similar in reactivity and could possibly be similar in function.
Topics: Acid Phosphatase; Animals; Cattle; Female; Lactation; Mammary Glands, Animal; Phosphoprotein Phosphatases; Phosphotyrosine; Pregnancy; Tyrosine
PubMed: 2454249
DOI: 10.3168/jds.S0022-0302(88)79560-0 -
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 -
European Journal of Biochemistry Oct 1981Phosphoprotein phosphatase IA, which represents the major glycogen synthase phosphatase activity in rat liver cytosol, has been purified to apparent homogeneity by...
Phosphoprotein phosphatase IA, which represents the major glycogen synthase phosphatase activity in rat liver cytosol, has been purified to apparent homogeneity by chromatography on DEAE-cellulose, histone - Sepharose-4B and Sephadex G-100. The molecular weight of the purified enzyme was 40 000 by gel filtration and 48 000 by sodium dodecyl sulfate gel electrophoresis, Phosphatase IA is therefore a monomeric protein. When treated with 80% ethanol at room temperature, phosphatase IA underwent an inactivation which was totally prevented by 2 mM MgCl2. Catalytically, phosphatase IA has a preference for glycogen synthase D compared with phosphatases IB and II and obligatorily requires Mg2+ or Mn2+ for activity. Maximum activity was attained at 5 mM MgCl2. Since Mg2+ does not activate other phosphoprotein phosphatases in rat liver cytosol, we propose the term 'Mg2+-dependent glycogen synthase phosphatase' for phosphatase IA.
Topics: Animals; Chromatography; Cytosol; Enzyme Activation; Glycogen-Synthase-D Phosphatase; Liver; Magnesium; Male; Phosphoprotein Phosphatases; Rats; Rats, Inbred Strains
PubMed: 6273162
DOI: 10.1111/j.1432-1033.1981.tb05636.x -
European Journal of Biochemistry Dec 1979A metal-ion-independent, nonspecific phosphoprotein phosphatase (Mr = 35000) which represents the major phosphorylase phosphatase activity in bovine adrenal cortex has...
A metal-ion-independent, nonspecific phosphoprotein phosphatase (Mr = 35000) which represents the major phosphorylase phosphatase activity in bovine adrenal cortex has been purified to apparent homogeneity. An alkaline phosphatase activity (p-nitrophenyl phosphate as a substrate) of the same molecular weight, which requires both a metal ion (Mg2+ greater than Mn2+ greater than Co2+) and a sulfhydryl compound for activity, has been found to co-purify with the phosphoprotein phosphatase throughout the purification procedures. Characterization of the phosphoprotein and the alkaline phosphatase activities with respect to their catalytic properties, substrate and metal ion specificities, relationship with large molecular forms of the enzymes and responses to various effectors has been carried out. The results indicate that the phosphoprotein phosphatase can be converted by pyrophosphoryl compounds (e.g. PPi and ATP) to a metal-ion-dependent form which, subsequently, can be reactivated by Co2+ greater than Mn2+ but not by Mg2+ or Zn2+. The results also indicate that, although the phosphoprotein and the alkaline phosphatase activities are closely associated, they exhibit distinct physical and catalytic properties. Discussions concerning whether these two activities represent two different forms of the same protein or two different yet very similar polypeptide chains have been presented.
Topics: Adrenal Cortex; Alkaline Phosphatase; Animals; Calcium; Cattle; Cobalt; Dithiothreitol; Kinetics; Magnesium; Manganese; Molecular Weight; Phosphoprotein Phosphatases; Phosphorylase Phosphatase
PubMed: 230963
DOI: 10.1111/j.1432-1033.1979.tb04251.x -
Physiological Reviews Jan 2004The protein serine/threonine phosphatase protein phosphatase-1 (PP1) is a ubiquitous eukaryotic enzyme that regulates a variety of cellular processes through the... (Review)
Review
The protein serine/threonine phosphatase protein phosphatase-1 (PP1) is a ubiquitous eukaryotic enzyme that regulates a variety of cellular processes through the dephosphorylation of dozens of substrates. This multifunctionality of PP1 relies on its association with a host of function-specific targetting and substrate-specifying proteins. In this review we discuss how PP1 affects the biochemistry and physiology of eukaryotic cells. The picture of PP1 that emerges from this analysis is that of a "green" enzyme that promotes the rational use of energy, the recycling of protein factors, and a reversal of the cell to a basal and/or energy-conserving state. Thus PP1 promotes a shift to the more energy-efficient fuels when nutrients are abundant and stimulates the storage of energy in the form of glycogen. PP1 also enables the relaxation of actomyosin fibers, the return to basal patterns of protein synthesis, and the recycling of transcription and splicing factors. In addition, PP1 plays a key role in the recovery from stress but promotes apoptosis when cells are damaged beyond repair. Furthermore, PP1 downregulates ion pumps and transporters in various tissues and ion channels that are involved in the excitation of neurons. Finally, PP1 promotes the exit from mitosis and maintains cells in the G1 or G2 phases of the cell cycle.
Topics: Animals; Cell Cycle; Cytoskeleton; Humans; Phosphoprotein Phosphatases; Phosphorylation; Protein Phosphatase 1; Stress, Physiological; Transcription, Genetic
PubMed: 14715909
DOI: 10.1152/physrev.00013.2003 -
The FEBS Journal Oct 2013Protein phosphatases, as the counterpart to protein kinases, are essential for homeostatic balance of cell signaling. Small chemical compounds that modulate the specific... (Review)
Review
Protein phosphatases, as the counterpart to protein kinases, are essential for homeostatic balance of cell signaling. Small chemical compounds that modulate the specific activity of phosphatases can be powerful tools to elucidate the biological functions of these enzymes. More importantly, many phosphatases are central players in the development of pathological pathways where inactivation can reverse or delay the onset of human diseases. Therefore, potent inhibitors for such phosphatases can be of great therapeutic benefit. In contrast to the seemingly identical enzymatic mechanism and structural characterization of eukaryotic protein kinases, protein phosphatases evolved from diverse ancestors, resulting in different domain architectures, reaction mechanisms and active site properties. In this review, we discuss for each family of serine/threonine protein phosphatases their involvement in biological processes and corresponding strategies for small chemical intervention. Recent advances in modern drug discovery technologies have markedly facilitated the identification of selective inhibitors for some members of the phosphatase family. Furthermore, the rapid growth in knowledge about structure-activity relationships related to possible new drug targets has aided the discovery of natural product inhibitors for the phosphatase family. This review summarizes the current state of investigation of the small molecules that regulate the function of serine/threonine phosphatases, the challenges presented and also strategies to overcome these obstacles.
Topics: Animals; Drug Design; Enzyme Inhibitors; Humans; Phosphoprotein Phosphatases; Structure-Activity Relationship
PubMed: 23937612
DOI: 10.1111/febs.12481 -
Molecular Cell Dec 2019Dynamic protein phosphorylation constitutes a fundamental regulatory mechanism in all organisms. Phosphoprotein phosphatase 4 (PP4) is a conserved and essential nuclear...
Dynamic protein phosphorylation constitutes a fundamental regulatory mechanism in all organisms. Phosphoprotein phosphatase 4 (PP4) is a conserved and essential nuclear serine and threonine phosphatase. Despite the importance of PP4, general principles of substrate selection are unknown, hampering the study of signal regulation by this phosphatase. Here, we identify and thoroughly characterize a general PP4 consensus-binding motif, the FxxP motif. X-ray crystallography studies reveal that FxxP motifs bind to a conserved pocket in the PP4 regulatory subunit PPP4R3. Systems-wide in silico searches integrated with proteomic analysis of PP4 interacting proteins allow us to identify numerous FxxP motifs in proteins controlling a range of fundamental cellular processes. We identify an FxxP motif in the cohesin release factor WAPL and show that this regulates WAPL phosphorylation status and is required for efficient cohesin release. Collectively our work uncovers basic principles of PP4 specificity with broad implications for understanding phosphorylation-mediated signaling in cells.
Topics: Amino Acid Sequence; Binding Sites; Conserved Sequence; Crystallography, X-Ray; HEK293 Cells; HeLa Cells; Humans; Phosphoprotein Phosphatases; Phosphorylation; Protein Binding; Substrate Specificity
PubMed: 31585692
DOI: 10.1016/j.molcel.2019.08.029 -
BMB Reports Apr 2020Protein phosphatase 4 (PP4), one of serine/threonine phosphatases, is involved in many critical cellular pathways, including DNA damage response (DNA repair, cell cycle... (Review)
Review
Protein phosphatase 4 (PP4), one of serine/threonine phosphatases, is involved in many critical cellular pathways, including DNA damage response (DNA repair, cell cycle regulation, and apoptosis), tumorigenesis, cell migration, immune response, stem cell development, glucose metabolism, and diabetes. PP4 has been steadily studied over the past decade about wide spectrum of physiological activities in cells. Given the many vital functions in cells, PP4 has great potential to develop into the finding of key working mechanisms and effective treatments for related diseases such as cancer and diabetes. In this review, we provide an overview of the cellular and molecular mechanisms by which PP4 impacts and also discuss the functional significance of it in cell health. [BMB Reports 2020; 53(4): 181-190].
Topics: Animals; Apoptosis; Cell Cycle Checkpoints; Cell Cycle Proteins; DNA Repair; Genomic Instability; Glucose; Humans; Immunity; Phosphoprotein Phosphatases
PubMed: 32192570
DOI: 10.5483/BMBRep.2020.53.4.019 -
Nature Communications Jan 2015The cell division cycle requires tight coupling between protein phosphorylation and dephosphorylation. However, understanding the cell cycle roles of multimeric protein...
The cell division cycle requires tight coupling between protein phosphorylation and dephosphorylation. However, understanding the cell cycle roles of multimeric protein phosphatases has been limited by the lack of knowledge of how their diverse regulatory subunits target highly conserved catalytic subunits to their sites of action. Phosphoprotein phosphatase 4 (PP4) has been recently shown to participate in the regulation of cell cycle progression. We now find that the EVH1 domain of the regulatory subunit 3 of Drosophila PP4, Falafel (Flfl), directly interacts with the centromeric protein C (CENP-C). Unlike other EVH1 domains that interact with proline-rich ligands, the crystal structure of the Flfl amino-terminal EVH1 domain bound to a CENP-C peptide reveals a new target-recognition mode for the phosphatase subunit. We also show that binding of Flfl to CENP-C is required to bring PP4 activity to centromeres to maintain CENP-C and attached core kinetochore proteins at chromosomes during mitosis.
Topics: Animals; Animals, Genetically Modified; Cell Cycle; Cells, Cultured; Centromere; Chromosomal Proteins, Non-Histone; Crystallography; Drosophila Proteins; Drosophila melanogaster; Electrophoretic Mobility Shift Assay; Image Processing, Computer-Assisted; Mass Spectrometry; Microscopy, Confocal; Mutagenesis, Site-Directed; Phosphoprotein Phosphatases; Protein Structure, Tertiary; RNA Interference
PubMed: 25562660
DOI: 10.1038/ncomms6894 -
Microbiology (Reading, England) Aug 2005Phosphoprotein phosphatases encoded by the prpA and prpB genes function in signal transduction pathways for degradation of misfolded proteins in the extracytoplasmic...
Phosphoprotein phosphatases encoded by the prpA and prpB genes function in signal transduction pathways for degradation of misfolded proteins in the extracytoplasmic compartments of Escherichia coli. In order to trace the evolution of prp genes and assess their roles in other enteric pathogens, the structure and distribution of these genes among closely related Shigella subgroups were studied. PCR amplification, probe hybridization studies and DNA sequencing were used to determine the prp genotypes of 58 strains from the four Shigella subgroups, Dysenteriae, Boydii, Sonnei and Flexneri. It was found that the prp alleles among Shigella subgroups were extremely susceptible to gene inactivation and that the mutations involved in prp allele inactivation were varied. They included IS insertions, gene replacement by an IS element, a small deletion within the gene or large deletion engulfing the entire gene region, and base substitutions that generated premature termination codons. As a result, of 58 strains studied, only eight (14 %) possessed intact prpA and prpB genes. Of the Shigella strains examined, 76 % (44/58) showed at least one of the prp alleles inactivated by one or more IS elements, including IS1, IS4, IS600 and IS629. Phylogenetic analysis revealed that IS elements have been independently acquired in multiple lineages of Shigella, suggesting that loss of functional alleles has been advantageous during Shigella strain evolution.
Topics: DNA Transposable Elements; Molecular Sequence Data; Phosphoprotein Phosphatases; Phylogeny; Shigella; Signal Transduction
PubMed: 16079345
DOI: 10.1099/mic.0.27990-0