Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.3.16 (calcineurin)
17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

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.
...
PMID:Polyamine stimulation of protein phosphatase-2A from rat liver using a non-protein phosphoester substrate. 304 Aug 20

We have characterized protein phosphorylation in vitro in subcellular fractions from Drosophila melanogaster heads. Optimal conditions for the incorporation of 32P into proteins, and its dependence on ATP, divalent cations, and cyclic nucleotides have been determined, as well as the effect of inhibitors of ATPase, protein phosphatase, and protein kinase on protein phosphorylation. Among these inhibitors, Zn2+ was found to affect the incorporation of 32P into specific bands and p-hydroxymercuribenzoate was found to be most suited for freezing the activity of both kinases and phosphatases. Cyclic AMP-dependent protein kinase (cAMP-dPK) activity was present in both supernatant (S2) and particulate (P2) fractions, with the majority (60-85%, depending on the homogenization medium) being associated with S2, as determined by phosphorylation of exogenous synapsin I. cAMP-dPK catalyzed the phosphorylation of at least 18 endogenous polypeptides in S2 and at least 10 endogenous polypeptides in P2. These proteins could be classified on the basis of the extent of stimulation of phosphorylation by cyclic nucleotides, dependence on cyclic nucleotide concentration, and rate of phosphorylation. A phosphoprotein of 51 kilodaltons (pp51) was a major component of the S2 and P2 fractions and displayed properties expected from the regulatory subunit of the cAMP-dPK, R-II. A phosphoprotein doublet of approximately 37 kilodaltons (pp37) was stimulated to the largest extent by cAMP in the P2 and S2 fractions. The phosphorylation of several proteins in both fractions was significantly lowered by the mammalian Walsh inhibitor of cAMP-dPK, whereas in some cases the stimulation of phosphorylation of the same proteins by exogeneous cAMP was relatively small. Phosphoproteins from two learning mutants known to be deficient in cAMP metabolism, dnc and rut, were analyzed for their extent of phosphorylation in the presence of a stable cAMP analogue; no significant differences from normal were detected, suggesting that the genetic defect in cAMP metabolism is not accompanied by constituent abnormalities in phosphorylated substrates in the adult fly, and that the physiological defects in these mutants result from aberrations in the interaction of the cAMP cascade with normal substrates. The majority of Ca2+/calmodulin kinase activity (80-90%, depending on the homogenization procedure) was associated with S2, as revealed by phosphorylation of exogenous synapsin I. Two endogenous substrates for this kinase in P2 had molecular masses of approximately 45 and 87 kilodaltons. At least 11 substrates for the Ca2+/calmodulin-dependent kinase were detected in S2.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:In vitro protein phosphorylation in head preparations from normal and mutant Drosophila melanogaster. 304 Sep 7

The complete amino acid sequence of bovine brain DARPP-32, a dopamine- and cyclic AMP-regulated neuronal phosphoprotein, which is a potent and specific inhibitor of the catalytic subunit of protein phosphatase-1, has been determined. The S-14C-carboxymethylated protein was subjected to enzymatic cleavage by endoproteinase Lys-C, endoproteinase Arg-C, trypsin, chymotrypsin, and Staphylococcus aureus V8 protease, and to chemical cleavage by cyanogen bromide. The overlapping sets of peptides were purified by high performance liquid chromatography and subjected to amino acid sequencing by automated Edman degradation to deduce the complete sequence. The protein consists of a single NH2-terminal blocked polypeptide chain of 202 residues, with a calculated molecular mass of 22,591 daltons, excluding the unidentified NH2-terminal blocking group. This molecular mass is significantly lower than earlier estimates based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis or hydrodynamic measurements. The threonine residue that is phosphorylated by cyclic AMP-dependent protein kinase (Hemmings, H. C., Jr., Williams, K. R., Konigsberg, W. H., and Greengard, P. (1984) J. Biol. Chem. 259, 14486-14490), and that must be phosphorylated for the expression of inhibitory activity, is located at position 34. The molecule contains only 1 cysteine residue and 1 tryptophan residue, at positions 72 and 161, respectively. DARPP-32 is very hydrophilic, and contains a stretch of 16 consecutive acidic residues from position 119 to 134. The predicted secondary structure suggests the presence of 47% alpha-helix, 7% beta-sheet, and 46% random coil, with 11 beta-turns. Comparison of the complete amino acid sequence of bovine DARPP-32 with that of rabbit skeletal muscle protein phosphatase inhibitor-1 revealed a significant amount of sequence identity in the NH2-terminal regions of these two proteins. The active region of inhibitor-1 has been localized to an NH2-terminal fragment (Aitken, A., and Cohen, P. (1982) FEBS Lett. 147, 54-58), the part of the molecule that is most similar to DARPP-32. These data suggest that these two protein phosphatase inhibitors may share a common structural basis for their inhibitory activity and may be related by a common ancestral gene.
...
PMID:DARPP-32, a dopamine- and cyclic AMP-regulated neuronal phosphoprotein. Primary structure and homology with protein phosphatase inhibitor-1. 351 Oct 54

Since it had been previously shown that in Paramecium cells exocytosis involves the dephosphorylation of a 65-kD phosphoprotein (PP), we tried to induce exocytotic membrane fusion by exogenous phosphatases (alkaline phosphatase or calcineurin [CaN]). The occurrence of calmodulin (CaM) at preformed exocytosis sites (Momayezi, M., H. Kersken, U. Gras, J. Vilmart-Seuwen, and H. Plattner, 1986, J. Histochem. Cytochem., 34:1621-1638) and the current finding of the presence of the 65-kD PP and of a CaN-like protein in cell surface fragments ("cortices") isolated from Paramecium cells led us to also test the effect of antibodies (Ab) against CaM or CaN on exocytosis performance. Microinjected anti-CaN Ab strongly inhibit exocytosis. (Negative results with microinjected anti-CaM Ab can easily be explained by the abundance of CaM.) Alternatively, microinjection of a Ca2+-CaM-CaN complex triggers exocytosis. The same occurs with alkaline phosphatase. All these effects can also be mimicked in vitro with isolated cortices. In vitro exocytosis triggered by adding Ca2+-CaM-CaN or alkaline phosphatase is paralleled by dephosphorylation of the 65-kD PP. Exocytosis can also be inhibited in cortices by anti-CaM Ab or anti-CaN Ab. In wild-type cells, compounds that inhibit phosphatase activity, but none that inhibit kinases or proteases, are able to inhibit exocytosis. Exocytosis cannot be induced by phosphatase injection in a membrane-fusion-deficient mutant strain (nd9-28 degrees C) characterized by a defective organization of exocytosis sites (Beisson, J., M. Lefort-Tran, M. Pouphile, M. Rossignol, and B. Satir, 1976, J. Cell Biol., 69:126-143). We conclude that exocytotic membrane fusion requires an adequate assembly of molecular components to allow for the dephosphorylation of a 65-kD PP and that this step is crucial for the induction of exocytotic membrane fusion in Paramecium cells. In vivo this probably involves a Ca2+-CaM-stimulated CaN-like PP phosphatase.
...
PMID:Exocytosis induction in Paramecium tetraurelia cells by exogenous phosphoprotein phosphatase in vivo and in vitro: possible involvement of calcineurin in exocytotic membrane fusion. 361 Nov 84

"Heavy" sarcoplasmic reticulum vesicles loaded with 5 mM CaCl2 in the presence of protease inhibitors were phosphorylated by addition of MgATP in the presence or absence of calmodulin. The major site of phosphorylation was a 60-kDa protein. In the absence of added calmodulin, phosphorylation of the 60-kDa protein reached its maximal value (8 pmol of P/mg of membrane protein) at 1 min. In the presence of 1 microM calmodulin, a 2-fold higher level of phosphorylation (16.1 pmol of P/mg of sarcoplasmic reticulum) was reached within a shorter time (10 s). The phosphoprotein was then spontaneously dephosphorylated. The initial rate of Ca2+ release, which was induced by a Ca2+ jump and determined by stopped-flow fluorometry using chlorotetracycline, decreased upon phosphorylation, whereas it was restored upon dephosphorylation. There was good correlation between the amount of P incorporation into the 60-kDa protein and the extent of inhibition of Ca2+ release. In the presence of added calmodulin the protein kinase activity sharply increased in the [Ca2+] range of 0.2-2 microM with a concentration for half-maximal activation at 0.6 microM. On the other hand, the protein phosphatase activity was virtually independent of calmodulin and [Ca2+] in the [Ca2+] range in which protein kinase was activated. The results suggest that the calmodulin-dependent phosphorylation of the 60-kDa protein plays an important role in the regulation of Ca2+ release from sarcoplasmic reticulum.
...
PMID:Involvement of 60-kilodalton phosphoprotein in the regulation of calcium release from skeletal muscle sarcoplasmic reticulum. 374 63

Stimulation of bovine chromaffin cell in culture changed (increased or decreased) the phosphorylation state of several proteins as examined by 32P incorporation. Enhanced phosphorylation of 22 protein bands as well as increased dephosphorylation of a 20.4 kilodaltons protein band was observed when extracts of cultured chromaffin cells stimulated by either acetylcholine or high K+ were subjected to mono-dimensional gel electrophoresis. For several protein bands, the degree of phosphorylation was larger in cells stimulated by acetylcholine than in those challenged by a depolarizing concentration of K+. The most affected phosphoproteins have apparent molecular weights of 14,800, 29,000, 33,000, 57,000 (tubulin subunit), 63,000 (tyrosine hydroxylase subunit) and 94,000. The presence of a low extracellular calcium concentration (0.5 mM Ca2+ plus 15 mM Mg2+) in the incubation medium inhibited (38-100%) the acetylcholine-evoked increases in protein phosphorylation observed previously for 18 protein bands. Trifluoperazine at the concentration required for 50% inhibition of acetylcholine-induced catecholamine release decreases (33-100%) the stimulation-induced phosphorylation in all polypeptides, with the exception of the 14.8 kilodaltons and the dephosphorylated 20.4 kilodaltons components which were not affected. Two-dimensional gel electrophoresis analysis revealed that exposure of chromaffin cells to acetylcholine produced two types of effect on protein phosphorylation: activation of protein kinase activities affecting about 30 polypeptides; activation of protein phosphatase activities resulting in the dephosphorylation of about 40 polypeptides, most of them appearing as minor phosphoproteins, with the exception of the alpha-subunit of pyruvate dehydrogenase and the 20.4 kilodaltons polypeptide. On the basis of their molecular properties (molecular weight and pI) and their abundance in chromaffin cells, the 80 kilodaltons phosphoprotein which focused at pI 4.8 and the 117.5 kilodaltons phosphoprotein which focused at pI 5.0 were identified as chromogranins A and B, respectively. The relationship between acetylcholine-induced protein phosphorylation (or dephosphorylation) and catecholamine secretion was also investigated. The time course of protein phosphorylation (or dephosphorylation) paralleled or preceded [3H]noradrenaline release for 16 phosphoproteins.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Phosphorylation and dephosphorylation of chromaffin cell proteins in response to stimulation. 377 57

When an M-phase promoting factor (MPF) is injected into Xenopus oocytes, which are naturally arrested at the G2/prophase boundary, it induces rapid entry of the cells into M-phase. MPF is present in late G2 and in M-phase of a variety of cell types, such as Xenopus eggs (naturally arrested in M), cleaving embryos, yeast, HeLa, and CHO cultures. MPF has been purified approximately 50-fold from eggs. It is stabilized by gamma-thio-ATP and by phosphoprotein phosphatase inhibitors. It runs as a protein of approximately 100 kd size on gel filtration. Oocytes contain a precursor of MPF, which is activated by post-translational means when a small amount of purified MPF is injected into the cell. Thus, MPF appears to be an auto-activating cytoplasmic trigger of M-phase. At anaphase of the cell cycle, MPF is inactivated due to the appearance of an 'anti-MPF' activity. Monoclonal antibodies have been prepared to partially purified MPF stabilized by gamma-thio-ATP, and several preparations which inactivate MPF were obtained. The antibodies are directed against thio-phosphate groups carried by a set of proteins including MPF. This indicates that MPF is present in our active preparations as a thio-phosphoprotein. These and other data suggest that MPF is normally activated in the cell cycle by a phosphorylation reaction.
...
PMID:M-phase promoting factors from eggs of Xenopus laevis. 390

Four phosphoprotein phosphatases, with the ability to act upon hydroxymethylglutaryl (HMG)-CoA reductase, phosphorylase, and glycogen synthase have been purified from rat liver cytosol through a process that involves DEAE-cellulose, aminohexyl-Sepharose-4B, and Bio-Gel A 1.5 m chromatographies. Protein phosphatase II (Mr 180,000) was the major enzyme (68%) with a very broad substrate specificity, showing similar activity toward the three substrates. Phosphatases I1 (Mr 180,000) and I3 (Mr 250,000) accounted for only 12 and 15% of the total activity, respectively, and they were also able to dephosphorylate the three substrates. In contrast, phosphatase I2 (Mr 200,000) showed only phosphorylase phosphatase activity with insignificant dephosphorylating capacity toward HMG-CoA reductase and glycogen synthase. Upon ethanol treatment at room temperature, the Mr of all phosphatases changed; protein phosphatases I2, I3, and II were brought to an Mr of 35,000, while phosphatase I1 was reduced to an Mr of 69,000. Glycogen synthase phosphatase activity was decreased in all four phosphatases. There was also a decrease in phosphatase I1 activity toward HMG-CoA reductase and phosphorylase as substrates. The HMG-CoA reductase phosphatase and phosphorylase phosphatase activities of phosphatases I2, I3, and II were increased after ethanol treatment. Each protein phosphatase showed a different optimum pH, which changed depending on the substrate. The four phosphatases increased their activity in the presence of Mn2+ and Mg2+. In general, Mn2+ was a better activator than Mg2+, and phosphatase I1 showed a stronger dependency on these cations than any other phosphatase. Phosphorylase was a competitive substrate in the HMG-CoA reductase phosphatase and glycogen synthase phosphatase reactions of protein phosphatases I1, I3, and II. HMG-CoA reductase was also able to compete with phosphorylase and glycogen synthase for phosphatase activity. Glycogen synthase phosphatase activity presented less inhibition in the low-Mr forms. A comparison has been made with other protein phosphatases previously reported in the literature.
...
PMID:Modulation of rat liver hydroxymethylglutaryl-CoA reductase by protein phosphatases: purification of nonspecific hydroxymethylglutaryl-CoA reductase phosphatases. 397 May 34

To investigate the alterations of phosphoseryl/phosphothreonyl-protein phosphatases in neoplastic tissues, the cytosols of rat liver and AH-13, a strain of rat ascites hepatoma, were chromatographed on DEAE-cellulose and the fractions obtained were assayed for protein phosphatase with glycogen synthase D and phosphorylase alpha as phosphoprotein substrates. While the glycogen synthase phosphatase and phosphorylase phosphatase activities of liver cytosol were largely due to phosphatases IA and II, respectively, as previously reported, these phosphatases were absent or present in only small amounts in AH-13 cytosol, whose glycogen synthase phosphatase and phosphorylase phosphatase activities were due almost wholly to a novel protein phosphatase that appeared to be absent in liver. This phosphatase, termed phosphatase H, was purified further by aminohexyl-Sepharose-4B and Sephadex G-200 chromatography without altering its glycogen synthase D/phosphorylase alpha activity ratio. Purified phosphatase H required Mg2+ or Mn2+ for activity and had a molecular weight of about 330,000. It displayed a substrate specificity broader than that of either phosphatase IA or II.
...
PMID:Cytosolic protein phosphatases of rat ascites hepatoma AH-13 as compared with those of rat liver: isolation and characterization of a novel protein phosphatase. 608 36

The neurotransmitter dopamine has been demonstrated by biochemical, histochemical and immunocytochemical techniques to be unevenly distributed in the mammalian central nervous system. DARPP-32 (dopamine- and cyclic-AMP-regulated phosphoprotein of molecular weight 32,000) is a neuronal phosphoprotein that displays a regional distribution in the mammalian brain very similar to that of dopamine-containing nerve terminals, being highly concentrated in the basal ganglia. The state of phosphorylation of DARPP-32 can be regulated by dopamine and by cyclic AMP in intact nerve cells, suggesting a role for this phosphoprotein in mediating certain of the effects of dopamine on dopaminoceptive cells. The observation that many of the physical and chemical properties of purified DARPP-32 resemble those of phosphatase inhibitor-1 (inhibitor-1), a widely distributed inhibitor of protein phosphatase-1, suggests that DARPP-32 might also function as a phosphatase inhibitor. We report here that DARPP-32 inhibits protein phosphatase-1 at nanomolar concentrations. Moreover, like inhibitor-1, DARPP-32 is effective as an inhibitor in its phosphorylated but not its dephosphorylated form. Thus, the basal ganglia of mammalian brain contain a region-specific neuronal phosphoprotein that is a protein phosphatase inhibitor.
...
PMID:DARPP-32, a dopamine-regulated neuronal phosphoprotein, is a potent inhibitor of protein phosphatase-1. 608 60


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---