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

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

Protein phosphatase 1, one of four major protein phosphatases involved in cellular regulation, was phosphorylated in vitro by pp60v-src, the transforming gene product of Rous sarcoma virus. Phosphorylation was accompanied by a loss of protein phosphatase activity. The inactivation of protein phosphatase 1 was time-dependent and the extent of inactivation correlated closely with the stoichiometry of phosphorylation. Under optimal conditions, 0.34 +/- 0.01 mol of phosphate were incorporated per mol of protein phosphatase and the activity of the enzyme was decreased by 39 +/- 2%. The inactivation required the presence of both MgATP and pp60v-src. There was no loss of activity when adenosine 5'-[beta gamma-imido]triphosphate was used in place of ATP. Phosphorylation of protein phosphatase 1 occurred exclusively on tyrosine residues and was blocked by specific antibodies to pp60v-src. During preincubation of pp60v-src at 41 degrees C, its protein kinase activity towards casein was lost rapidly. The ability of pp60v-src to phosphorylate and inactivate protein phosphatase 1 declined in parallel with the loss of casein kinase activity. Limited chymotryptic digestion of 32P-labeled protein phosphatase 1 (Mr 37,000) resulted in its quantitative conversion to a Mr 33,000 species. Conversion to this species was accompanied by the loss of 32P-labeling and by reactivation of the protein phosphatase. When various concentrations of chymotrypsin were used in the digestion, there was a close correlation between conversion to the Mr 33,000 species and the restoration of protein phosphatase activity. pp60v-src was unable to phosphorylate or inactivate a partially proteolyzed species of protein phosphatase 1 (Mr 33,000/34,000).
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PMID:Phosphorylation and inactivation of protein phosphatase 1 by pp60v-src. 300 27

Individual molecular forms of phosphoprotein phosphatase (PPase) and their inhibitors of the protein nature were isolated from rat heart muscle by means of column chromatography on DEAE Sephadex A-50. All the three fractions of PPase were capable to dephosphorylate casein but did not affect pyrophosphate. PPase I dephosphorylated trimethaphosphate or casein. The enzyme molecular forms were different from each other by the value of specific activity and sensitivity to heat treatment. Two protein inhibitors eluted by buffers of different ionic strength - 0.2 M and 1.6 M - were identified. One of them was inactivated during heat treatment (95 degrees 5 min), while the second inhibitor maintained completely its activity in these conditions.
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PMID:[Phosphoprotein phosphatase of the myocardium. Isolation of individual molecular forms and their regulation]. 300 34

Protein phosphatase activity towards endogenous nuclear substrates in sonicates of isolated nuclei was activated 2-4-fold by spermine. Exogenous casein was dephosphorylated by these preparations only in the presence of spermine. Activation by spermine was half maximal at about 0.1 mM. Spermidine also activated, with half maximal stimulation at 1mM; putrescine activated poorly. Mg++ and Ca++ appeared to activate the same phosphatase activity but were only 50% as effective as spermine. Spermine activation was inhibited by 200 mM NaCl, 50 mM NaF, or 40 mM beta-glycerol phosphate. Nuclear phosphatase activity, with or without spermine, was inhibited 50% by inhibitor 2 of protein phosphatase 1. These observations suggest that protein phosphatase 1 is a major nuclear protein phosphatase and that its activity against endogenous nuclear substrates is activated by physiological concentrations of spermine.
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PMID:Polyamine-activated protein phosphatase activity in HeLa cell nuclei. 300 89

Immunoaffinity purified pp60v-src was found to activate the MgATP-dependent protein phosphatase in the presence of MgATP. Although preliminary evidence suggested that phosphorylation of the inhibitor-2 subunit on tyrosine residues was responsible for the activation, preincubation of the pp60v-src preparation at 41 degrees C resulted in a rapid loss of its protein kinase activities towards both casein and inhibitor-2 while its ability to activate the protein phosphatase complex was relatively insensitive to this treatment. This result demonstrated that pp60v-src was not responsible for activation of the MgATP-dependent protein phosphatase. A protein kinase activity which phosphorylated glycogen synthase on serine residues was detected in the pp60v-src preparation. The protein kinase was active in the presence of inhibitors of phosphorylase kinase, glycogen synthase kinase 5/casein kinase II, and cAMP-dependent protein kinase. It is, therefore, likely that activation of the MgATP-dependent protein phosphatase resulted from the presence of a glycogen synthase kinase 3 like activity in the pp60v-src preparation. Our results illustrate the importance of applying multiple criteria to link the phosphorylation of a protein with an observed change in its activity.
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PMID:Apparent activation of the MgATP-dependent protein phosphatase by pp60v-src. Identification of an activity like that of glycogen synthase kinase 3 in immunoaffinity purified pp60v-src preparations. 301 36

The major secreted isoenzyme of human prostatic acid phosphatase (PAcP) (EC 3.1.3.2), which catalyses p-nitrophenyl phosphate (PNPP) hydrolysis at acid pH values, was found to have phosphotyrosyl protein phosphatase activity since it dephosphorylated three different phosphotyrosine-containing protein substrates. Several lines of evidence are presented to show that the phosphotyrosyl phosphatase and PAcP are the same enzyme. A highly purified PAcP enzyme preparation which contains a single N-terminal peptide sequence was used to test for the phosphotyrosyl phosphatase activity. Both activities comigrated during gel filtration by high performance liquid chromatography. Phosphotyrosyl phosphatase activity and PNPP acid phosphatase activity exhibited similar sensitivities to different effectors. Both phosphatase activities showed the same thermal stability. Specific anti-PAcP antibody reacted to the same extent with both phosphatase activities. PNPP acid phosphatase activity was competitively inhibited by the phosphotyrosyl phosphatase substrate. To characterize further the phosphotyrosyl phosphatase activity, the Km values using different phosphoprotein substrates were determined. The apparent Km values for phosphorylated angiotensin II, anti-pp60src immunoglobulin G and casein were in the nM range for phosphotyrosine residues, which was about 50-fold lower than the Km for phosphoserine residues in casein.
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PMID:Human prostatic acid phosphatase has phosphotyrosyl protein phosphatase activity. 301 2

The substrate specificity of different forms of polycation-stimulated (PCSH, PCSL, and PCSC) phosphorylase phosphatases and of the catalytic subunit of the MgATP-dependent protein phosphatase from rabbit skeletal muscle was investigated. This was done, with phosphorylase a as the reference substrate, using the synthetic phosphopeptides patterned after the phosphorylated sites of pyruvate kinase (type L) (Arg2-Ala-Ser(32P)-Val-Ala (S2), and its Thr(32P) substitute (T4)), inhibitor-1 (Arg4-Pro-Thr(32P)-Pro-Ala (T5), Arg2-Pro-Thr(32P)-Pro-Ala (T1), and its Ser(32P) substitute (S1)), and some modified phosphopeptides (Arg2-Ala-Thr(32P)-Pro-Ala (T2) and Arg2-Pro-Thr(32P)-Val-Ala (T3)), all phosphorylated by cyclic AMP-dependent protein kinase. In addition, casein(Thr-32P), phosphorylated by casein kinase-2, was also tested. The PCS phosphatases show a striking preference for the T4 configuration, PCSC being the least efficient. The catalytic subunit of the MgATP-dependent phosphatase was almost completely inactive toward all these substrates. As shown for the PCSH phosphatase, and comparing with T4, the two proline residues flanking the Thr(P) in T1 and T5, just as in inhibitor-1, drastically imparied the dephosphorylation by lowering the Vmax and not by affecting the apparent Km. The C-terminal proline (as in T2) by itself represents a highly unfavorable factor in the dephosphorylation. The critical effect of the sequence X-Thr(P)-Pro or Pro-Thr(P)-Pro (T1, T2, T5, and inhibitor-1) can be overcome by manganese ions. The additional finding that this is not the case with the Pro-Ser(P)-Pro sequence (S1) suggests that the effect of Mn2+ is highly substrate specific. These observations show the considerable importance of the primary structure of the substrate in determining the specificity of the protein phosphatases.
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PMID:Dephosphorylation of phosphoproteins and synthetic phosphopeptides. Study of the specificity of the polycation-stimulated and MgATP-dependent phosphorylase phosphatases. 302 75

A phosphoprotein phosphatase active towards casein, phosphorylase a and mRNP proteins has been detected in the cytosol of cryptobiotic gastrulae of Artemia sp. This phosphatase has a relative molecular mass (Mr) of 225,000 as measured by gel filtration on Sephadex G-200 and has been purified to near homogeneity by ion-exchange chromatography on different DEAE-substituted matrices, affinity chromatography on polylysine-agarose, histone-Sepharose 4B and protamine-agarose, hydrophobic chromatography on phenyl-Sepharose 4B and gel filtration on Sephadex G-200. Sodium dodecyl sulphate gel electrophoresis of the final purification step revealed that the enzyme contains two types of subunits, alpha and beta, with Mr of 40,000 and 75,000, respectively. These values, in conjunction with the native Mr and the molar ratios of the subunits estimated by densitometric analysis of the gel, suggested that the subunit composition of the enzyme is alpha 2 beta 2. When treated with 1.7% (v/v) 2-mercaptoethanol at -20 degrees C or with ethanol, the enzyme released the catalytic alpha subunit of Mr 40,000. The protein phosphatase was activated by basic proteins e.g. protamine (A 0.5 = 1 microM), histone H1 (A 0.5 = 1.6 microM) and polylysine (A 0.5 = 0.2 microM) and inhibited by ATP (I 0.5 = 12 microM), NaF (I 0.5 = 3.1 mM) and pyrophosphate (I 0.5 = 0.6 mM). The enzyme is a polycation-stimulated protein phosphatase. Purified mRNP proteins, phosphorylated by the mRNP-associated casein kinase type II, are among the substrates used by the enzyme. The function of reversible phosphorylation-dephosphorylation of mRNP as a regulatory mechanism in mRNP metabolism is discussed.
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PMID:Purification, subunit structure and properties of a high-molecular-mass protein phosphatase capable of dephosphorylating mRNP of the brine shrimp Artemia sp. 303 Jul 44

The nature of protein phosphatases of the guinea-pig parotid gland was investigated. The protein phosphatases were characterized by (a) the use of five different 32P-labelled substrate proteins (phosphorylase a, histone H2B, casein, and the alpha and beta subunits of phosphorylase kinase), (b) their behaviour during ion-exchange chromatography, (c) their relative molecular mass distribution during gel filtration, (d) their sensitivity towards inhibition by inhibitor 2, (e) their ability to be stimulated by protamine and (f) by their behaviour during freezing and thawing in the presence of 2-mercaptoethanol. The following results were obtained. 1. The 'cytosol' (100,000 X g supernatant) contains protein phosphatases of the types 1, 2A and 2B. 2. On the basis of inhibition with inhibitor 2 (1.2 micrograms/ml) the 'cytosolic' phosphorylase phosphatase activity consists to about 40% of protein phosphatase 1 and to about 60% of protein phosphatase 2A. 3. In the cytosol about 80-90% of the protein phosphatases 1 and 2A exist in an inactive state. 4. A 5-10-fold activation can be achieved by ethanol precipitation, which results in the generation of a mixture of forms of low apparent molecular mass of about 30 kDa. 5. Microsome-associated phosphorylase phosphatase activities can be extracted in a highly active state by detergent (1% Triton X-100) or by 0.8 M NaCl. 6. Activity measurements in the presence of inhibitor 2 (1.2 micrograms/ml) indicate that the microsomal activities consist to about 75% of protein phosphatase 1 and to about 25% of protein phosphatase 2A. Activities corresponding to protein phosphatases 2B and 2C could not be detected. 7. The 'microsomal' protein phosphatase activities exhibit lower apparent molecular masses (70 kDa and 30 kDa) than the 'cytosolic' protein phosphatases (about 260 kDa). 8. After ethanol treatment of the microsomal protein phosphatases only activities with apparent molecular masses of about 30 kDa can be detected. These share several similarities with the ethanol-treated cytosolic protein phosphatases. 9. Both cytosolic and microsomal protein phosphatases display activity towards histone H2B and casein.
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PMID:Protein phosphatases of the guinea-pig parotid gland. 304 Apr 7

Highly purified repressible acid phosphatase from Saccharomyces cerevisiae very efficiently dephosphorylates 32P-histones and the phosphopeptides Arg-Arg-Ala-Ser-(32P)-Val-Ala and Arg-Arg-Leu-Ser (32P)-Leu-Arg previously phosphorylated by either cAMP-dependent protein kinase or protein kinase-C. The Km values (0.03-1 microM) are very favourable if compared with those calculated for free phosphoaminoacids and p-nitrophenylphosphate which are three to six orders of magnitude higher. While also the phosphopeptide Asp-Ala-Gly-Tyr(32P)-Ala-Arg3-Gly is readily dephosphorylated, other phosphopeptides and phosphoproteins including phosphorylase kinase, phosvitin and casein phosphorylated by both casein kinase 1 and 2 are not appreciably affected by acid phosphatase. It is suggested that yeast repressible acid phosphatase may act in vivo as a phosphoprotein phosphatase.
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PMID:Repressible acid phosphatase from yeast efficiently dephosphorylates in vitro some phosphorylated proteins and peptides. 389 26

The ATP-Mg-dependent phosphoprotein phosphatase is believed to consist of a catalytic subunit and a regulatory component identified as phosphatase inhibitor-2. It was found in this study that isolated inhibitor-2 was phosphorylated in serine residues by casein kinase II to at least 3 mol of phosphate per mol of inhibitor-2 while another protein kinase, F A/GSK-3, introduced no more than 0.3 mol of phosphate per mol exclusively in threonine residues. Analysis of tryptic digests by high performance liquid chromatography indicated that casein kinase II action resulted in two major (peaks 1 and 2) and two minor phosphopeptides whereas F A/GSK-3 action generated only peak 2. Combined action of the two protein kinases introduced an additional 0.4-0.6 mol of phosphate per mol over that predicted for simple additive behavior. This synergistic phosphorylation was associated with increased phosphate in peak 2 and correlated with unchanged phosphoserine but increased phosphothreonine, to a level approaching 1 mol/mol. ATP-Mg-dependent protein phosphatase was either reconstituted from purified inhibitor-2 and low molecular weight type 1 phosphatase or isolated as an inactive complex (Fc). Both phosphatase complexes were activated by F A/GSK-3 which caused a transient phosphorylation of the inhibitor-2 component. Casein kinase II alone phosphorylated the inhibitor-2 in both phosphatase complexes without affecting the enzyme activity. Exposure to the combination of F A/GSK-3 and casein kinase II resulted in a synergistic phosphorylation. Furthermore, the combined action of the two protein kinases caused a synergistic activation of the phosphatase at submaximal F A/GSK-3 levels. The results suggest that interactions between phosphorylation sites may play a role in the activation of the ATP-Mg-dependent phosphatase, in particular that phosphorylation by casein kinase II at serine can potentiate the phosphorylation of threonine by F A/GSK-3 with subsequent influence on phosphatase activation.
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PMID:Synergistic phosphorylation and activation of ATP-Mg-dependent phosphoprotein phosphatase by F A/GSK-3 and casein kinase II (PC0.7). 609 Apr 57


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