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)

Calcineurin, a calmodulin-binding protein from brain, has been shown to possess a metal ion-dependent and calmodulin-stimulated phosphatase activity towards phosphorylase kinase and inhibitor-1 (Stewart, A. A., Ingebritsen, T. S., Manalan, A., Klee, C. B., and Cohen, P. (1982) FEBS Lett. 137, 80-84). In this report, we show that calcineurin can also dephosphorylate p-nitrophenyl phosphate and free phosphotyrosine. However, calcineurin does not show significant activity towards phosphothreonine, phosphoserine, or several other low molecular weight phosphocompounds tested. As we have found with phosphorylase kinase and phosphocasein, the dephosphorylation of p-nitrophenyl phosphate and free phosphotyrosine is stimulated by calmodulin and is metal ion-dependent with the order of efficiency being Mn2+ much greater than Co2+ greater than Ca2+. The dephosphorylation of these substrates appears to be an intrinsic property of calcineurin and is not due to contamination by alkaline phosphatases since the pH optimum for calcineurin activity occurs at a neutral rather than an alkaline pH. The dephosphorylation of p-nitrophenyl phosphate provides an easy, rapid, and accurate method for the quantification of calcineurin activity as well as permitting insight into reaction kinetics. The dephosphorylation of free phosphotyrosine by calcineurin suggests that this compound may be a physiological substrate of calcineurin.
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PMID:Calmodulin-stimulated dephosphorylation of p-nitrophenyl phosphate and free phosphotyrosine by calcineurin. 619 Aug 10

Preincubation of two homogeneous rabbit liver phosphoprotein phosphatases (phosphophoprotein phosphohydrolases, EC 3.1.3.16) (Khandelwal, R.L., Vandenheede, J.R. and Krebs, E.G. (1976) J. Biol. Chem. 251, 4850-4858) with ATP, ADP and PPi caused a time- and concentration-dependent inactivation of the enzyme activity. A 50% inactivation of phosphoprotein phosphatase I required relatively low concentration of inactivating metabolite and less preincubation time as compared to the inactivation of phosphoprotein phosphatase II. AMP, adenosine, adenine, Pi, EDTA, EGTA, 1,10-phenanthroline and diethyl dithiocarbamate were without effect on both enzymes. Pretreatment of both enzymes by metal-chelating agents followed by PPi did not augment the effect observed with PPi alone. Both inactivated enzymes could be reactivated by cobalt or manganese in the presence of dithiothreitol. Although the extent of reactivation by these two metal ions was almost similar, cobalt required a ten times lower concentration than manganese for this process. No difference in inactivation or reactivation of both enzymes was observed with different substrates, phosphorylase a, histone or casein, employed in the assay. Pi and PPi added during the assay inhibited activities of both phosphatases with phosphorylase a and casein substrates. With histone as substrate, PPi slightly inhibited enzyme activities at lower concentrations (0.01-0.25 mM) but activated at higher concentrations. Pi activated both enzymes with this substrate; maximal activation being observed at a concentration of 5 mM.
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PMID:Studies on in activation and reactivation of homogeneous rabbit liver phosphoprotein phosphatases by inorganic pyorphosphate and divalent cations. 624 57

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.
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PMID:Phosphoprotein phosphatase associated with rat liver plasma membrane. Properties of phosphorylase phosphatase and phosphohistone phosphatase. 627 67

The catalytic subunit of phosphoprotein phosphatase (Mr = 35,000) is inactivated by phosphate compounds such as trimetaphosphate, PPi, and ATP. The inactivation of phosphoprotein phosphatase by these phosphate compounds is time- and concentration-dependent, is not reversed by dilution or gel filtration and is protected by Pi. A dissociation constant for the enzyme-trimetaphosphate complex and a rate constant for the reaction were calculated to be 4.6 x 10(-4) M and 0.29 min-1, respectively. The inactivation of phosphatase by PPi and ATP shows more complex kinetics than that by trimetaphosphate. The addition of EDTA to PPi and ATP exhibits more potent inactivation, even though EDTA alone does not inactivate phosphatase. This phosphoprotein phosphatase is not labeled by [gamma-32P]ATP. The inactivation of phosphatase by PPi or ATP can only be reversed by Mn2+ or Co2+, among all other metals or cationic compounds tried. The reactivation also requires sulfhydryl compounds. The effectiveness of sulfhydryl compounds follows the order: dithioerythritol greater than mercaptoethanol greater than cysteine. Glutathione was without effect. Metal analysis of the catalytic subunit did not reveal any significant amounts of Ca, Cd, Co, Cu, Fe, Mg, Mn, Ni, Sn, or Zn. Phosphoprotein phosphatase activity from zinc-deficient rat livers also eliminated the possibility of this phosphatase being a zinc metalloenzyme. Inactivation does not seem to be due to a loss of a critical metal ion. Other mechanisms for inactivation are presented.
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PMID:Inactivation and reactivation of phosphoprotein phosphatase. 627 82

Calcineurin purified from bovine brain is shown to possess phosphotyrosyl -protein phosphatase activity towards proteins phosphorylated by the epidermal growth factor receptor/kinase. The phosphatase activity is augmented by Ca2+/calmodulin or divalent cation (Ni2+ greater than Mn2+ greater than Mg2+ greater than Co2+). In the simultaneous presence of all three effectors, the enzymatic activity is synergistically increased. Ca2+/calmodulin activates the Mg2+-supported activity by decreasing the Km value for phosphotyrosyl -casein from 2.2 to 0.6 microM, and increasing the Vmax from 0.4 to 4.6 nmol/min/mg. These results represent the first demonstration that calcineurin can dephosphorylate phosphotyrosyl -proteins and suggest a novel mechanism of activation of this enzyme.
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PMID:Characterization of phosphotyrosyl-protein phosphatase activity associated with calcineurin. 632 93

1. Whole-cell patch-clamp technique was used to study the beta-adrenergic and cholinergic regulation of the inwardly rectifying K+ conductance (gK1) in isolated guinea-pig ventricular myocytes. 2. In Cl(-)-free solutions or in the presence of 9-anthracenecarboxylic acid or Co2+, bath-applied isoprenaline (Iso) partially inhibited the steady-state whole-cell conductance (gss) calculated from the steady-state current (Iss)-voltage (Iss-V) curve at membrane voltages (Vm) negative to the equilibrium potential for potassium (EK). Iss was also inhibited at Vm positive to EK when the extracellular [K+] was 20 mM. The Iso-sensitive component of gss exhibited the characteristics of the inwardly rectifying K+ conductance (gK1). 3. The Iso-induced inhibition of gK1 was reversible, concentration dependent, blocked by propranolol, mimicked by both forskolin and dibutyryl cAMP, and prevented by including a cAMP-dependent protein kinase (PKA) inhibitor in the pipette solution. These findings suggest that PKA mediates the Iso-induced inhibition of gK1. 4. The apparent dissociation constant (KD) for the concentration dependence of Iso-induced inhibition was 0.035 microM and the Hill coefficient was approximately 1.0. A maximal Iso concentration (1 microM) inhibited gK1 by 40 +/- 4.1% (mean +/- S.E.M.; n = 13). 5. Bath application of acetylcholine (ACh, 0.1 microM or more) antagonized the Iso-induced (1 microM) inhibition of gK1; [ACh] > 1.0 microM antagonized 88 +/- 2.1% (n = 10) of the inhibition. ACh increased the KD for Iso to inhibit Iso-sensitive gK1 and also reduced the maximal Iso-induced inhibition. 6. ACh-induced antagonism could be abolished by pre-incubating myocytes with pertussis toxin (PTX), suggesting that a muscarinic receptor-coupled, PTX-sensitive G protein, Gi, is involved. 7. ACh (10 microM) also antagonized approximately 70% of the dibutyryl cyclic AMP (1 mM)-induced inhibition of gK1 (n = 3), suggesting that the ACh-induced antagonism involves more than simply inhibiting the Iso-mediated activation of adenylyl cyclase via the activated Gi. 8. Intracellularly applied okadaic acid (OkA, 1 microM) did not alter gK1 (control = 134 +/- 5.1 nS vs. OkA = 136 +/- 6.1 nS), but the Iso-induced decrease in gK1 was less (P < 0.001) with OkA present (42.1 +/- 2.4 nS, n = 5) than when absent (54.0 +/- 2.2 nS, n = 10). However, ACh (10 microM) failed to antagonize Iso-induced inhibition with OkA present, suggesting involvement of a protein phosphatase.
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PMID:beta-adrenergic and cholinergic modulation of the inwardly rectifying K+ current in guinea-pig ventricular myocytes. 747 26

Highly purified bovine heart protein phosphatase 2A catalytic subunit lost virtually all of its activity during storage at -70 degrees. When the enzyme was preincubated with Co2+, over 35% of the original activity was restored. Freshly prepared protein phosphatase 2A purified from bovine heart was stimulated at least 3 to 4-fold by pretreatment with Co2+ or Mn2+. Activation by Co2+ appeared to be irreversible whereas activation by Mn2+ was partially reversed after the cation was chelated with excess EDTA/EGTA. The sensitivity of Co2(+)-stimulated protein phosphatase 2A to okadaic acid or inhibitor-2 was similar to that of spontaneously active protein phosphatase 2A. The enzyme was converted to a latent form by treatment with phosphate or pyrophosphate. The latent form was completely reactivated by preincubation with Co2+. These results demonstrate that protein phosphatase 2A, like phosphatase 1, can exist in a metal ion-dependent form and may represent a new mechanism for the regulation of protein phosphatase 2A activity.
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PMID:A metal-dependent form of protein phosphatase 2A. 788 40

The catalytic subunit of the major protein phosphatase associated with bovine cardiac myofibrils was purified to homogeneity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the enzyme revealed only one band with an apparent molecular weight of 37,000. On gel filtration chromatography, the phosphatase activity and the protein co-eluted as a single peak with an apparent molecular weight of 37,000. The purified enzyme was identified as the catalytic subunit of protein phosphatase 1, as determined by sensitivity to inhibitor 1, inhibitor 2, okadaic acid and by specific immunostaining. Evidence obtained with specific antipeptide antibodies demonstrated that this myofibril protein phosphatase was predominantly the alpha isoform of protein phosphatase 1. The purified catalytic subunit was completely inactive. It was activated by pretreatment with Co2+/trypsin in the presence of high ionic strength. Treatment with trypsin alone did not activate the latent enzyme. The enzyme was also activated by Co2+ or Mn2+ alone but not by Ca2+, Mg2+, Ni2+, Cu2+ or Zn2+. Activation of the enzyme was not reversed by removal of Co2+, but Mn(2+)-activated phosphatase activity was partially reversed when Mn2+ was removed. The catalytic subunit could form a 1:1 complex with inhibitor 2 in vitro. The resulting holoenzyme was also activated by pretreatment with Co2+. Since phosphatase 1 alpha is the major phosphatase associated with cardiac myofibril, it is suggested that it is responsible for the dephosphorylation of myosin and other myofibril phosphoproteins.
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PMID:A latent form of protein phosphatase 1 alpha associated with bovine heart myofibrils. 808 38

We have observed that soluble extracts from the extreme acidothermophilic archaebacterium Sulfolobus solfataricus contained protein phosphatase activity that was greatly stimulated by the divalent metal ions Mn2+, Mg2+, Ni2+, or Co2+. This activity apparently arose from a single enzyme since (a) stimulation by these divalent metal ions was not additive and (b) protein phosphatase activity eluted as a single peak from both a DE52 ion-exchange column and a Sephadex G-100 gel filtration column. Its apparent molecular mass was approximately 28,000 daltons. The enzyme dephosphorylated a variety of phosphoserine-containing substrates including casein, histone H2a, phosphorylase kinase, or glycogen phosphorylase. The enzyme would not dephosphorylate either histone H1 or a number of phosphotyrosine-containing compounds. It removed only half the phosphate bound to histone H2b, which is phosphorylated at two sites by the cAMP-dependent protein kinase. Protein phosphatase activity was inhibited by EDTA, Cu2+, Zn2+, NaF, inorganic phosphate, or pyrophosphate; but was unaffected by other potential activators and inhibitors such as microcystin, okadaic acid, vanadate, polyamines, or sulfhydryl modifying reagents. This enzyme represents the first protein phosphatase to be identified in any member of the third and oldest phylogenetic kingdom in nature, the archaebacteria.
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PMID:Identification of a serine/threonine-specific protein phosphatase from the archaebacterium Sulfolobus solfataricus. 838 14

The recombinant catalytic subunit of protein phosphatase 1 is produced as an inactive enzyme which can be activated by Mn2+ (Zhang, Z., Bai, G., Deans-Zirattu, S., Browner, M. F., and Lee, E. Y. C. (1992) J. Biol. Chem. 267, 1484-1490). In this report, we have investigated the effects of divalent cations on the activity of recombinant catalytic subunit of protein phosphatase 1. Latent phosphatase 1 can be activated by Co2+ or Mn2+, whereas other metal ions tested including Fe2+, Zn2+, Mg2+, Ca2+, Cu2+, or Ni2+ were not effective or were only weakly effective in activating the enzyme. The Mn(2+)-stimulated activity was susceptible to inactivation by EDTA; however, the Co(2+)-activated phosphatase was stable after dilution and chelation of the Co2+ with excess EDTA. After stable activation of phosphatase 1 using 57Co2+, a stoichiometric amount of 57Co2+ was shown to be tightly bound to phosphatase 1. These findings demonstrate for the first time the generation of a stable metalloenzyme form of phosphatase 1. Fe2+ reversibly deactivated the Co(2+)-stimulated activity, but did not displace the bound Co2+. Interestingly, treatment of the enzyme with a combination of Fe2+ and Zn2+ (but not the individual metal ions) significantly activated phosphatase 1. These results suggest that at least two metal binding sites exist on the enzyme and that protein phosphatase 1 may be an iron/zinc metalloprotein in vivo.
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PMID:Activation of protein phosphatase 1. Formation of a metalloenzyme. 857 23


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