Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ca2+ accumulation at pH 6.8 by isolated rabbit heart microsomes derived chiefly from sarcoplasmic reticulum was investigated by a quench-flow technique. The reaction was terminated at preset times by addition to the reaction mixture of an equal volume of 10 to 50 mM ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid buffered at pH 6.0. The initial velocity of Ca2+ accumulation by microsomal preparations exhibiting a steady state Ca2+ accumulation of 25.6 nmol Ca2+/mg increased from 3.67 to 33.4 nmol Ca2+/mg - s as the free Ca2+ concentration was raised from 0.2 to 18.9 muM. Preincubation of the cardiac microsomes with a partly purified soluble cardiac cyclic AMP-dependent protein kinase, MgATP, and cyclic AMP lead to a significant increase in the initial Ca2+ accumulation rate. The amounts of Ca2+ that were found to accumulate in the first 200 ms of the reaction are comparable to the quantities of the ion that according to literature data need to be removed from the myofilaments and the myoplasm for induction of relaxation of the myocardial fibers.
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PMID:A quench-flow kinetic investigation of calcium ion accumulation by isolated cardiac sarcoplasmic reticulum. Dependence of initial velocity on free calcium ion concentration and influence of preincubation with a protein kinase, MgATP, and cyclic AMP. 18 17

This research explored the possibility that cyclic nucleotides are part of the excitation-secretion sequence in mammalian motor nerve terminals. A series of reagents known to react with the enzymes that synthesize and degrade cyclic nucleotides or that are effectors of cyclic nucleotide actions were administered to in vivo cat soleus nerve-muscle preparations. The reagents were administered by rapid close intra-arterial injection while electrical activity in single motor axons and contractile activity of the muscle were monitored. NaF, an activator of adenylate cyclase, evoked bursts of action potentials in unstimulated axons and caused stimulus-bound repetitive activity in stimulated axons. It evoked vigorous asynchronous activity in the muscle and potentiated the force of muscle contraction. These effects are identical with those of cyclic N6-2'-O-dibutyryl adenosine 3':5'-monophosphate (dibutyryl cAMP). Prostaglandin E1 produced similar effects. Dithiobisnitrobenzoic acid and alloxan, inhibitors of adenylate cyclase, impaired neuromuscular transmission and prevented the effects of NaF, but they did not change the responses to dibutyryl cAMP. Theophylline, an inhibitor of phosphodiesterase, caused axons to respond repetitively to stimulation, but this activity had a different pattern from that produced by dibutyryl cAMP or NaF. Pretreatment with theophylline enhanced the responses to dibutyryl cAMP and NaF. Imidazole, an activator of phosphodiesterase, impaired neuromuscular transmission and prevented the effects of dibutyryl cAMP and NaF. Adenosine, an inhibitor of protein kinase, or verapamil, which inhibits calcium flux, impaired neuromuscular transmission and prevented the responses to dibutyryl cAMP, NaF and theophylline. These results are compatible with the hypothesis that cAMP is involved in the regulation of calcium flux and transmitter secretion in mammalian motor nerve terminals.
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PMID:A role of cyclic nucleotides in neuromuscular transmission. 18 85

The liberation of arachindonate in the thyroid occurs at the expense of two distinct pools of precursors. (1) the phosphatidylinositol through a process Ca2+-dependent and cyclic AMP-independent; and (2) the triglycerides by a cyclic AMP-dependent lipase, in which the involvement of cyclic AMP-dependent protein kinase has not yet been determined. The "PI pool" or "paracyclic AMP pool" is mobilized very rapidly by large doses of TSH but its physiological significance can be discussed. The "triglyceride pool" or "post-cyclic AMP pool" is mobilized more slowly by small doses of TSH and seems not to be implicated in the acute TSH stimulation of adenylate cyclase. The "post-cyclic AMP pool" of prostaglandins would be very important as third messenger or as "long-acting TSH hormone". Some recent works of Boeynaems and Van Sande (16) and Madaoui et al. (17) on the thyroid support this hypothesis, as aspirin or indomethacin inhibits DBc-AMP stimulation of glucose oxydation, iodine organification, or thyroid hormone secretion. On the other hand, in the absence of prostaglandin synthesis, TSH still stimulates the adenylate cyclase, which means that prostaglandins are not obligatory intermediates of hormonal action on cyclic AMP production. In conclusion, these results show a TSH action in the thyroid on the release of fatty acids, precursors of PG's, from their lipidic stores. Nevertheless, a second control step is not excluded in conversion of cyclic endoperoxide to PGE or PGFalpha.
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PMID:Stimulation by TSH of prostaglandin synthesis in pig thyroid. 18 42

Cardiac myofibrils were purified from canine myocardium, and the regulatory proteins (troponin + tropomyosin) were extracted and shown to contain endogenous cyclic AMP-dependent protein kinase activity. Other cyclic nucleotide stimulated the protein kinase activity but only at higher concentrations. The enzyme was able to catalyze phosphorylation of conventional substrates such as histones and casein as well as a component of the regulatory protein fraction with a molecular weight of 28,000 daltons. Endogenous phosphorylation required the presence of Mg2+ and was inhibited by Ca2+. A protein kinase inhibitor obtained from skeletal muscle inhibited the cyclicAMP-dependent phosphorylation. Escherichia coli alkaline phosphatase dephosphorylated the endogenous substrates. The level of phosphorylation found is severalfold higher than we have previously reported. A protein kinase, with its close association with the regulatory proteins, seems to be well suited to transmitting the message from the cyclic AMP to the regulatory proteins, a phenomenon that may influence the cardiac contractility via the troponin phosphorylation. The inhibitory effect of troponin on actomyosin might be changed by its state of phosphorylation.
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PMID:Phosphorylation of cardiac regulatory proteins by cyclic AMP-dependent protein kinase. 18 66

We have studied the mode of action of three hormones (angiotensin, vasopressin and phenylephrine, an alpha-adrenergic agent) which promote liver glycogenolysis in a cyclic AMP-independent way, in comparison with that of glucagon, which is known to act essentially via cyclic AMP. The following observations were made using isolated rat hepatocytes: (a) In the normal Krebs-Henseleit bicarbonate medium, the hormones activated glycogen phosphorylase (EC 2.4.1.1) to about the same degree. In contrast to glucagon, the cyclic AMP-independent hormones did not activate either protein kinase (EC 2.7.1.37) or phosphorylase b kinase (EC 2.7.1.38). (b) The absence of Ca2+ from the incubation medium prevented the activation of glycogen phosphorylase by the cyclic AMP-independent agents and slowed down that induced by glucagon. (c) The ionophore A 23187 produced the same degree of activation of glycogen phosphorylase, provided that Ca2+ was present in the incubation medium. (d) Glucagon, cyclic AMP and three cyclic AMP-dependent hormones caused an enhanced uptake of 45Ca; it was verified that concentrations of angiotensin and of vasopressin known to occur in haemorrhagic conditions were able to produce phosphorylase activation and stimulate 45Ca uptake. (e) Appropriate antagonists (i.e. phentolamine against phenylephrine and an angiotensin analogue against angiotensin) prevented both the enhanced 45Ca uptake and the phosphorylase activation. We interpret our data in favour of a role of calcium (1) as the second messenger in liver for the three cyclic AMP-independent glycogenolytic hormones and (2) as an additional messenger for glucagon which, via cyclic AMP, will make calcium available to the cytoplasm either from extracellular or from intracellular pools. The target enzyme for Ca2+ is most probably phosphorylase b kinase.
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PMID:On the role of calcium as second messenger in liver for the hormonally induced activation of glycogen phosphorylase. 18 44

A procedure for the purification of cholesterol ester hydrolase from bovine adrenal cortical 105000 x g supernatant is described. Preincubation of a crude enzyme extract with [gamma-32P]ATP followed by purification resulted in the isolation of a phosphorylated preparation of cholesterol ester hydrolase. The phosphorylated cholesterol ester hydrolase appeared to be composed of 4 subunits, each having a molecular weight of 41000 +/- 280, only one of which may be phosphorylated. Preincubation of the crude enzyme preparation with [alpha-32P]ATP followed by purification did not produce a phosphorylated preparation of cholesterol ester hydrolase. Cyclic-AMP-dependent protein kinase, cyclic AMP, ATP and magnesium ions were required for activation of purified cholesterol ester hydrolase in vitro and the time course of activation closely paralleled the time course of phosphorylation of the enzyme. The addition of ATP, cyclic AMP and magnesium ions to the bovine adrenal cortical 105000 x g supernatant produced a 2.5-fold stimulation in cholesterol ester hydrolase activity. This stimulation was abolished if protein kinase inhibitor was added prior to the addition of ATP cyclic AMP and magensium ions. The addition of magnesium ions or calcium ions to a crude preparation of cholesterol ester hydrolase was found to inhibit activity; however the same additions made to a purified preparation of cholesterol ester hydrolase were not inhibitory. The decrease in cholesterol ester hydrolase activity on incubation with magnesium ion was accompanied by a loss of 32P radioactivity from the protein. Preincubation of a crude preparation of cholesterol ester hydrolase with alkaline phosphatase resulted in a deactivation of cholesterol ester hydrolase. It is suggested that bovine adrenal cortex cholesterol ester hydrolase is activated by a phosphorylation catalysed by a cyclic-AMP-dependent protein kinase. Deactivation of cholesterol ester hydrolase is accomplished by dephosphorylation catalysed by a phosphoprotein phosphatase, dependent on magnesium or calcium ions.
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PMID:Purification and control of bovine adrenal cortical cholesterol ester hydrolase and evidence for the activation of the enzyme by a phosphorylation. 18 99

The events involved in platelet shape change, aggregation, the release reaction and contraction are thought to be mediated by the availability of Ca2+. Increased cytoplasmic calcium, released from intracellular stores, triggers platelet activity, and increased concentration of adenosine 3',5'-cyclic monophosphate (cyclic AMP) inhibits platelet alterations. We have studied the hypothesis that cyclic AMP may regulate the level of platelet cytoplasmic calcium by stimulating calcium removal by a membrane system. Such a hypothesis would be consistent with the reversibility of most manifestations of platelet activation. Human platelets were sonicated and unlysed platelets, mitochondria and granules were removed by centrifugation at 19 000 X g. Electron microscopy shows that the sediment, after centrifugation of the supernatant at 40 000 X g consists to a large extent of membrane vesicles. Such preparations actively concentrate calcium, as measured by the uptake of 45Ca, and also have the maximal calcium-stimulated ATPase activity. Optimal calcium uptake requires ATP and oxalate, and release of calcium from loaded vesicles was stimulated by the calcium ionophore A23187 and inhibited by LaCl3. These data indicate that calcium was being actively concentrated within membrane vesicles. After washing of such preparations in the absence of ATP, their capacity to take up Ca2+ is reduced to an initial value of 2.8 nmol/mg protein per min. In the presence of 2 - 10(6) M cyclic AMP to which was added a protein kinase preparation from human platelets, up to a 3-fold increase of this rate of uptake was observed. These results suggest that in platelets, as in muscle, cyclic AMP is a regulatory factor in the control of cytoplasmic calcium. Although the cyclic nucleotide may have still other functions, it appears likely that the well-known inhibition of many platelet activities by high intracellular cyclic AMP concentrations is directly linked to the stimulation of the removal of Ca2+ from the cytoplasm.
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PMID:Stimulation of calcium uptake in platelet membrane vesicles by adenosine 3',5'-cyclic monophosphate and protein kinase. 19 95

Ca2+ uptake and binding and Ca2+-ATPase activity of cardiac sarcoplasmic reticulum (SR) from spontaneously hypertensive rats (SHR) were compared to that obtained from normotensive Wistar-Kyoto (WKY) rats. Ca2+ uptake (172 +/- 3.7 nmol/mg of protein per min in WKY vs. 112 +/- 2.6 in the SHR, P less than 0.001) and binding (154 +/- 3.0 nmol/mg per min in WKY vs. 101 +/- 1.8 in the SHR, P less than 0.01) were decreased in the SHR. Ca2+-ATPase activity, however, was significantly higher in the SHR (118 +/- 3.1 nmol of P per mg of protein per min vs. 86 +/- 1.1 in the WKY, P less than 0.001), suggesting "uncoupling" of the ATPase to calcium transport. Cyclic AMP-dependent phosphorylation of SR was significantly decreased in SHR (0.71 +/- 0.05 vs 0.32 +/- 0.07 nmol of P/mg of protein per 10 min, P less than 0.001) and there was an excellent correlation between cyclic AMP-induced phosphorylation of SR and Ca2+ uptake (r = 0.81). Differences in both cyclic AMP-dependent phosphorylation and Ca2+ uptake between the two groups were evident at 10 weeks and increased progressively to 22 weeks of age. Differences in endogenous cyclic AMP-dependent protein kinase activity may partly explain the decreased Ca2+ transport in SHR.
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PMID:Defective calcium transport by cardiac sarcoplasmic reticulum in spontaneously hypertensive rats. 19 87

A thermostable inhibition of ATP-protein phosphotransferase (EC 2.7.1.37) (protein kinase) which is present in crude tissue extracts has been resolved by gel chromatography (Sephadex G-100) into two molecular forms. These two forms will be referred to as type I and type II inhibitor. The type I inhibitor (Mr approximately or equal to 24,000) is specific for cAMP-dependent protein kinase and corresponds to the inhibitor described earlier (Walsh, D. A., Ashby, C. D., Gonzalez, C., Calkins, D., Fisher, E. H., and Krebs, E. G. (1971) J. Biol. Chem. 246, 1977-1985). The type II inhibitor (Mr approximately or equal to 15,000) competes for the enzyme with various substrate proteins (histone, alpha-casein, and Leu-Arg-Arg-Ala-Ser-Leu-Gly (kemptide). The type II inhibitor blocks protein phosphorylation catalyzed by several types of protein kinases (cAMP- and cGMP-dependent or cyclic nucleotide-independent protein kinases). The type II inhibitor from rat brain has been purified 1500-fold; this protein is thermostable, has acidic characteristics, and does not require Ca2+ ions for its activity. Different ratios and concentrations of type I and type II inhibitors of protein kinase are found in rat skeletal muscle, pancreas, cerebellum and corpus striatum, and in lobster tail muscle.
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PMID:Endogenous protein kinase inhibitors. Purification, characterization, and distribution in different tissues. 19 48

The role of cyclic 3',5'-AMP in modulating sarcoplasmic reticulum from fast skeletal muscle was studied. The rate of Ca2+ uptake was stimulated in the presence of protein kinase plus 1 micron cyclic AMP. The stimulation was absent when denatured protein kinase was used. When an adenylate cyclase inhibitor was added, the uptake rates fell to 55% of control. This decrease in rate was partially overcome by 1 micron cyclic AMP. A modulating role for cyclic AMP in fast skeletal muscle is proposed.
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PMID:Cyclic AMP modulation of calcium accumulation by sarcoplasmic reticulum from fast skeletal muscle. 19 7


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