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:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The formation of translational inhibitor (active eIF-2 kinase) from proinhibitor (inactive eIF-2 kinase) in reticulocyte lysates, known to be controlled by hemin, can, as we recently reported, be induced by 3':5'-cyclic AMP(cAMP)-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) or its catalytic subunit. We find that in crude preparations from rabbit reticulocyte lysates, hemin inhibits the conversion of proinhibitor to inhibitor catalyzed by endogenous cAMP-dependent protein kinase upon addition of cAMP, but not that caused by the addition of free protein kinase catalytic subunit. Hemin prevents the binding of cAMP to the regulatory subunit of cAMP-dependent protein kinase and blocks the cAMP-induced dissociation of regulatory and catalytic subunits of the enzyme whereby the enzyme is inactivated. The mechanism by which hemin prevents the formation of the inhibitor and maintains protein synthesis in reticulocyte lysates is thus explained.
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PMID:Mechanism of translational control by hemin in reticulocyte lysates. 19 82

The cAMP-dependent protein kinase from various tissues was more thermally sensitive when activated by cAMP than the non-activated enzyme. For example, when the activity ratio (the activity of protein kinase assayed -cAMP/+cAMP) was 0.40, 80% and 76% of total hepatic cAMP dependent protein kinase activity was recoverable after incubations at 45 degrees C for 15 and 30 minutes, respectively. However, when the activity ratio was elevated to about 0.80 - 0.90 by increasing cAMP levels in vivo or adding exogenous cAMP to soluble liver extracts, the total protein kinase activity recoverable after incubations at 45 degrees C for 15 minutes was 34-44% and 19-22%, respectively. This observation was used to estimate the degree of activation of the enzyme in vivo and in vitro, since the loss of enzyme activity at 45 degrees C was directly related to the degree of activation of the enzyme in tissue extracts. The regulatory-catalytic form of cAMP-dependent protein kinase was thermally resistant at 45 degrees C unless activated by incubation with exogenous cAMP, histones or NaCl, while the catalytic form of the enzyme was highly thermally sensitive at this same temperature. These data describe a new property of the cAMP-dependent protein kinase and suggest an alternative method which measure the degree of activation of the enzyme.
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PMID:Differences in thermal sensitivities of the regulatory-catalytic and catalytic forms of cyclic AMP-dependent protein kinases from various tissues. 19 30

The effect of prostaglandin E1(PGE1) and epinephrine on glycogen metabolism has been investigated in the perfused rat heart. Both agents produced increases in cAMP and the cAMP-dependent protein kinase activity ratio. When dosages were adjusted to give equal increases in the protein kinase activity ratio from a basal value of 0.15 to as high as 0.40, only epinephrine caused a significant increase in phosphorylase activity. When used together, PGE1 did not effect the ability of epinephrine to increase phosphorylase activity.
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PMID:Activation of cAMP-dependent protein kinase without a corresponding increase in phosphorylase activity. 19 22

The high-affinity binding site for ATP of the holoenzyme of cAMP-dependent protein kinase (type I) from rabbit skeletal muscle has been investigated. Binding affinity of a series of ATP derivatives substituted at different sites in the molecule was determined by competition with tritiated ATP. The results were compared with data available from cAMP derivatives with the same substituents, in order to analyse the electronic and steric features of these two sites on the protein kinase. The comparison revealed significant differences of the effect of substituents towards the two sites. In particular the N6-derivatives of ATP and substituents affecting the gamma-phosphate indicate that the high-affinity ATP site of the protein kinase has similar properties as those found for phosphotransferase sites. The present results are consistent with the supposition that the high-affinity site for ATP on the holoenzyme is congruent with the phosphotransferase site of the catalytic subunit. Upon combination of catalytic and regulatory subunits this site would be transformed into a high-affinity site for ATP with simultaneous blocking of the phosphotransferase activity.
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PMID:Mechanism of activation of the protein kinase I from rabbit skeletal muscle. The high-affinity ATP site of the holoenzyme. 20 Apr 26

Synthetic polypeptides were employed as substrates in kinetic analyses of the reaction mechanism for the catalytic subunit of a cyclic AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) from calf thymus. This enzyme preparation was shown to catalyze the transfer of phosphate from ATP to histone H1 from calf thymus, as well as to two synthetic polypeptides, Arg-Lys-Ala-Ser-Gly-Pro (H1-6) and Arg-Arg-Lys-Ala-Ser-Gly-Pro (H1-7), corresponding to the amino acid sequence about serine-38 in calf H1. A related, basic heptapeptide corresponding to a sequence from pig liver pyruvate kinase, Leu-Arg-Arg-Ala-Ser-Leu-Gly (K), was also a substrate. The stoichiometry of peptide phosphorylation was established in each case as the transfer of 1 mol of phosphate from the gamma position of MgATP to the serine hydroxyl of 1 mol of the peptide. Steady-state, initial-velocity, kinetic parameters were determined for each substrate, using various concentrations of ATP. Under the conditions used, all synthetic peptides reacted with greater maximum velocities than whole histone H1. Nevertheless, the K(m) for H1, 54 muM, was lower than the K(m) values of the synthetic substrates. The most efficient substrate was peptide K, which had a V(max) of 50.6 mumol/min per mg of kinase and a K(m) of 63 muM. In the absence of peptide substrate no ATPase activity was detectable at a sensitivity of 0.05% of the rate of peptide phosphorylation, suggesting that ATP is not cleaved to form an unstable phosphoenzyme complex. The data are consistent with a sequential reaction mechanism involving a ternary complex between enzyme, polypeptide substrate, and ATP.
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PMID:Studies on the mechanism of phosphorylation of synthetic polypeptides by a calf thymus cyclic AMP-dependent protein kinase. 20 Sep 11

Homogeneous cGMP-dependent protein kinase catalyzes the rapid incorporation of phosphate, specifically into the inhibitory subunit of purified cardiac troponin with a maximal incorporation of 1 mol of phosphate/mol of troponin. When troponin was incubated in the presence of both cGMP- and cAMP-dependent protein kinases, a maximal incorporation of 1 mol of phosphate/mol of troponin was observed which suggested phosphorylation of the same site by the two kinases. Both cyclic nucleotide-dependent kinases had similar Km values for troponin, but the Vmax value for the phosphorylation reaction catalyzed by cAMP-dependent protein kinase was 12-fold greater than the value obtained for cGMP-dependent protein kinase.
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PMID:Phosphorylation of cardiac troponin by guanosine 3':5'-monophosphate-dependent protein kinase. 20 26

Properties of the ATP-dependent calcium transport system of heart sarcolemma are presented. Calcium accumulation (with oxalate) in sarcolemma was increased due to cAMP-dependent protein kinase and phosphorylase b kinase. Protein kinase increased the Vmax of the sarcolemmal calcium accumulation without any detectable effect on the affinity for Ca2+. Both kinases failed to stimulate calcium binding. Protein kinase catalyzed phosphorylation of membrane proteins of molecular weights of 100,000, 25,000, and 14,000. Phosphorylase b kinase also catalyzed phosphorylation of these proteins. Protein kinase stimulated ATPase activity of sarcolemma. Sarcolemma contained endogenous protein kinase and protein phosphatase activities.
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PMID:Characteristics of heart sarcolemmal calcium transport system and effect of protein kinase on sarcolemmal calcium accumulation. 20 83

Phospholamban (molecular weight = 22,000), which serves as a regulator of Ca transport ATPase (molecular weight = 100,000) of cardiac sarcoplasmic reticulum (SR), becomes resistant to tryptic digestion upon phosphorylation by cAMP-dependent protein kinase (PK). The protective effect of phosphorylation is accompanied by persistence of the PK-induced stimulation of Ca transport. These findings indicate that structural alteration of phospholamban upon phosphorylation is closely associated with changes in the functional properties of cardiac SR. SR from fast-contracting skeletal muscle of rabbit does not contain a 22,000-dalton substrate for cAMP-dependent PK, nor is Ca transport stimulated by exogenous PK. SR preparation isolated from slow-contracting skeletal muscle of rabbit and dog contains phospholamban, and Ca transport was found to be increased by exogenous cAMP-dependent PK. In view of the distribution of phospholamban among different types of muscle, a hypothesis is presented to explain the relaxation-promoting effects of catecholamines in cardiac and slow-contracting skeletal muscle in which phospholamban is found. This may also account for the absence of a similar effect of catecholamines in fast-contracting skeletal muscle, which does not contain a similar substrate for PK.
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PMID:Significance of the membrane protein phospholamban in cyclic AMP-mediated regulation of calcium transport by sarcoplasmic reticulum. 20 84

The heat-stable protein (protein kinase modulator), partially purified from fresh bovine heart, possessed the ability to inhibit and stimulate adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase and guanosine 3':5'-monophosphate (cGMP)-dependent protein kinase activities, respectively. The inhibitory activity of protein kinase modulator on cAMP-dependent protein kinase was abolished almost completely by trypsin treatment, while the ability to stimulate cGMP-dependent protein kinase activity was resistant to trypsin. Fractionation by a linear potassium phosphate gradient on DEAE-cellulose column did not clearly separate both activities. Phosphorylation of cardiac microsomal component, "phospholamban" (molecular weight = 22,000), was inhibited almost completely by the saturating amounts of protein kinase modulator. This inhibition of phospholamban phosphorylation by protein kinase modulator was accompanied by a decreased Ca uptake rate that had been stimulated by cAMP-dependent protein kinase. These findings indicate that protein kinase modulator is functional in controlling the cAMP-dependent protein kinase-catalyzed phosphorylation of phospholamban and the rate of calcium transport, lending further support for the previously proposed mechanism, in which phospholamban is assumed to serve as a regulator of calcium transport in cardiac sarcoplasmic reticulum.
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PMID:Effect of protein kinase modulator on cAMP-dependent protein kinase-catalyzed phosphorylation of phospholamban and stimulation of calcium transport in cardiac sarcoplasmic reticulum. 20 86

Similar time courses were obtained for decreases in the rate of calcium transport by cardiac sarcoplasmic reticulum vesicles previously phosphorylated by cAMP-dependent protein kinase and dephosphorylation of the 22,000-dalton phosphoprotein in these membranes. Dephosphorylation of the 22,000-dalton phosphoprotein can be attributed to a phosphoprotein phosphatase in the sarcoplasmic reticular membranes. This membrane-bound phosphoprotein phosphatase may play a role in the reversal of the relaxation-promoting effect of catecholamines on the heart.
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PMID:Phosphoprotein phosphatase-catalyzed dephosphorylation of the 22,000-dalton phosphoprotein of cardiac sarcoplasmic reticulum. 20 87


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