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:2.7.11.11 (AMPK)
12,425 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have studied the effects of adenosine 3':5'-monophosphate (cAMP)-dependent protein kinase on the phosphorylative and functional modification of bovine adrenal tyrosine hydroxylase. Incubation of partially purified tyrosine hydroxylase with cAMP-dependent protein kinase in the presence of [gamma32P]ATP and 5 micron cAMP led to a 3- to 5-fold activation of tyrosine hydroxylase and to incorporation of [32P]phosphate into protein. When tyrosine hydroxylase preparations activated by exposure to enzymatic phosphorylating conditions were analyzed by sucrose density gradient centrifugation, polyacrylamide gel electrophoresis, and gel electrofocusing, the radioactivity of 32P was coincident with the activity of tyrosine hydroxylase, suggesting incorporation of 32P from [gamma-32P]ATP into tyrosine hydroxylase. Polyacrylamide gel electrophoresis of the phosphorylated tyrosine hydroxylase preparation in the presence of 0.1% sodium dodecyl sulfate revealed that the 60,000-dalton polypeptide subunit of tyrosine hydroxylase served as the phosphate acceptor.
...
PMID:In vitro phosphorylation of bovine adrenal tyrosine hydroxylase by adenosine 3':5'-monophosphate-dependent protein kinase. 3 70

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.
...
PMID:Studies on the mechanism of phosphorylation of synthetic polypeptides by a calf thymus cyclic AMP-dependent protein kinase. 20 Sep 11

The recently discovered heat-stable inhibitor protein of the Ca2+-activated cyclic nucleotide phosphodiesterase (Sharma, R. K., Wirch, E. & Warg, J. H. (1978) J. Biol. Chem., in press) has been purified 238 214-fold from bovine brain extract using an affinity column of the modulator protein--Sepharose 4B conjugate. The purified sample appears to be homogeneous as judged by sodium dodecyl sulphate (SDS) gel electrophoresis. The protein band has a mobility corresponding to that of a polypeptide of molecular weight 68 000. Since the heat-stable inhibitor protein has a molecular weight of 70 000 under nondenaturing conditions, it suggests that it is a monomeric protein. The protein has no inhibitory activity toward the cAMP-dependent protein kinase or protein phosphatase. The purified sample has been tested for various enzyme activities which include ATPase, GTPase, cAMP phosphodiesterase, cGMP phosphodiesterase, 5'-nucleotidase, and protein kinase. None of these activities are exhibited by the purified sample.
...
PMID:Purification of the heat-stable inhibitor protein of the Ca2+-activated cyclic nucleotide phosphodiesterase by affinity chromatography. 20 31

A system of translational control in eukaryotes consists of (a) a proinhibitor and (b) an inhibitor of polypeptide chain initiation. The inhibitor (active eIF-2 kinase), a cAMP-independent protein kinase, catalyzes the phosphorylation by ATP of the small subunit of the polypeptide chain initiation factor eIF-2. This blocks the interaction of eIF-2 with eIF-2 stimulating protein (ESP) without which eIF-2 is unable to form an initiation complex, a prerequisite for translation. Our observations are consistent with the view that the proinhibitor (inactive eIF-2 kinase) is converted to the inhibitor by phosphorylation catalyzed by a cAMP-dependent protein kinase. This is analogous to the conversion of inactive phosphorylase kinase to active phosphorylase kinase. As in the case of phosphorylase kinase and phosphorylase, the modification of activity produced by phosphorylation of eIF-2 kinase and eIF-2 itself is probably reversed by dephosphorylation catalyzed by specific protein phosphatases (see diagram in Fig. 12) but no evidence bearing on this aspect of the problem is yet available. Hemin inhibits the cAMP-induced dissociation of the regulatory and catalytic subunits of cAMP-dependent protein kinase by binding to the regulatory subunit of the enzyme and blocking, through an allosteric effect, the binding of cAMP. Thus, hemin prevents the activation of eIF-2 kinase by inhibiting the cAMP-dependent protein kinase.
...
PMID:Regulation of protein synthesis. 22 49

The catalytic subunit of cyclic 3':5'-AMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) inhibits translation in Artemia salina and wheat germ extracts. It acts, as in reticulocyte lysates [Datta, A., de Haro, C., Sierra, J. M. & Ochoa, S. (1977) Proc. Natl. Acad. Sci. USA 74, 1463-1467] by catalyzing the conversion of a proinhibitor to an inhibitor of polypeptide chain initiation. Addition of ATP and either cyclic AMP or catalytic subunit promotes the proinhibitor-inhibitor conversion in crude proinhibitor preparations from A. salina embryos. The effect of cyclic AMP is due to stimulation of cyclic AMP-dependent protein kinase, present in such preparations, and is inhibited by hemin. In similar preparations from wheat germ, addition of ATP and catalytic subunit promoted proinhibitor-inhibitor conversion, but addition of ATP and cyclic AMP has little or no effect. As assayed with histone as substrate, wheat germ preparations exhibit a protein kinase activity that is not stimulated by the addition of cyclic AMP or cyclic GMP. Our results suggest that a translational control system, similar to that existing in rabbit reticulocytes and other mammalian cells, is present in organisms evolutionarily far removed from mammals.
...
PMID:Translational control by protein kinase in Artemia salina and wheat germ. 27 Jun 77

Incubation of reticulocyte lysates or isolated crude ribosomes with low levels of double-stranded RNA (0.1-10 ng/ml) induces the formation of an inhibitor of protein synthesis initiation similar to that observed in heme deficiency. The inhibitor is associated with a cyclic AMP-independent protein kinase activity (ATP:protein phosphotransferase, EC 2.7.1.37) that phosphorylates the small polypeptide (38,000 daltons) of the eukaryotic initiation factor eIF-2. Activation of the inhibitor requires ATP in addition to double-stranded RNA and is accompanied by the phosphorylation of a 67,000-dalton polypeptide of unknown function. The inhibitor remains associated with the ribosomes during high-speed sedimentation. Once formed, the ribosome-associated inhibitor phosphorylates eIF-2 and inhibits protein synthesis in the absence of double-stranded RNA. Inhibition is prevented by exogenous eIF-2. The bound inhibitor can be solubilized by extraction with 0.5 M KCl. The soluble inhibitor preparation retains the ability to phosphorylate the small polypeptide of eIF-2 and to inhibit protein synthesis. Untreated crude ribosomes also contain cyclic AMP-independent protein kinase activities that phosphorylate the middle polypeptide (49,000 daltons) of eIF-2 and several polypeptide subunits of eIF-3 (160,000, 125,000, and 65,000 daltons); these kinase activities are not affected by double-stranded RNA and do not inhibit protein synthesis.
...
PMID:Regulation of protein synthesis: activation by double-stranded RNA of a protein kinase that phosphorylates eukaryotic initiation factor 2. 27 4

Phosphorylation of the rat brain ryanodine receptor was studied using a monoclonal antibody, Ry-1, against the cardiac ryanodine receptor. A large polypeptide with the same SDS-PAGE mobility as that of the canine cardiac receptor was detected in rat brain membranes by immunoblotting. The brain ryanodine receptor was solubilized from the microsomal membranes with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS), and more than 85% of the solubilized receptor was immunoprecipitated by Ry-1. Immunoprecipitated receptors were phosphorylated by cAMP-dependent protein kinase. The ryanodine receptor was also expressed in cultured fetal rat brain neurons and was phosphorylated by treating the cells with dibutyryl cAMP. The number of cells showing a caffeine-induced Ca2+ transient was increased significantly in the phosphorylating condition. These results suggest that the Ca channel activity of the brain ryanodine receptor is regulated by cAMP-dependent phosphorylation.
...
PMID:Cyclic AMP-dependent phosphorylation of the rat brain ryanodine receptor. 131 34

Pure cGMP-inhibited cAMP phosphodiesterase (cGI-PDE) in micrograms quantities was isolated from bovine aortic smooth muscle after more than 5000-fold purification using DEAE ion-exchange and affinity chromatography with a derivative of the specific cGI-PDE inhibitor cilostamide conjugated as a ligand to aminoethyl agarose (CIT-agarose). The cGI-PDE, which constituted about half of the high affinity cAMP-PDE activity of a tissue homogenate, was identified with a 105-kDa protein on SDS-PAGE through use of antibodies towards the human platelet, bovine cardiac and bovine adipose tissue cGI-PDE in Western blot and immunoprecipitation/immunoinactivation analysis. As observed during purification of the enzyme from other tissues the enzyme protein was exquisitely sensitive to proteolytic nicking during purification, resulting in several 30-77-kDa polypeptide fragments. Rapid immunoprecipitation from fresh tissue extracts was the only was found to partially prevent the proteolysis. The native enzyme had apparent molecular sizes of approx. 100,000 or, mainly approx. 220,000 by gel chromatography, presumably indicating the presence of monomeric and dimeric forms. The enzyme hydrolyzed cAMP and cGMP with normal Michaelis-Menten kinetics with Km of 0.16 and 0.09 microM, respectively, with Vmax for hydrolysis of cAMP of 0.3 compared to 3.1 mumol/min per mg protein for cAMP. The enzyme was potently and selectively inhibited by cGMP (IC50 approximately 0.25 microM) and the cardiotonic/vasodilatory drugs OPC-3911 (a cilostamide derivative), milrinone and CI-930 (IC50 approximately 0.05, 0.40 and 0.25 microM, respectively). The cGI-PDE was phosphorylated by cAMP-dependent protein kinase as has been reported for the analogous enzymes in heart, adipose tissue and platelets. The identification of a cGI-PDE in the aortic smooth muscle and its inhibitor specificity is consistent with the hypothesis that inhibition of this enzyme is important in the mechanism through which these drugs produce vasorelaxation.
...
PMID:Purification and properties of the cGMP-inhibited cAMP phosphodiesterase from bovine aortic smooth muscle. 131 3

The phosphorylation of the alpha-subunit of Na+/K(+)-transporting ATPase (Na,K-ATPase) by cAMP-dependent protein kinase (PKA) and protein kinase C (PKC) was characterized in purified enzyme preparations of Bufo marinus kidney and duck salt gland and in microsomes of Xenopus oocytes. In addition, we have examined cAMP and phorbol esters, which are stimulators of PKA and PKC, respectively, for their ability to provoke the phosphorylation of alpha-subunits of Na,K-ATPase in homogenates of Xenopus oocytes. In the enzyme from the duct salt gland, phosphorylation by PKA and PKC occurs on serine and threonine residues, whereas in the enzyme from B. marinus kidney and Xenopus oocytes, phosphorylation by PKA occurs only on serine residues. Phosphopeptide analysis indicates that a site phosphorylated by PKA resides in a 12-kDa fragment comprising the C terminus of the polypeptide. Studies of phosphorylation performed on homogenates of Xenopus oocytes show that not only endogenous oocyte Na,K-ATPase but also exogenous Xenopus Na,K-ATPase expressed in the oocyte by microinjection of cRNA can be phosphorylated in response to stimulation of oocyte PKA and PKC. In conclusion, these data are consistent with the possibility that the alpha-subunit of Na,K-ATPase can serve as a substrate for PKA and PKC in vivo.
...
PMID:Phosphorylation of Na,K-ATPase alpha-subunits in microsomes and in homogenates of Xenopus oocytes resulting from the stimulation of protein kinase A and protein kinase C. 133 Oct 53

The multienzyme polypeptide CAD is phosphorylated at two sites by cyclic AMP (cAMP)-dependent protein kinase. Site 2 has two interesting features: it is located in a 'linking region' between two discretely folded enzyme domains, and a histidine, instead of the more usual arginine, is found three positions N-terminal to the phosphorylated serine. A synthetic peptide corresponding to the sequence around site 2 has an extended or random structure in solution, and the proton n.m.r. chemical shift of the histidine residues can be titrated against pH in the range 6.0-8.0. The peptide is phosphorylated more rapidly by cAMP-dependent protein kinase at lower pH values, indicating that the protonated histidine side chain corresponds to the arginine in the consensus recognition sequence for the kinase. Kemptide, a specific synthetic substrate for the kinase, was phosphorylated with a higher affinity and at a similar rate at all pH values. CAD was a better substrate than the synthetic peptide, and labelling was not affected by the pH of the incubation conditions. The results indicate that the phosphorylation site in the interdomain linker is sufficiently exposed to the solvent to ensure accessibility to the kinase, but that secondary or tertiary structure in the intact protein allows the histidine residue to remain protonated at physiological pH and enhances recognition of the phosphorylatable serine residue.
...
PMID:A protonated histidine residue in a phosphorylation site for cyclic AMP-dependent protein kinase. Comparison of a synthetic peptide with the exposed linking region in the multienzyme polypeptide CAD. 135 77


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

---