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

Two cAMP-independent acetyl-CoA carboxylase (ACC) protein kinases have been partially purified from rat liver cytosol and microsomal extracts. The first kinase, present in greatest activity in microsomal extracts, appears to be identical to casein kinase I by characteristic molecular size on gel filtration (Mr 40,000) and sodium dodecyl sulfate-gel electrophoresis (Mr 34,000), autophosphorylation of this single subunit, inability to efficiently utilize GTP, and resistance to inhibition by heparin and 2,3-diphosphoglycerate. The second kinase, predominant in cytosol, appears to be identical to casein kinase II by characteristic molecular size on gel filtration (Mr 150,000), an autophosphorylated subunit of Mr 25,000, a Km for GTP nearly equal to that of ATP, inhibition by heparin and 2,3 DPG, and relative substrate specificity. Despite the incorporation of up to 2 mol 32P/mol carboxylase subunit (kinase I) and 0.6 mol/subunit (kinase II), phosphorylation by either kinase causes no change in carboxylase activity. The site(s) phosphorylated by each kinase and by the cAMP-dependent protein kinase on carboxylase appear to be clustered on a Mr 16,000 cyanogen bromide peptide that is readily released on incubation with trypsin. The potential roles of these kinases in the regulation of ACC remain to be clarified.
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PMID:Phosphorylation of acetyl-coenzyme A carboxylase by casein kinase I and casein kinase II. 614 63

Isoproterenol-induced amylase release from rabbit parotid acini was examined in relation to cyclic AMP (cAMP) concentrations, cAMP-dependent protein kinase (cAMP-PK) activity ratios and protein phosphorylation. Initial stimulation of amylase release by isoproterenol was preceded by increases in cAMP, cAMP-PK activity ratios and phosphorylation of a 34,000 MW (major) and a 30,000 MW (minor) protein in the microsomal fraction. When propranolol was added, decreases in cAMP concentrations and cAMP-PK activity ratios preceded the reduction in amylase release. Detailed analysis was performed on the 34,000 MW protein. The relation of dephosphorylation of protein 34 and reduction in amylase release was complex. Slight dephosphorylation occurred before or concurrently with the decrease in amylase release; however, maximal dephosphorylation was preceded by maximal inhibition of amylase release. When secretion of amylase was reinstituted by isoproterenol or forskolin, increases in cAMP and cAMP-PK activity ratios occurred before or in concert with amylase release but rephosphorylation of protein 34 occurred after the start of amylase release. Photoaffinity labeling studies using [32P]-8-azidoadenosine-3',5'-cyclic monophosphate indicated that proteins 34 and 30 were not regulatory subunits of cAMP-PK or their breakdown products. Although these data are consistent with phosphorylation of proteins 34 or 30 being required for triggering initial secretion, maximum dephosphorylation was not essential for inhibition of secretion. Furthermore, initiation of amylase release by the gland after a short period of quiescence did not depend on prior phosphorylation of protein 34. These data may indicate the absence of a requirement of amylase release for phosphorylation of protein 34.
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PMID:Isoproterenol-induced amylase release in rabbit parotid acini: relation of protein phosphorylation, cyclic AMP and related kinase activity to changes in secretory rate. 620 8

Sarcomplasmic reticulum from rabbit fast skeletal muscle contains intrinsic protein kinase activity (ATP:protein phosphotransferase, EC 2.7.1.37) and a substrate. The protein kinase activity was Mg2+ dependent and could also phosphorylate exogenous protein substrates. Autophosphorylation of sarcoplasmic reticulum vesicles was not stimulated by cyclic AMP, neither was it inhibited by the heat-stable protein kinase inhibitor protein. The phosphorylated membranes had the characteristics of a protein with a phosphoester bond. An average of 73 pmol Pi/mg protein were incorporated in 10 min at 30 degrees C. Addition of exogenous cyclic AMP-dependent protein kinase increased the endogenous level of phosphorylation by 25-100%. Sarcoplasmic reticulum membrane phosphorylation, mediated by either endogenous cyclic AMP-independent or exogenous cyclic AMP-dependent protein kinase, occurred on a 100 000 dalton protein and both enzyme activities resulted in enhanced calcium uptake and Ca2+-dependent ATPase (ATP phosphohydrolase, EC 3.6.1.3), in a manner similar to cardiac microsomal preparations. Regulation of Ca2+ transport in skeletal sarcoplasmic reticulum may be mediated by phosphorylation of a 100 000 dalton component of these membranes.
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PMID:Phosphorylation of a 100 000 dalton component and its relationship to calcium transport in sarcoplasmic reticulum from rabbit skeletal muscle. 624 11

Spontaneously hypertensive rats (SHR) and Wistar-Kyoto normotensive rats (WKY) were compared for phosphorylation-dephosphorylation mechanism(s) in aorta, caudal artery, inferior vena cava, and right and left ventricles. Reduction of cAMP-induced phosphorylation of microsomes and cAMP-dependent protein kinase activity was significant in the aorta and caudal artery of SHR compared with WKY. These changes were not observed in the vena cava of SHR. Phosphoprotein phosphatase activity was significantly increased (p less than 0.05) in the soluble fraction of arterial smooth muscle. No changes were observed, however, in the myocardium or vein. Furthermore, the extent of phosphorylation, and Ca2+ uptake ability and the protein kinase activity in the soluble and the microsomal fractions were not reduced in the myocardium of SHR compared with WKY. These data suggest that phosphorylation-dephosphorylation mechanisms are altered in the microsomal fraction of the aorta and caudal artery of SHR, which may result in reduced Ca2+ uptake by the intracellular organelle. The changes observed could have a significant effect on vasodilatation of arteries in the hypertensive state. The lesion appears specific to the arterial smooth muscle in the cardiovascular tissues.
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PMID:Possible role of phosphorylation-dephosphorylation in the regulation of calcium metabolism in cardiovascular tissues of SHR. 624 68

The phosphorylation of rat adrenal protein components in response to adrenocorticotropin has been studied in adrenal quarters, isolated cells, and in vivo. In adrenal quarters, adrenocorticotropic hormone (ACTH)-stimulated phosphorylation or dephosphorylation of proteins was not affected by the presence of protein synthesis inhibitors despite a total inhibition of steroidogenesis. (The term dephosphorylation refers to an apparent decrease in the labeling of a particular protein with 32P at various times after the addition of ACTH. This may be due to enzymatic removal of phosphate or protein degradation or complexation of this protein with another cellular component.) Studies with isolated cell preparations identified several proteins that are phosphorylated or dephosphorylated in response to hormone. These changes in phosphorylation were also observed in adrenal quarters and correlated well with ACTH-stimulated steroidogenesis as determined by temporal analysis and dose-response studies of corticosterone production. In vivo injection of male hypophysectomized rats with [32P]phosphate and ACTH demonstrated changes in the labeling of six adrenal proteins. Many of the proteins phosphorylated in vivo were also demonstrated to be phosphorylated in both in vitro systems. Finally, the injection of a physiological dose of ACTH appeared to selectively activate the type I cAMP-dependent protein kinase within the microsomal fraction as determined by the binding of a photoaffinity-labeled reagent. These results suggest that alterations in phosphorylation of adrenal proteins in response to ACTH is proximal to or independent of the obligatory role of protein synthesis in acute steroidogenesis.
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PMID:The phosphorylation of adrenal proteins in response to adrenocorticotropic hormone. 626 22

A protein kinase with high specificity for histone H1 was purified from a plasmacytoma microsomal fraction by a high-salt wash, ammonium sulfate precipitation, chromatography on DEAE-cellulose, hydroxyapatite and Sephadex G-200 columns, and the main properties of this kinase were studied. A sulfhydryl compound, such as 2-mercaptoethanol or dithiothreitol, was necessary for full activity. The optimum pH was 7.4-7.8. After purification, the histone H1 kinase was not stimulated by cAMP or cGMP. It was not inhibited by the heat-stable cAMP-dependent protein kinase inhibitor from beef heart. It utilized preferentially GTP over ATP as phosphate donor. Km values for ATP and GTP were 58 microM and 1.4 microM respectively; the Km for histone H1 was 14 microgram ml-1. The molecular weight was approximately 90 000 by gel-exclusion chromatography. Analysis of the purified H1-specific protein kinase by polyacrylamide gel electrophoresis in dodecylsulfate showed two bands having molecular weights of approximately 64 000 and 54 000. Many characteristics of this kinase were similar to those of the chromatin-bound protein kinase reported by other workers in rapidly proliferating cells.
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PMID:Purification and characterization of a specific histone H1 protein kinase from mouse plasmacytoma. 626 46

cAMP modulates estrogen, hCG, and lactate syntheses by human placenta, cAMP presumably exerts its major intracellular effect by binding to cAMP-dependent protein kinase (cAMP-PK), which, in turn, phosphorylates regulatory proteins within the target cell. cAMP binding and cAMP-PK have not been previously identified in placenta. [3H]cAMP binding to crude cytosol fractions of term placenta was rapid, saturable, and reversible. Scatchard analyses of saturation experiments of [3H]cAMP binding to placental cytosol were linear (Kd = 1.13 +/- 0.11 x 10(-8) M; n = 5). The binding capacity was 1.27 +/- 0.18 pmol/mg protein. Competition for the [3H]cAMP-binding site followed the potency order cAMP much greater than cGMP much greater than (Bu)2cAMP, analogous to cAMP binding to cAMP-PK in other tissues. ADP, ATP, and adenosine did not compete for the [3H]cAMP-binding site. cAMP significantly enhanced phosphorylation of histone protein by placental cytosol (activity ratio, 0.57 +/- 0.04; P less than 0.01). Two peaks of [3H]cAMP binding and coincident cAMP-PK activity were identified by DEAE-cellulose column chromatography of placental cytosol corresponding to classical type I and type II cAMP-PK. While the majority of the cAMP-PK was found in placental cytosol, cAMP-PK was also demonstrated in crude microsomal and microvillous brush border membranes of human placenta after solubilization with Triton X-100 (P less than 0.05). Regulation of placental function by catecholamines and other hormones known to mediate cAMP levels may be accomplished through the phosphorylation of cellular proteins by cAMP-dependent protein kinases.
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PMID:Adenosine 3',5'-monophosphate (cAMP)-binding protein and cAMP-dependent protein kinase in human placenta. 630 Jan 72

Stimulation of secretion in exocrine cells by agonists involving cAMP as second messenger is associated with the phosphorylation of a specific membrane-associated 22.4-kDa protein (protein III) (Jahn et al.). Here it is shown by subcellular fractionation of rat parotid gland lobules that protein III is associated with the endoplasmic reticulum. The submicrosomal fractions containing protein III, also contain the ATP-dependent microsomal calcium pump activity. Protein III in microsomal subfractions can be phosphorylated in vitro with catalytic subunit from cAMP-dependent protein kinase. Phosphorylated protein III contains exclusively P-serine. Protein III can be removed from ER-membranes with acid chloroform-methanol or Triton X-114, but not by high salt wash indicating that it is tightly associated with the membranes. Protein III is smaller than phospholamban and, in contrast to phospholamban, resistant to heating in SDS. A relationship between phosphorylation of protein III and microsomal calcium sequestration is discussed.
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PMID:Specific phosphorylation of a protein in calcium accumulating endoplasmic reticulum from rat parotid glands following stimulation by agonists involving cAMP as second messenger. 631 93

Four lines of evidence presented here suggest that the activity of cholesterol 7 alpha-hydroxylase in rat liver is modulated by changes in its phosphorylation state. 1) Livers were homogenized and microsomes were isolated and washed in the presence of either 50 mM NaCl or 50 mM NaF, the latter an inhibitor of phosphoprotein phosphatases. The 7 alpha-hydroxylase activity of microsomes prepared with NaF was 80% greater than that of microsomes prepared with NaCl. 2) Incubation of 10,000 X g supernatants from rat liver for 20 min at 37 degrees C in the absence of 50 mM KF decreased the activity of microsomal cholesterol 7 alpha-hydroxylase by 52%. No significant change was seen in the presence of KF. 3) 7 alpha-Hydroxylase activity fell by 40% when microsomes were incubated with bacterial alkaline phosphatase compared to incubation of microsomes with phosphatase that was inhibited by phosphate and EDTA. 4) 7 alpha-Hydroxylase activity increased by 22% when phosphatase-treated microsomes were incubated for 40 min at 37 degrees C with 1 mM MgATP, 50 microM cAMP, and 200 units of cAMP-dependent protein kinase.
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PMID:Rat liver cholesterol 7 alpha-hydroxylase. Modulation of enzyme activity by changes in phosphorylation state. 706 45

Uptakes of radioactive C1- or 1- by gastric microsomal vesicles were stimulated 2- to 8-fold by AtP. The sensitivity of those uptakes to a C1- in equilibrium OH- ionophore and to osmotic swelling suggested they were due to transport rather than to binding. The ATP effect was labile, but dithiothreitol and methanol improved its stability. The stimulation of anion transport required magnesium; GTP and UTP were less potent than ATP whereas ADP and AMP had no effect. The apparent Km for ATP was estimated to be 2 X 10(-4) M at 22 degrees C. The rate of the ATP-dependent transport showed saturation-type kinetics, with half-maximal uptake at 10 mM for I- and 15 mM for C1-. Nonradioactive C1-, I-, and SCN- competed with 125I- uptake while SO42- did not. K+ valinomycin increased the ATP-dependent C1- uptake. The thermostable inhibitor of cAMP-dependent protein kinases inhibited the effect of ATP. These results suggest the existence of an anion conductance, permeant to C1-, I-, and SCN- and nonpermeant to SO42-, which could be linked to a cAMP-dependent protein kinase.
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PMID:C1-transport in gastric micorsomes. An ATP-dependent influx sensitive to membrane potential and to protein kinase inhibitor. 744 May 65


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