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:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of parathyroid hormone and calcitonin on the renal excretion of phosphate, calcium, and cyclic AMP was evaluated in the thyroparathyroidectomized hamster, a mammal apparently reisstant to the phosphaturic effect of parathyroid hormone. Parathyroid hormone did not increase phosphate excretion, although it decreased excretion of calcium and increased urinary excretion of cyclic AMP. This lack of a phosphaturic response to parathyroid hormone was not reversed by administration of 25-OH vitamin D or infusions of calcium or phosphate. Calcitonin, another potentially phosphaturic hormone, also vailed to increase phosphate excretion but markedly elevated urinary excretion of cyclic AMP. In hamsters pretreated with infusion of urinary ammonium chloride, which decreased plasma and urinary pH, both parathyroid hormone and calcitonin increased excretion of phosphate as well as that of cyclic AMP. Acetazolamide had no phosphaturic effect in ammonium chloride-loaded hamsters, and it decreased cyclic AMP and calcium excretion. Alkalinization of urine by acetazolamide did not prevent the phosphaturic effect of parathyroid hormone in ammonium chloride-loaded hamsters, but it blocked the increase in urinary cyclic AMP excretion. Parathyroid hormone and calcitonin both stimulated adenylate cyclase in a cell-free system (600-g pellet) from hamster renal cortex, elevated tissue cyclic AMP levels, and activated protein kinase in tissue slices from hamster renal cortex. In acid medium, the increase in cyclic AMP and activation of protein kinase in response to parathyroid hormone was diminished, but addition of acetazolamide restored responsiveness of both parameters to control values. Acetazolamide, on the other hand, did not influence adenylate cyclase or its response to parathyroid hormone or cyclic AMP phosphodiesterase activity. We conclude that the lack of a phosphaturic effect of parathyroid hormone and calcitonin in the hamster depends on steps in the cellular action of these hormones, steps that are sensitive to pH subsequent to cyclic AMP generation and protein kinase activation. In addition, acetazolamide may potentiate the phosphaturic effect of parathyroid hormone by promoting accumulation of cyclic AMP in tissue. Thus, the hamster is a particularly useful model for studies of syndromes in which there is renal resistance to phosphaturic hormones.
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PMID:Mechanism of resistance to the phosphaturic effect of the parathyroid hormone in the hamster. 1 74

The effect of an inhibitor of adenylate cyclase (ACI) was measured on some enzymes associated with cyclic nucleotide-regulated metabolism. Soluble guanylate cyclase was inhibited; both soluble and particulate cyclic GMP-phosphodiesterases were stimulated. Cyclic AMP phosphodiesterases were unaffected. In contrast, the activities of Na, K-ATPase, protein kinase, phosphorylase kinase, glycogen synthetase and a number of glycosidases were not altered by equipotent amounts of the inhibitor. It is concluded that this substance acts as a modulator of both cyclic AMP and cyclic GMP metabolism in heart and other tissues.
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PMID:The effect of adenylate cyclase inhibitor (ACI) on guanylate cyclase, phosphodiesterase and other enzymes in heart. 1 79

Identification and characterization of hormone receptors on the cell surface is an effective tool for studying the plasma membrane. Using the direct binding of a radiolabeled antagonist, (-)[3H]alprenolol, to crude membrane preparations, and a physiological response (cellular cyclic AMP levels), I demonstrated a catecholamine (beta-adrenergic) hormone receptor site coupled to a catecholamine responsive adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] on 3T3 and simian virus 40 (SV40)-transformed 3T3 cells. At a concentration of 1 muM, epinephrine and isoproterenol elevate cellular cyclic AMP levels 8- and 12-fold, respectively, in both cell lines. Norepinephrine was also a potent agonist on 3T3 cells (8-fold stimulation), but SV3T3 cells showed a lesser (2-fold) response to this hormone. The specificity of the physiological response (as well as the direct binding studies using the alprenolol radiolabel) is indicated by the increased effectiveness of (-) compared to (+) stereoisomers, rapid and reversible kinetics (steady state within 2 min), high affinity (Kd approximately 30 nM) and saturability (indicating a finite number of hormone receptors). These hormone receptor studies indicate the 3T3 cells have a beta1 adrenergic receptor while the SV3T3 cells have a receptor with beta2 qualities. In addition, the number of beta-adrenergic hormone receptors appear to be increased in the normal 3T3 cells by approximately 2-fold over the SV3T3 cells (300 versus versus 120 femtomol/mg of protein).
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PMID:Catecholamine hormone receptor differences identified on 3T3 and simian virus-transformed 3T3 cells. 1 52

Cyclic AMP levels were measured in cardiac and vascular tissues removed from pentobarbitone-anesthetized rats pretreated with theophylline 45 mg/kg i.p. Noradrenaline, 20 microng/kg i.v., increased cardiac but not vascular cyclic AMP levels; this selective effect of noradrenaline was not altered by pretreatment with phenoxybenzamine, 1 mg/kg i.v. Tazolol, 120 microng/kg i.v., selectively increased cardiac cyclic AMP levels whereas fenoterol, 15 microng/kg i.v., selectively increased vascular cyclic AMP levels. The results suggest that adenylate cyclase activation in cardiac and vascular tissued in vivo is mediated by beta adrenoceptors which consist of different subtypes.
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PMID:Selective activation of cardiovascular adenylate cyclase in vivo. 1 26

1. A factor which modulates the activity of cyclic AMP-dependent protein kinase copurifies from rat adipocytes with an inhibitor of adenylate cyclase. Purification and stability studies suggest that both effects reside in a single factor previously referred to as a feedback regulator. 2. The magnitude and direction of the feedback regulator effect on cyclic AMP-dependent protein kinase activity was dependent on the concentration of feedback regulator and the concentration and type of protein substrate. Using histone type IIA as substrate, feedback regulator was inhibitory at low histone concentrations and stimulatory at high concentrations. Preincubation of protein kinase with feedback regulator resulted in inhibition at all histone concentrations. With some protein substrates, e.g. histone f2b and casein, inhibition was observed at all histone concentrations. 3. The stimulation of histone type IIA phosphorylation resulted from an increased V with no effect on either the apparent Ka for cyclic AMP or the Km for ATP. Time course studies suggest that feedback regulator increased the rate of phosphorylation without increasing the total number of phosphorylation sites. Increased histone phosphorylation was observed regardless of whether the cyclic AMP-dependent protein kinase was peak I or peak II (off Deae-cellulose), isolated from bovine or rabbit skeletal muscle or rat heart. A small stimulation was observed using cyclic GMP-dependent protein kinase. 4. These results indicate that feedback regulator can inhibit or stimulate protein kinase, an effect which is probably substrate directed, and depends on the reaction conditions. Whether feedback regulator modulated protein phosphorylation in vivo in addition to its inhibition of adenylate cyclase is unknown. However, stimulation of protein kinase activity in the presence of cyclic AMP is a valuable and rapid assay for monitoring feedback regulator fractions during purification procedures.
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PMID:Modulation of protein phosphorylation by a factor purified from adipocytes. 1 26

The use of a competitive protein-binding assay for cyclic AMP, utilizing the binding protein purified from bovine adrenal cortex, for the study of adenylate cyclase activity of the washed 600 g sediment of bovine corpus luteum is validated. A specific assay for cyclic AMP could only be achieved by removal of the degradation products of ATP on a precipitate of nascent BaSO4. Simple dilution of the sample before assay was not sufficient to eliminate interference from degradation products of ATP. An observed variability in optimal ATP substrate and tissue concentrations is though to reflect variability in the enzymic profile of the cyclic corpus luteum. Optima with respect to F-, Mg2+ and pH are more clearly defined and are similar to those reported for adenylate cyclase systems for other tissues.
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PMID:Use of a competitive protein-binding assay for adenosine 3':5'-phosphate for the study of bovine corpus luteum adenylate cyclase. 1 71

A novel variant of the S49 mouse lymphoma has been selected from wild-type cells by growth in medium containing the beta-adrenergic agonist terbutaline and inhibitors of cyclic nucleotide phosphodiesterase. In contrast to the situation in the wild-type clone, synthesis of adenosine 3':5'-monophosphate (cyclic AMP) is not stimulated by beta-adrenergic agonists or by prostaglandin E1 either in intact variant cells or in membrane preparations of such clones. However, basal and NaF-stimulated activities of adenylate cyclase [ATP pyrophosphate-lyase (cyclizine), EC 4.6.1.1] are normal, enzyme activity is stimulated by guanyl-5'-yl imidodiphosphate [Gpp(NH)p], and intact cells accumulate cyclic AMP when exposed to cholera toxin. Furthermore, variant cell membranes possess ligand-binding activity consistent with the conclusion that a normal or an excessive number of beta-adrenergic receptors is present. Thus, interaction between the hormone-binding and the catalytic moieties of the adenylate cyclase system is lost. This variant phenotype, designated as uncoupled (UNC), has been stable for more than 100 generations without exposure to the drugs used for selection. Such cells should be useful for the elucidation of methanisms of transmission of information from hormone receptors to adenylate cyclase.
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PMID:Adenylate cyclase permanently uncoupled from hormone receptors in a novel variant of S49 mouse lymphoma cells. 1 19

Canine marrow erythroid colony growth is enhanced by agents linked to the adenyl cyclase/cyclic AMP (cAMP) system, including cAMP, a phosphodieterase inhibitor (RO-20-1724), cholera enterotoxin, and beta-adrenergic agonists. The adrenergic effect is mediated by receptors having beta2-subspecificity. These receptors are distinct from putative receptors for erythropoietin and those acted upon by cholera enterotoxin. In addition, the population of cells most responsive to beta-agonists is distinct from the majority of erythropoientin-responsive cells, perhaps representing a subpopulation of this class of cell. This demonstration of an adenyl cyclase-linked mechanism regulating mammalian erythroid colony growth provides a model for the modulation by other hormones or small molecules of in vitro and, perhaps, in vivo erythropoiesis.
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PMID:Modulation of in vitro erythropoiesis. The influence of beta-adrenergic agonists on erythroid colony formation. 1 18

1. The 3':5'-cyclic AMP phosphodiesterase in the microsomal fraction of baker's yeast is highly specific for cyclic AMP, and not inhibited by cyclic GMP, cyclic IMP or cyclic UMP. Catalytic activity is abolished by 30 micrometer-EDTA. At 30 degrees C and pH8.1, the Km is 0.17 micrometer, and theophylline is a simple competitive inhibitor with Ki 0.7 micrometer. The pH optimum is about 7.8 at 0.25 micrometer-cyclic AMP, so that over the physiological range of pH in yeast the activity changes in the opposite direction to that of adenylate cyclase [PH optimum about 6.2; Londesborough & Nurminen (1972) Acta Chem. Scand. 26, 3396-3398].2. At pH 7.2, dissociation of the enzyme from dilute microsomal suspensions increased with ionic strength and was almost complete at 0.3 M-KCl. MgCl2 caused more dissociation than did KCl or NaCl at the same ionic strength, but at low KCl concentrations binding required small amounts of free bivalent metal ions. In 0.1 M-KCl the binding decreased between pH 4.7 and 9.3. At pH 7.2 the binding was independent of temperature between 5 and 20 degrees C. These observations suggest that the binding is electrostatic rather than hydrophobic. 3. The proportion of bound activity increased with the concentration of the microsomal fraction, and at 22 mg of protein/ml and pH 7.2 was 70% at I0.18, and 35% at I0.26. Presumably a substantial amount of the enzyme is particle-bound in vivo. 4. At 5 degrees C in 10 mM-potassium phosphate, pH 7.2, the apparent molecular weight of KCl-solubilized enzyme decreased with enzyme concentration from about 200 000 to 40 000. In the presence of 0.5M-KCl, a constant mol.wt. of about 55 000 was observed over a 20-fold range of enzyme concentrations.
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PMID:Characterization of an adenosine 3':5'-cyclic monophosphate phosphodiesterase from baker's yeast. Its binding to subcellular particles, catalytic properties and gel-filtration behaviour. 1 35

Electrical stimulation of either the parasympathetic or the sympathetic nerve supply to the parotid and submaxillary glands increases the intracellular level of cyclic GMP and the rate of DNA synthesis and cell division while only sympathetic stimulation raises cyclic AMP levels. The periods of electrical stimulation inducing hyperplasia also raise the cyclic GMP concentration but there is no similar correlation with changes in cyclic AMP levels. However, the extent of hyperplasia induced by parasympathetic and sympathetic stimulation is not directly related to the size of the increase in cyclic GMP concentration that these treatments produce. Changes in cyclic AMP levels are reflected in altered in vitro adenylate cyclase activity. This activity is raised after 2 min sympathetic stimulation and markedly decreased with 30 min sympathetic or parasympathetic stimulation. Guanylate cyclase activity shows no such changes with nerve stimulation.
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PMID:Effect of electrical stimulation of the autonomic nerves on the levels and synthesis of cyclic nucleotides in the rat salivary glands: relationship to enhanced growth. 1 94


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