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)

Exposure of platelets to 1 C led to a transient increase in cyclic AMP levels (determined either by a protein binding method or by radioimmunoassay) within five to ten minutes reaching a maximum 10 to 15 minutes after chilling was begun and returning subsequently to baseline values. Addition of EDTA to the platelet suspension medium prevented this increase. Rewarming at 37 C produced a sudden reduction in platelet cyclic AMP. To determine whether the cold-induced increase in cyclic AMP was due to a transient stimulation of platelet adenylate cyclase or a rapid inhibition of phosphodiesterase, these enzymes were assayed in ruptured platelet suspensions. Platelet adenylate cyclase activity was found to possess certain characteristics similar to those of the enzyme derived from other sources but there was a marked potentiation of fluoride-stimulated adenylate cyclase activity by 0.001 M EDTA. This effect was limited to low EDTA concentrations. Exposure of platelets to 1 C for up to 60 minutes did not increase adenylate cyclase activity but lowered it substantially compared with controls kept at room temperature. Phosphodiesterase activity at 1 C was depressed sooner and to a greater extent than was adenylate cyclase. The transient rise in cyclic AMP levels in chilled platelets appears to be due to a disproportionate reduction of cyclic nucleotide phosphodiesterase activity.
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PMID:Effect of chilling on platelet cyclic adenosine 3:5-monophosphate and adenylate cyclase activity. 17 53

These studies evaluated the influence of an initial exposure of thyroid slices to thyroid-stimulating hormone (TSH) on the subsequent responsiveness to the hormone. Bovine thyroid slices were incubated with or without 50 mU/ml TSH for varying periods and then incubated in hormone-free medium for varying periods. Subsequently, slices were incubated for 20 min with 10 mM theophylline and with or without TSH. Cylic AMP was measured after the third incubation. Phosphodiesterase and adenylate cylase were assayed in homogenates prepared from slices after the second incubation. In some experiments prostaglandin E1, puromycin, thyroxine, and triiodothyronine and propylthiouracil were included in the media. In other experiments, low does of TSH (1 AND 10 mU/ml) were used instead of 50 mU/ml. Slices previously exposed to TSH have decreased responsiveness of the adenylate cyclase-cylic AMP system. Such refractoriness is hormone specific since initial exposure to prostaglandin E1 decreases the subsequent response to this substance but not to TSH. Refractoriness to TSH develops only when the first incubation is at least 30 min. It is not reversed by 5 h of incubation without hormone. Incubation of thyroid slices with puromycin does not eliminate refractoriness. The decreased response to TSH cannot be explained by release of thyroxine, triiodothyronine, or iodide from the slices. Phosphodiesterase activity is not increased during the refractory period. The decreased cyclic AMP response to TSH is associated with diminished response of adenylate cyclase activity to the hormone. Guanosine triphosphate (1 mM) increased adenylate cyclase activity in both control and TSH treated tissue, but the effect was significantly less in the latter. Although with guanosine triphosphate, TSH increased adenylate cyclase activity in TSH treated tissue, the enzyme activity was still less than that present in control tissue incubated with guanosine triphosphate and TSH. NaF caused an equivalent stimulation of adenylate cyclase in both control and TSH treated tissue. These results suggest that the refractoriness represents an alteration in hormone binding or the coupling of the bound hormone to the adenylate cyclase activity rather than any modification of the catalytic site of the enzyme.
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PMID:Exposure of thyroid slices to thyroid-stimulating hormone induces refractoriness of the cyclic AMP system to subsequent hormone stimulation. 17 52

Phosphodiesterase is shown to occur in ram semen, and its activity to be higher in spermatozoa than in seminal plasma. Using similar substrate levels, the rate at which adenosine 3',5'-monophosphate (cyclic AMP) is metabolized by phosphodiesterase in spermatozoa is about 100 times higher than that of cyclic AMP synthesis by adenylate cyclase. In spermatozoa, phosphodiesterase is present partly in a soluble form, and partly bound; both forms can be extracted by sonication. The soluble enzyme (pH optimum 8-0, Km = 1-5 muM, mol. wt 165,000) occurs as a single isoenzyme, as shown by polyacrylamide gel electrophoresis and anion-exchange chromatography; this isoenzyme appears to be specific for spermatozoa and its formation in the testis coincides with the appearance of spermatozoa. The bound sperm enzyme has been solubilized with Trion X-100; it is a single isoenzyme (pH optimum 8-0, mol. wt 165,000) which is electrophoretically different from the soluble form, but similar to the phosphodiesterase found in other tissues. Seminal plasma phosphodiesterase (pH optimum 8-8, mol. wt 165,000) is present in the form of three isoenzymes; all three are different from the two forms of sperm phosphodiesterase, but are similar to the isoenzymes found in certain male accessory organs.
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PMID:Investigations on adenosine 3',5'-monophosphate phosphodiesterase in ram semen and initial characterization of a sperm-specific isoenzyme. 17 69

The present study was initiated to determine whether specific hormones would influence adenylate cyclase activity within the maxillary-palatal complex during formation of the hamster secondary palate. Stages from initial appearance of the palatal processes to shortly after birth were studied. Highest basal adenylate cyclase activities occurred during the earliest periods of palate development. This basal enzyme activity began to diminish as palatal fusion occurred and remained lowered until birth. Activation of adenylate cyclase by fluoride was maximal at concentrations of 5-10 mM, and was observed throughout the span of palatal development. Fluoride activation of adenylate cyclase was greatest prior to fusion of the palatal processes, then decreased until birth when a slightly increased enzymatic stimulation was seen. Norepinephrine and epinphrine were the catecholamines most capable of inducing increased activation of adenylate cyclase at most periods of palatal growth. Increased enzyme activity in the presence of norepinephrine was more susceptible to antagonism by the beta adrenergic agent, propranolol, than to the alpha adrenergic agent, phentolamine. The remaining catecholamines, namely isoproterenol and dopamine, displayed a lesser ability to activate the enzyme, and adenylate cyclase was not equally responsive to these catecholamines at identical developmental stages. Other hormones, i.e. histamine, serotonin, thyrotropin, growth hormone, thyroxine and glucagon were generally ineffective in activating the enzyme. Phosphodiesterase activity was not detected until shortly before birth.
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PMID:Catecholamine-sensitive adenylate cyclase in the developing golden hamster palate. 17 49

Cyclic AMP levels and adenylate cyclase and phosphodiesterase activities were measured in control and ovalbumin-sensitized guinea pig lungs. Cyclic AMP levels were raised by epinephrine (0.01-10 mug/ml) in both control and sensitized lungs; the response being larger in the former group. Epinephrine (10(-9) -10(-6) M) stimulated adenylate cyclase in sensitized but had only a minimal effect in control preparations. Phosphodiesterase activities were equal in both groups. The hypersensitivity of adenylate cyclase response to epinephrine concurrent with diminished accumulation of cyclic AMP in sensitized guinea pigs indicate that antigen sensitization alters the response of the cyclic AMP system to epinephrine.
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PMID:Effect of epinephrine on cyclic AMP levels and adenylate cyclase and phosphodiesterase activities in control and antigen-sensitized guinea pig lungs. 19 Jun 22

Fat cell ghosts and homogenates of fat cells were used to study the influence of training on the regulatory system for lipolysis in adipose tissue of female rats. A training effect was identified from elevated succinate dehydrogenase activities in the soleus and plantaris muscles. Neither basal nor maximal (NaF-stimulated) adenylate cyclase activities per mg protein of fat cell ghosts were altered by training. Fluoride-stimulated adenylate cyclase activity per microgram DNA was lower in the trained than untrained group. Adenylate cyclase activities in response to norepinephrine expressed either on a per mg protein or per microgram DNA basis were lower (P less than 0.05) in fat cell ghosts from trained rats. Phosphodiesterase activity was higher (P less than 0.05) in fat cell ghosts from trained rats for cyclic AMP concentrations of 1--5.0 micrometer. The apparent Km's of phosphodiesterase were 1.19 and 2.0 micrometer of cyclic AMP for the untrained and trained groups, respectively (P less than 0.05). Protein kinase activity in the supernatant fraction of homogenates of fat cells was unchanged due to training. The overall effect of training was to blunt the system for cyclic AMP production in rat adipocytes. This may explain, at least partially, the lower plasma free fatty acid levels observed in trained compared to untrained persons during submaximal exercise.
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PMID:Effect of physical training on control mechanisms of lipolysis in rat fat cell ghosts. 19 25

Effect of chronic cadmium (Cd) exposure and the influence of diethyldithiocarbamate (DDC) on Cd absorption was studied on the brain of young male Wistar rats. A significant amount of Cd accumulated in cerebral cortices of rats after 4 weeks of Cd (6 mg/kg body wt) exposure (through gastric intubation). The biological activity of calmodulin (CaM) decreased significantly (p less than 0.001) in the cerebral cortices of these animals in comparison to the control group. 3'-5' Phosphodiesterase and synaptic membrane Ca(2+)-Mg(2+) ATPase were also significantly affected (p less than 0.01 and p less than 0.001 respectively). However, Cd treatment did not alter synaptic membrane adenylate cyclase activity and DDC (9.2 mg/kg body wt, intraperitoneal) treatment along with Cd (6 mg/kg body wt) enhanced Cd accumulation in cerebral cortices of treated animals resulting in an increased inhibition of CaM and CaM dependent enzymes. These data suggest that Cd may be acting via binding to CaM and uncoupling it from its normal cellular control of calcium.
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PMID:In vivo effects of cadmium on calmodulin and calmodulin regulated enzymes in rat brain. 165 64

The aim of the present study was to investigate the regulation of cAMP by tamoxifen in quail oviduct. A single injection of tamoxifen to immature female quails induced a transient activation of adenylate cyclase. Enzyme activity began to increase 3 h after the injection, peaked at 6 h and then dropped to control level at 12 h. The same time-response curves were observed following the injection of estradiol benzoate or estradiol benzoate + tamoxifen. Moreover, adenylcyclase exhibited the same sensitivity to exogenous activators (guanylylimidodiphosphate and forskolin) in the different treated groups. Phosphodiesterase activity was left unchanged during the prereplicative period and cAMP concentration was significantly increased at 6 h (+ 44.3%). Then, cAMP concentration continued to increase (+ 73.8% at 24 h) while cAMP phosphodiesterase and adenylcyclase activities remained at control levels. Injected concurrently with estradiol benzoate, tamoxifen completely inhibited the growth promoting effect of estradiol. Tamoxifen also inhibited the activation of adenylcyclase and cAMP phosphodiesterase induced by the hormone alone during the proliferative phase of the tissue. Moreover, the combined treatment led to a sustained elevation of cAMP in the oviduct, whereas estradiol benzoate alone decreased the level of cAMP. These results and those of our previous studies showing a significant correlation between the growth inhibitory potency of triphenylethylene derivatives in vivo and their efficiency to inhibit calmodulin-dependent cAMP phosphodiesterase in vitro, strongly suggest that the differential regulation of cAMP levels by estradiol and tamoxifen is essential for the growth promoting or growth inhibiting activities of these molecules.
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PMID:Growth inhibition and the regulation of cyclic AMP by the triphenylethylene anti-estrogen tamoxifen in the quail oviduct. 166 31

1. cAMP Phosphodiesterase activity and kinetic parameters (Km and Vmax) were measured in subcutaneous and perirenal adipocyte plasma membranes from Large White male and castrated pigs. The animals were fed a control low fat diet or a sunflower diet enriched with linoleic acid (C18:2 n-6). 2. Phosphodiesterase activity, low Km and Vmax were lowered by castration. 3. In animals fed the sunflower diet, phosphodiesterase activity decreased without affecting either Km or Vmax. 4. Phosphodiesterase activity was higher in perirenal sites than in subcutaneous ones, particularly in male pigs. This may be explained by a lower Km or a higher cAMP phosphodiesterase affinity to cAMP in perirenal sites. 5. Theophylline was a potent inhibitor of phosphodiesterase activity principally in perirenal sites. 6. The intermediate role of cAMP phosphodiesterase in adenylate cyclase activity and lipolytic processes is discussed.
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PMID:Effects of castration, dietary fat and adipose tissue sites on adipocyte plasma-membranes cyclic AMP phosphodiesterase activity in the pig. 166 23

C6-2B rat glioma cells were stably transfected with substance K receptor cDNA and used to study interactions between cAMP and Ca2+ signaling pathways. Activation of the newly expressed receptors by substance K increased the intracellular free Ca2+ concentration, as monitored by single-cell fura-2 imaging, and markedly inhibited agonist-stimulated cAMP accumulation. Blockade of intracellular Ca2+ mobilization abolished the substance K receptor-mediated inhibition of isoproterenol-induced cAMP production. Phosphodiesterase inhibitors, down-regulation or inhibition of protein kinase C, and pertussis toxin failed to prevent substance K-induced inhibition of agonist-stimulated cAMP accumulation. An increased intracellular Ca2+ concentration caused by either calcium ionophores or activation of endogenous bradykinin receptors was found to markedly reduce cAMP production in wild-type cells. These results demonstrate that elevated intracellular Ca2+ concentration can negatively modulate agonist-stimulated adenylate cyclase activity in C6-2B glioma cells.
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PMID:Inhibition of cAMP accumulation by intracellular calcium mobilization in C6-2B cells stably transfected with substance K receptor cDNA. 171 1


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