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)

Genetically obese (ob/ob) mice, mice that became obese after treatment with gold thioglucose, and lean animals were studied in the euthyroid state, after induction of hypothyroidism, and after treatment with triiodothyronine. The activity of glycerol 3-phosphate dehydrogenase (sn-glycerol-3-phosphate:(acceptor) oxidoreductase; EC 1.1.99.5] was reduced in the livers from hypothyroid animals and was increased by treatment with triiodothyronine in all groups. The activity of the ouabain-suppressible sodium- and potassium-dependent ATPase (ATP phosphohydrolase; EC 3.6.1.3) was increased by triiodothyronine and reduced by hypothyroidism in the lean and gold thioglucose-treated obese animals. In the obese (ob/ob) mice, on the other hand, treatment with triiodothyronine did not increase the activity of this enzyme, which remained at the level found in hypothyroid animals. This enzymatic activity was reduced in both liver and kidney. Adenylate cyclase [ATP pyrophosphate-lyase (cyclizing); EC 4.6.1.1] activity in liver membranes, however, was similar in all three groups of mice. This enzyme complex was activated by glucagon and was unaffected by treatment with thyroid hormones. The lack of a thyroid-dependent ouabain-suppressible (Na(+) + K(+))-ATPase in the tissues of the obese (ob/ob) mouse could explain most, if not all, of the abnormalities that have been described in this animal.
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PMID:An enzymatic defect in the obese (ob/ob) mouse: loss of thyroid-induced sodium- and potassium-dependent adenosinetriphosphatase. 14 80

The regulation of adrenergic receptors in rat heart was measured in rats made hyperthyroid by injection with thyroxine and made hypothyroid by addition of propylthiouracil to the drinking water. Hyperthyroid rats display cardiac hypertrophy and a decrease in epididymal fat pad weight. The maximal beta-receptor level of ventricular membranes, as determined by (-)-[3H]dihydroalprenolol binding, was increased 60% by thyroxine treatment and decreased about 30% by propylthiouracil treatment. The affinity of the beta receptor was unchanged after thyroxine or propylthiouracil treatment. The maximal activity of the isoproterenol-stimulated adenylate cyclase (EC 4.6.1.1) varied with thyroid state in a manner parallel to the increase in beta-adrenergic binding sites. Thyroxine treatment also increases by 2-fold the beta receptors in isolated rat fat cells. Propylthiouracil treatment lowered the level of alpha receptors in heart by 30% as measured by [3H]dihydroergocryptine binding, but increased the affinity about 2.5-fold. The highest level of alpha receptors was seen in control hearts. These studies indicate that thyroxine may control the turnover of beta-adrenergic receptors in heart and fat cells and regulate physiological responses in these tissues via a hormone-hormone interplay system. Thyroxine treatment reduced the activity of the membrane-bound Mg2+-ATPase (EC 3.6.1.3) and 5'-mononucleotidase (EC 3.1.3.5) but appears to increase the activity of the (Na+ + K+)ATPase (EC 3.6.1.4).
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PMID:Hormone action at the membrane level. VIII. Adrenergic receptors in rat heart and adipocytes and their modulation by thyroxine. 14 63

1. Pancreatic plasma membranes containing a high adenylate cyclase activity and a low contamination by cytochrome c oxidase were isolated from the rat by sucrose density centrifugation. The preparation contained an (Mg,Ca)-ATPase of high activity with the following characteristics. 2. The ATPase activity was shown to have two apparent Km values for Mg-ATP (0.24 +/- 0.09 mM and 1.15 +/- 0.21 mM) and two apparent Km values for Ca-ATP (0.14 +/- 0.09 mM and 0.68 +/- 0.10 mM). Mg-GTP and Ca-GTP were also hydrolysed by the preparation. The phase transition temperature was 19.3 +/- 1.0 degrees C for the Mg-ATPase and 22.6 +/- 1.1 degrees C for the Ca-ATPase activities. 3. Three lines of evidence suggest that Mg-ATP and Ca-ATP were substrates for the same enzyme: Mg-dependent and Ca-dependent activities were not additive; the two activities showed the same pH optimum at 8.0; and the nonionic detergents Triton X-100, Triton X-305, Triton N-101, Lubrol P 12 A, and digitonin, produced a parallel solubilization of the two activities. 4. Enzyme activities were insensitive to potassium, sodium, ouabain, pancreozymin, carbamoyl-choline, secretin, concanavalin A, wheat germ agglutinin, and soybean lectin.
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PMID:Characterization of (Mg,Ca)-ATPase activity in rat pancreatic plasma membranes. 15 27

Platelets were examined to enable a simultaneous investigation to be made of indolylamine and electrolyte metabolism in affective disorder. No significant differences were detected in either platelet membrane ATPase or adenyl cyclase specific activity in any of the groups of patients studied, when compared with appropriate controls. A reduced Vmax and y for the 5-hydroxy-tryptamine uptake process into platelets was observed in both unipolar and bipolar depressed groups. The Km for this process was not significantly different in any of the patients from that found in control subjects. Lithium therapy was shown not to influence significantly any of the platelet parameters examined. It is suggested that membrane enzyme changes found in some peripheral cells in patients suffering from affective disorder, i.e. reduced Na+ + K+ - ATPase activity in erythrocytes in depression, is not common to all peripheral cells and may or may not reflect central nervous system changes.
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PMID:Studies on human blood platelets in affective disorder. 15 82

The effects of sodium pentobarbital on ATPase, Ca2+ binding and adenylate cyclase activities of the rat heart sarcolemmal preparations were investigated. The Na+ - K+ ATPase activity was diminished by pentobarbital in concentrations as low as 0.3 mM. Mg2+ ATPase, Ca2+ ATPase and adenylate cyclase activities were also depressed but required 10 to 15 mM of this agent. Pentobarbital in concentrations of 10 mM, however, caused an increase in sarcolemmal Ca2+ binding. Mitochondrial and microsomal ATPase activities were decreased by 1 and 5 mM concentrations of pentobarbital respectively, while myofibrillar ATPase activity was unaltered even at a concentration of 20 mM. These data suggest that cardiodepressant effects of high doses of pentobarbital may partly be explained on the basis of its actions on heart sarcolemma.
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PMID:Effects of sodium pentobarbital on rat heart sarcolemma. 15 80

The purpose of this study was to determine whether the previously reported differences in adenylate cyclase activity between the sarcolemma of normal and dystrophic chick muscles are also found in the SR, to search for a possible relationship between the adenylate cyclase changes and the pathophysiology of dystrophy, and to investigate whether the findings can be extended to Duchenne human muscular dystrophy by studying the adenylate cyclase and ATPase activities of erythrocyte ghosts from DMD patients and carriers. Microsomes were separated by standard techniques from the pectoralis muscles of normal and dystrophic ckeckens of various ages. The microsomal yields were significantly larger in dystrophic muscles. Adenylate cyclase activities in dystrophic microsomes were higher than those in matched controls and increased with the progression of the disease. The ratio between the two rose from one at 2 weeks of age to nine at about 9--10 weeks. Kinetic analyses showed that the ks for MgATP2- was about 40 microM (at 3 mM Mg2+ and 0.3 mM Ca2+) both in normal and dystrophic microsomes, that calcium caused umcompetitive inhibition of the enzyme (Ki = 0.2 mM), that the effect of calcium was noncooperative (Hill coefficient, nH = 1), that calcium did not affect the cooperativity for MgATP2-, and that magnesium competitively removed the calcium inhibition and caused additional, cooperative stimulation of the enzymatic activity (ka = 1.5 mM; NH =2). The major difference between normal and dystrophic adenylate cyclase was a higher enzymatic velocity in the latter, suggesting a larger amount of enzyme. We investigated whether altered cAMP levels may effect calcium accumulation. Calcium uptake measured (in the presence of oxalate) at several ages revealed no difference between normal and dystrophic chickens. The extent of calcium binding was also similar, although the kd for Ca2+ was lower in dystrophic microsomes. Binding was enhanced in the presence of exogenous protein kinase, but the responses of normal and dystrophic tissues were similar. We concluded that the elevation of adenylate cyclase in dystrophy was not related to microsomal calcium accumultion. Ivestigation of the localization of microsomal adenylate cyclase supported this view. Separation of calcium-loaded microsomes on a discontinuous sucrose gradient into four fractions demonstrated that adenylate cyclase activity, measured in the presence of Lubrol-PX and EGTA, was inversely related to calcium-accumulating activity. Na+, K+-ATPase comigrated with adenylate cyclase. Highest specific activities were found in the lightest fraction. These observations were confirmed by histochemical studies. The reaction product from adenylate cyclase activity was present predominantly in the terminal cisternae of the SR. In the context of the literature, our findings suggest that the rises in adenylate cyclase and Na+, K+-ATPase in avian dystrophy are compensatory changes, elicited by a defect in ECC at the calcium release step...
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PMID:Adenylate cyclase in muscular dystrophy. 15 10

Basal adenylate cyclase activity was increased in red cell ghosts from both patients with Duchenne muscular dystrophy and their mothers when the activities were compared to proper age-matched controls. The activity of ATPase measured in the presence of Na+, K+, and Mg2+ was not found to be different in erythrocyte ghosts from Duchenne dystrophic patients, age-matched controls, or the mothers of Duchenne patients, and ouabain inhibited ATPase in ghosts to the same extent in all membrane preparations.
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PMID:Adenylate cyclase and ATPase activities in red cell membranes of patients and genetic carriers of Duchenne muscular dystrophy. 15 46

Studies were carried out to determine if the receptors for parathyroid hormone, calcitonin, and prostaglandin E1 could be differentiated in renal cortex. Slices of rabbit renal cortex were incubated in buffer containing theophylline for 1 hr and then in fresh buffer with and without hormone for an additional period of 15 to 30 min. Parathyroid hormone caused a marked increase in 3',5'-AMP in both the tissue and the reaction medium. The maximal increase in 3',5'-AMP in response to prostaglandin E1 was similar to that of parathyroid hormone in the tissue but significantly less in the medium. The maximal response to calcitonin was less in both the tissue and the medium. Addition of 200 mug/ml trypsin to the first incubation abolished the subsequent response to parathyroid hormone in both the tissue and the reaction medium but did not affect the basal concentration of 3',5'-AMP or the response to calcitonin or prostaglandin E1. Controls were carried out to show that the lack of response to parathyroid hormone could not be attributed to hydrolysis of the hormone by residual trypsin. Slices were also homogenized after preincubation with and without trypsin and assayed for adenylate cyclase activity. Incubation with trypsin markedly diminished the increase in enzyme activity in response to parathyroid hormone but did not alter the basal activity or the response to calcitonin or sodium fluoride. The response to prostaglandin E1 was significantly increased. Combinations of any two or the three hormones at maximal concentrations caused an additive increase in adenylate cyclase activity. The results indicate that the receptors for parathyroid hormone, calcitonin and prostaglandin E1 in renal cortex are separate and the receptor for parathyroid hormone can be selectively hydrolyzed by proteolytic digestion.
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PMID:Selective proteolysis of the receptor for parathyroid hormone in renal cortex. 16 81

The adenylate cyclase system present in a preparation enriched in plasma membranes derived from bovine adrenal cortex was investigated in considerable detail. This system is stimulated by adrenocorticotropic hormone (ACTH), by biologically active analogs of this hormone, and by fluoride ion. The preparation contains sodium-potassium- and magnesium-dependent ATPases that are markedly inhibited by 50 mM sodium fluoride. Incorporation of a pyruvate phosphokinase ATP generating system into the adenylate cyclase assay medium provided constant substrate levels. In the presence of the ATP generating system, the rate of cyclic AMP formation (basal, fluoride, and ACTH-activated) was proportional to enzyme concentration and was linear with time. Proportionality with respect to enzyme concentration as concerned the hormone-activated adenylate cyclase was achieved only when the ratio of hormone to enzyme protein was kept constant. The temperature optimum of the adenylate cyclase, basal or activated, was approximately 30 degrees. Michaelis-Menten kinetics were observed when the ratio of Mg2+ to ATP was approximately 6:1. Both calcium and ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid completely inhibited the adenylate cyclase system at concentrations of 5 and 0.5 mM, respectively. GTP was inhibitory at concentrations of 10-2 M but had little effect at lower concentrations. Freezing in liquid nitrogen and storage at -60 degrees exerted little effect on the fluoride-stimulated enzyme but lowered hormone stimulated activity. Preincubation in the presence of ACTH afforded a high degree of stabilization of the enzyme system while preincubation with a biologically inactive analog afforded no protection.
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PMID:Adenylate cyclase system of bovine adrenal plasma membranes. 16 47

Homogenate and plasma membrane fractions of Morris hepatoma 5123tc (h) and rat liver were studied with regard to their relative basal activties of adenylate cyclase and to the comparative responsiveness of this enzyme to glucagon, sodium fluoride, epinephrine, prostaglandin E1, and insulin. The basal adenylate cyclase activities of the hepatoma fractions were found to be similar to those of liver at an adenosine 5'triphosphate concentration of 3.2 mM; if the substrate affinity (Km adenosine 5'-triphosphate) of the tumor enzyme is comparable to that of liver, these findings suggest that the reduced basal cyclic adenosine 3':5'-monophosphate levels found to occur in hepatoma 5123tc (h) probably are not due to a decreased basal rate of formation of this cyclic nucleotide. Glucagon (5.6 muM) significantly stimulated adenylate cyclase in both fractions of hepatoma and livers; however, the responsiveness of the tumor enzyme to this hormone was substantially lower than the responsiveness of liver for both homogenate and plasma membrane preparations; i.e., activities were enhanced 18-fold (relative to the basal activity)for liver homogenate compared with only a 6-fold increase for tumor. With the plasma membrane preparations, glucagon increased the activities 5- and 3.5-fold in liver and hepatoma, respectively. Sodium fluoride (10mM), in contrast to glucagon, increased the adenylate cyclase activity to approximately the same extent (about 10-fold) in the liver and hepatoma preparations. Epinephrine (100 muM) enhanced the liver and hepatoma homogenate activites 3- to 4-fold and the hepatoma plasma membrane activities 2-fold; however, the liver plasma membrane activites were not increased. Prostaglandin E1 (56.6 MUM) significantly increased adenylate cyclase activites of liver and hepatoma homogenates (i.e., 1.5- and 3-fold, respectively) but not of the plasma membrane preparations. Insulin (0.7 muM) did not significantly alter adenylate cyclase activities in any of the preparations.
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PMID:Comparative adenylate cyclase activities in homogenate and plasma membrane fractions of Morris hepatoma 5123tc (h). 16 85


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