Showing papers on "Cyclase published in 1969"
TL;DR: It was concluded that ACTH and fluoride ion activate the same enzyme and alter the same kinetic parameter involved in activation, but do so by different means.
408 citations
TL;DR: Guanyl cyclase, an enzyme catalyzing the formation of guanosine 3',5'-monophosphate from Guanosine triphosphate, has been identified in a variety of animal tissues and preliminary attempts to purify the enzyme by conventional techniques have yielded a purification of about 20-fold.
372 citations
TL;DR: It was concluded that the hormones act at discrete hormone-specific sites (or receptors) that affect the activity of a single adenyladenyl cyclase in fat cells.
335 citations
TL;DR: An enzyme system which catalyzed the formation of cyclic GMP from GTP was demonstrated in small intestine, and this enzyme required Mn++ for maximal activity and was inhibited by ATP, suggesting a rapid turnover of the nucleotide in this tissue.
253 citations
TL;DR: It is concluded that secretin activates adenyl cyclase in fat cells via a receptor that is distinct from the receptors for glucagon and the other lipolytic hormones.
232 citations
TL;DR: Adenyl cyclase in calvaria was not sensitive to a variety of hormones known to stimulate this enzyme in other tissues, and these observations provide the basis for the concept that a single type of interaction between hormone and enzyme bound to...
Abstract: The effect of parathyroid hormone on adenyl cyclase from fetal rat calvaria was tested. Adenyl cyclase was assayed in particulate fractions from this tissue by measuring conversion of ATP-α-32P to 3′,5′-AM32P. Parathyroid hormone caused rapid stimulation of enzyme activity; the degree of stimulation was related to the log of hormone concentration. Adenyl cyclase in calvaria was not sensitive to a variety of hormones known to stimulate this enzyme in other tissues. The enzyme was sensitive to parathyroid hormone in skeletal and renal cortical tissue but not in heart, brain, spleen, thyroid, adrenal, or fat cells. Parathyroid hormone and sodium fluoride also stimulated theenzyme in calcified bone from adult rats. Neither parathyroid hormone nor thyrocalcitonin affected the activity of cyclic nucleotide phosphodiesterase in skeletal tissue, nor did thyrocalci tonin affect adenyl cyclase. These observations provide the basis for the concept that a single type of interaction between hormone and enzyme bound to...
218 citations
TL;DR: Findings are consistent with the hypotheses that the positive inotropic effects of epinephrine and glucagon may occur as a result of an augmentation of the sarcotubular calcium pool(s) and this effect is mediated, at least in part, by an elevation of cyclic 39, 59-AMP levels produced by activation of an adenyl cyclase localized to the sarcoplasmic reticulum.
Abstract: The mechanisms by which the catecholamines and glucagon increase myocardial contractility were investigated by studying the effects of cyclic 39, 59-AMP, epinephrine, and glucagon on calcium accumulation by a microsomal fraction of canine myocardium thought to represent sarcoplasmic reticulum, and by assaying the microsomal fraction for adenyl cyclase activity. Each agent produced a concentration-dependent increase in calcium accumulation. Moreover, adenyl cyclase, an enzyme activated by epinephrine and glucagon and responsible for the production of cyclic 39, 59-AMP, was present in the microsomal fraction. Its specific activity and responsiveness to epinephrine and glucagon were similar to that previously found in sarcolemmic fractions. The beta-receptor blocking agent propranolol abolished the activation of adenyl cyclase and increase in microsomal calcium accumulation produced by epinephrine, but was without effect when these same changes were produced by glucagon. These findings are consistent with the hypotheses that: (1) the positive inotropic effects of epinephrine and glucagon may occur as a result of an augmentation of the sarcotubular calcium pool(s); and (2) this effect is mediated, at least in part, by an elevation of cyclic 39, 59-AMP levels produced by activation of an adenyl cyclase localized to the sarcoplasmic reticulum.
194 citations
TL;DR: The present review has been placed on carbohydrate metabolism, but lipid metabolism has also been discussed to some extent, and the chief role of cyclic AMP in several tissues seems to be to facilitate or promote the mobilization of glucose and fatty acid reserves.
Abstract: Cyclic AMP plays an important role in the regulation of metabolism generally. Emphasis in the present review has been placed on carbohydrate metabolism, but lipid metabolism has also been discussed to some extent. The chief role of cyclic AMP in several tissues seems to be to facilitate or promote the mobilization of glucose and fatty acid reserves. In the liver, glucagon and the catecholamines cause an increase in the intracellular level of cyclic AMPby stimulating adenyl cyclase. This increase in the level of .cyclic AMP leads to a net increase in hepatic glucose production by at least three mechanisms: stimulation of phosphorylase activation, suppression of glycogen synthetase activity, and stimulation of gluconeogenesis. The catecholamines also stimulate adenyl cyclase in muscle and adipose tissue. Among the principal effects of cyclic AMP in these tissues are glycogenolysis in muscle and lipolysis in adipose tissue. Another role of cyclic AMP is to enhance or promote the release of insulin from pancreatic beta cells. Insulin then travels to the liver and adipose tissue to suppress the accumulation of cyclic AMP, and may also antagonize the action of cyclic AMP in muscle. Cyclic AMP is thus seen to mediate the actions of several catabolic hormones as well as promote the release of an anabolic hormone which acts in part by opposing cyclic AMP. Since cyclic AMP is involved in the release as well as several of the actions of insulin, the possible role of cyclic AMP in diabetes has been discussed. Human diabetes mellitus is recognized as the result of a basic genetic defect, the nature of which is undefined. One line of evidence implicates basement membrane thickening as an early event in the patho genesis of diabetes. Further study of the formation and breakdown of the basement membrane may therefore lead to a better understanding of the genetic defect. Whether or not cyclic AMP plays a regulatory role in basement membrane synthesis is presently unknown. Another defect recognizable in prediabetics is faulty insulin release in response to glucose infusion. This could be secondary to basement membrane thickening, but there is also evidence that the cyclic AMP mechanism may be defective. At another level, the role of cyclic AMP is more obvious: insulin deficiency leaves unopposed the actions of hormones which stimulate the production of cyclic AMP, thereby contributing to the glucose plethora and ketosis so often seen in the later stages of the disease.
193 citations
TL;DR: It is concluded that cyclic AMP is necessary for the normal utilization of a number of carbon sources by E. coli, because it is required for the synthesis of enzymes involved in their metabolism.
190 citations
TL;DR: Removal of calcium by EDTA appear to increase PGE stimulation of adenyl cyclase without altering NaF stimulation, confirming the hypothesis that calcium plays a role in regulating the sentivity of cell membranes to hormones or the hormone-like prostaglandins.
184 citations
TL;DR: The failure of DL-propranolol to block the glucagon-mediated activation of adenyl cyclase suggests that there are at least two receptor sites in myocardial tissue responsible for the activation ofadenylcyclase, one responsive to glucagon and one to norepinephrine.
Abstract: The purpose of this investigation was to determine the direct effects of glucagon on adenyl cyclase activity in cat and human heart particles and to elucidate the role of the beta receptor in any glucagon-mediated activation of adenyl cyclase. At the peak of its dose-response curve, crystalline glucagon increased the conversion of AT32P to cyclic 3', 5'-AM32P in particulate fractions of both cat and human heart homogenates by approximately 70%. The activation of adenyl cyclase was dose-related over a concentration ranging from 1 x 10-7M to 1 x 10-5M. Half maximal activity was observed at 8 x 10-7M. DL-propranolol, 1 x 10-5M, did not block the activation of adenyl cyclase produced by glucagon, 1 x 10-6M or 1 x 10-5M. However, the same concentration of propranolol blocked adenyl cyclase activation induced by norepinephrine, 1 x 10-6M and 1 x 10-5M. Combined maximal doses of glucagon and norepinephrine did not produce additive effects on the activation of adenyl cyclase. The failure of DL-propranolol to bloc...
TL;DR: A bioassay for parathyroid hormone in vitro was developed based upon the activation of adenyl cyclase from the renal cortex of the rat and showed appropriate increments in potency for hormone preparations at consecutive stages of purification.
Abstract: A bioassay for parathyroid hormone in vitro was developed based upon the activation of adenyl cyclase from the renal cortex of the rat. Preparation of the enzyme in 0.05M Tris-HCl, pH 7.4, containing 10% v/v dimethylsulfoxide allowed storage in liquid nitrogen for periods in excess of 30 days without significant loss of sensitivity to parathyroid hormone or fluoride. The assay was sensitive to as little as 0.14 USP U of parathyroid hormone, and showed a log-linear dose response over the range of 0.14– 1.13 USP U of hormone. The average index of precision in a series of 23 assays was 0.083. Theassay was highly specific for parathyroid hormone and showed appropriate increments in potency for hormone preparations at consecutive stages of purification. Results with the adenyl cyclase method in vitro were similar to those obtained with a standard bioassay in vivo. There was no significant interference from other hormones and proteins, including nonhormonal contaminants found in crude parathyroid extracts. The ...
TL;DR: Thyroxine is capable of activating myocardial adenyl cyclase in vitro and this effect is not mediated by the beta adrenergic receptor, compatible with the hypothesis that the cardiac manifestations of the hyperthyroid state may, in part, be caused by the direct activation of myocardia adenol cyclase by thyroid hormone.
Abstract: The mechanism responsible for the hyperdynamic circulatory state in hyperthyroidism has not been defined. Although certain cardiac manifestations resemble those caused by excessive adrenergic stimulation, recent evidence suggests that thyroid hormone exerts an effect on the heart that is independent of the adrenergic system. Since the inotropic and chronotropic effects of norepinephrine appear to be mediated by activation of adenyl cyclase, the possibility that thyroxine and triiodothyronine are also capable of activating adenyl cyclase was examined in the particulate fraction of cat heart homogenates.
L-thyroxine and L-triiodothyronine increased the conversion of adenosine triphosphate-32P (ATP-32P) to cyclic 3′,5′-adenosine monophosphate-32P (3′,5′-AMP-32P) by 60 and 45% respectively (P < 0.01). A variety of compounds structurally related to the thyroid hormones, but devoid of thyromimetic activity did not activate adenyl cyclase: these included 3,5-diiodo-L-thyronine, L-thyronine, 3,5-diiodotyrosine, monoiodotyrosine, and tyrosine. D-thyroxine activated adenyl cyclase and half maximal activity was identical to that of the L-isomer. Although the beta adrenergic blocking agent propranolol abolished norepinephrine-induced activation of adenyl cyclase, it failed to alter activation caused by thyroxine. When maximal concentrations of L-thyroxine (5 × 10-6 moles/liter) and norepinephrine (5 × 10-5 moles/liter) were incubated together, an additive effect on cyclic 3′,5′-AMP production resulted.
This investigation demonstrates: (a) thyroid hormone is capable of activating myocardial adenyl cyclase in vitro and (b) this effect is not mediated by the beta adrenergic receptor. Moreover, the additive effects of norepinephrine and thyroxine suggest that at least two separate adenyl cyclase systems are present in the heart, one responsive to norepinephrine, the other to thyroid hormone.
These findings are compatible with the hypothesis that the cardiac manifestations of the hyperthyroid state may, in part, be caused by the direct activation of myocardial adenyl cyclase by thyroid hormone.
TL;DR: The plasma membrane of hepatic parenchymal cells contains an adenyl cyclase system that is stimulated by glucagon, and these findings support the concept that glucagon exerts its regulatory action in the liver by stimulating adenYL cyclase activity in the plasma membrane.
Abstract: The plasma membrane of hepatic parenchymal cells contains an adenyl cyclase system that is stimulated by glucagon. Adrenocorticotropin and epinephrine do not stimulate this adenyl cyclase, and very little cyclic phospho-diesterase activity is present in the membrane. These findings support the concept that glucagon exerts its regulatory action in the liver by stimulating adenyl cyclase activity in the plasma membrane.
TL;DR: Thyroid-stimulating hormone (TSH) rapidly increased cyclic adenosine 3',5'-monophosphate (cyclic AMP) concentration in canine thyroid slices while luteinizing hormone, adrenocorticotropic hormone, and prolactin were ineffective and TSH stimulation could still be obtained in the presence of 10-2 m NaF.
TL;DR: It is shown that prostaglandin PGE1 is a potent inhibitor of platelet clumping and increases the level of cyclic AMP in adipose tissue but in some circumstances may lower its concentration in isolated fat cells.
Abstract: ALTERATIONS in the intracellular concentration of cyclic 3′,5′-AMP have been implicated in the action of many hormones and pharmacological agents in a variety of tissues1. In many cases, drugs, the action of which in liver, myocardium, adrenal and other tissues has been attributed to their effects on cyclic AMP concentrations, are known to influence aggregation of blood platelets, for example, platelet aggregation is inhibited by methyl xanthines2 and reserpine3, which inhibit cyclic nucleotide phosphodiesterase4,5, and is augmented by epinephrine6, which stimulates adenyl cyclase in liver, fat cells and myocardium7. 5-Hydroxytryptamine induces platelet aggregation8; it stimulates adenyl cyclase in the liver fluke9. Prostaglandin PGE1 is a potent inhibitor of platelet clumping10; it increases the level of cyclic AMP in adipose tissue11 but in some circumstances may lower its concentration in isolated fat cells1.
TL;DR: The purified adenyl cyclase fraction did not contain cyclic 3′,5′-nucleotide phosphodiesterase activity, exhibited optimal activity at pH 8.0, and was inhibited by Zn 2+ or Ca 2+ .
TL;DR: ACTH sensitivity of adenyl cyclase in mitochondrial and microsomal fractions from bovine adrenal cortex and in ghosts from rat fat cells can be abolished by the Ca complexing agent EGTA and restored by addition of Ca, which may regulate 3′,5′-AMP formation both in the absence and presence of hormones.
TL;DR: An adrenocorticotropic hormone (ACTH)-sensitive, steroid-producing mouse adrenal tumor was homogenized and fractionated by differential centrifugation and adenyl cyclase activity that was stimulated by ACTH and by fluoride was purified 10- to 20-fold and localized to particulate fractions.
TL;DR: The results show that in the membrane of the fat cell a single catalytic unit of adenyl cyclase is coupled to distinctive selectivity sites for three lipolytic hormones.
Abstract: A large number of hormones, of diverse molecular structure, evoke characteristic responses in target cells via the intermediary 3′,5′-AMP, the specificity of hormone action upon cell type being achieved by selective stimulation of adenyl cyclase. In the fat cells of rat adipose tissue, adenyl cyclase is stimulated by a number of hormones of disparate molecular structure, posing the question whether this cell type posesses multiple cyclase systems with distinctive specificities for individual hormones, or a single cyclase with broad specificity to a variety of hormones.
Studies of the stimulatory effects of adenocorticotropin, glucagon, and epinephrine upon the adenyl cyclase of the rat fat cell “ghosts” (plasma membrane sacs) have shown that distinctive selectivity sites for each of these hormones can be differentiated. The β-adrenergic blocking agent Ko 592 abolished the stimulatory effect of epinephrine without influencing adenocorticotropin or glucagon; Ca was required for adenocorticotropin action, but not for glucagon or epinephrine. Dose-response curves show that the affinity of hormones to the cyclase system was in the order: glucagon > adenocorticotropin ≫ epinephrine; the magnitude of cyclase activation by maximal doses of hormones had a reversed order. Combinations of maximal doses of hormones failed to produce additive stimulation. The results show that in the membrane of the fat cell a single catalytic unit of adenyl cyclase is coupled to distinctive selectivity sites for three lipolytic hormones.
TL;DR: Results of the study suggest that adenosine-3',5' monophosphate may be important in the regulation of platelet adhesiveness.
TL;DR: An assay of adenyl cyclase in the fat cell ghost preparation is described that permits measurement of enzyme in the presence of 10,000-fold excess of ATPase activity.
TL;DR: Observations indicated that these hormones increased heart adenyl cyclase activity by different mechanisms and could be blocked by beta-adrenergic blocking agents.
TL;DR: The increased adenyl cyclase and cyAMP produced by hypothalamic extract was associated with greater luteinizing hormone release from anterior pituitary in vitro.
Abstract: Hypothalamic extract, containing the releasing factors for anterior pituitary hormones, within minutes stimulated adenyl cyclase activity and adenosine 3′:5′-cyclic phosphate (cyAMP) concentrations in rat anterior pituitary in vitro. Cerebral cortical extract was ineffective and hypothalamic extract had no effect on these parameters in posterior pituitary or thyroid. Prostaglandin E1 also increased adenyl cyclase activity and cyAMP levels in anterior pituitary tissue. Although NaF augmented adenyl cyclase activity, it did not elevate cyAMP. Epinephrine, norepinephrine, histamine, serotonin, dopamine, and vasopressin did not increase either adenyl cyclase or cyAMP. The increased adenyl cyclase and cyAMP produced by hypothalamic extract was associated with greater luteinizing hormone release from anterior pituitary in vitro.
TL;DR: Evidence is provided in support of the hypothesis that the physiologic and biochemical effects of interstitial cell stimulating hormone and follicle stimulating hormone in testis and probably in ovary are mediated through adenosine 3′,5′-monophosphate.
TL;DR: The results indicate that epinephrine binds to a receptor protein rather than interacting directly with the enzyme adenyl cyclase, which is shown to be specifically localized in the plasma membrane of rat liver.
TL;DR: This report represents the first demonstration of adenyl cyclase in cardiac sarcoplasmic reticulum and the lack of any glutamic dehydrogenase activity suggests that no contaminating mitochondrial fragments are present.
TL;DR: The hypothesis that many effects of thyrotropin on thyroid tissue are, to a large extent if perhaps not exclusively, secondary to the activation of thyroid adenyl cyclase by this hormone is supported.
Abstract: Under appropriate conditions, thyrotropin stimulated the binding of [131I]iodide to proteins in sheep, calf and dog thyroid slices. In dog thyroid slices, thyrotropin, dibutyl cyclic 3′:5′-adenosine monophosphate, and cyclic 3′:5′-AMP in the presence of caffeine, stimulated glucose oxidation at C-1, [131I]iodide binding to proteins and intracellular colloid droplet formation; no such effect was obtained with butyrate, 5′-AMP, ADP, ATP or caffeine. The stimulation of [131I]iodide binding to proteins and of glucose oxidation at C-1 by low concentrations of thyrotropin (0.5 mU/ml) was enhanced in the presence of caffeine. These data support the hypothesis that many effects of thyrotropin on thyroid tissue are, to a large extent if perhaps not exclusively, secondary to the activation of thyroid adenyl cyclase by this hormone. Fluoride, which activates adenyl cyclase in acellular systems, mimicked the effects of thyrotropin on glucose C-1 oxidation and on [131I]iodide binding to proteins. Prostaglandin E1, which in some tissues increases the intracellular levels of cyclic 3′:5′-AMP, also stimulated these metabolic steps. No effect of fluoride and prostaglandin E1 on intracellular colloid droplet formation was observed.
TL;DR: A soluble cyclase is found using for assay radioactively marked ATP as precursor and has a Mg(++) requirement and is inhibited by fluoride and inorganic pyrophosphate.
Abstract: We have found a soluble cyclase, using for assay radioactively marked ATP as precursor. The reaction product was isolated by thin-layer chromatography and identified by specific degradation. After homogenization, part of the activity remained in the particulate fraction but could be easily extracted. The cyclase was concentrated 100-fold by conventional methods. The enzyme has a Mg++ requirement and is inhibited by fluoride and inorganic pyrophosphate.
Journal Article•
TL;DR: The results suggest that sympathetic nerve activity may have a chronic as well as an acute influence on the catalytic capacity of the pineal adenyl cyclase system.
Abstract: Adenyl cyclase activity of rat pineal gland homogenates was determined by measuring the rate of conversion of adenosine triphosphate-8-C 14 to radioactive cyclic 3’,5’-adenosine monophosphate. Norepinephrine and sodium fiuoride, which act at different sites on the pineal adenyl cyclase system, increased enzyme activity. Exposure of rats to continuous light for several days potentiated the norepinephrine-induced activation of pineal adenyl cyclase. Environmental lighting also enhanced the response of the pineal enzyme to sodium fluoride, indicating that light produced a general alteration of the enzyme system rather than a change at a site specific for the catecholamine. The light-induced increase in the activation of adenyl cyclase by norepinephrine was antagonized by removal of the superior cervical ganglia, a procedure which denervates the pineal gland. Effects similar to those produced by light exposure were seen in pineal glands chronically denervated (4-10 weeks) by bilateral superior cervical ganglionectomy; that is, the stimulation of adenyl cyclase elicited by both norepinephrine and sodium fluoride was increased. In addition, the activation of adenyl cyclase by maximal as well as by submaximal concentrations of the catecholamine was potentiated by chronic denervation, indicating that there was more enzyme rather than a greater affinity of adenyl cyclase for norepinephrine. These results suggest that sympathetic nerve activity may have a chronic as well as an acute influence on the catalytic capacity of the pineal adenyl cyclase system. Received for publication August 15, 1968.