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 effects of pH, temperature and guanidine hydrochloride concentration on the structure of ubiquitin, a polypeptide which can activate adenylate cyclase and can mimic thymopoietin induced differentiation of prothymocytes, were monitored using nuclear magnetic resonance spectroscopy. This relatively small polypeptide (molecular weight of 8541) exhibits a remarkable stability towards pH and temperature changes. At 7 M guanidine hydrochloride concentration, the structure of ubiquitin is essentially a random coil.
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PMID:Nuclear magnetic resonance studies of the denaturation of ubiquitin. 2 Jan 53

Retro-orbital tissue membranes have been shown to have adenylate cyclase activity which can be stimulated by thyrotropin and by an exophthalmogenic factor derived from the thyrotropin molecule by partial pepsin digestion. This stimulable activity is maximal after 15 min and is optimal in the presence of 3 mM magnesium and 1.5 mM ATP. Calcium salts are exquisitely inhibitory to the hormonal stimulation; sodium, lithium, and ammonium salts are significantly less inhibitory. Thyrotropin and the exophthalmogenic factor induce similar maximal levels of stimulation but a 4- to 5-fold higher concentration of exophthalmogenic factor is required to achieve this level. Fluoride stimulates adenylate cyclase activity 2- to 3-fold higher than either thyrotropin or the exophthalmogenic factor; thyrotropin, luteinizing hormone, the beta subunit of thyrotropin, and the alpha subunit of thyrotropin have relative activities for stimulation of cyclase activity of 100:2:2 less than 0.5. Several other polypeptide and glycoprotein hormones have no effect. The gamma-globulin from patients with malignant exophthalmos has no significant effect on cyclase activity either alone or in the presence of maximal levels of thyrotropin or the exophthalmogenic factor; this gamma-globulin does, however, stimulate cyclase activity at submaximal hormone levels. Trypsin not only destroys the hormone-stimulable adenylate cyclase activity on retro-orbital tissue plasma membranes, but also destroys it on the 15,000 to 30,000 molecular weight receptor fragment released from the membranes by the tryptic action.
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PMID:Stimulation of adenylate cyclase activity in retro-orbital tissue membranes by thyrotropin and an exophthalmogenic factor derived from thyrotropin. 5 Oct 22

Three different bile acids--deoxycholic acid, chenodeoxycholic acid and ursodeoxycholic acid--were tested for their capacity to stimulate the adenylate cyclase in human colonic mucosa. This enzyme system was found to be sensitive towards vasoactive intestinal polypeptide and prostaglandin E2. These three bile acids were ineffective in activating the human cyclase system over a wide concentration range tested. Concentrations above 1 X 10(-5) mmol/l induced a dose-dependent inhibition of basal enzyme activity. These results suggest that bile-acid induced diarrhoea is not associated with activation of the membrane-bound adenylate cyclase system at least in man.
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PMID:Human colonic adenylate cyclase: effects of bile acids. 10 25

Four-fold increases in cyclic AMP levels were observed 5 to 10 min after rat pancreatic fragments were incubated with 10-7 M secretin or 10-6 M vasoactive intestinal polypeptide (VIP), in addition to 10 mM theophylline. From dose-response curves it appears that, on a molar basis, the potency of secretin was 20 times higher than that of VIP. It is concluded that cyclic AMP is probably the intracellular messenger of both secretin and VIP in centroacinar cells. Pancreozymin, caerulein, and the C-terminal octapeptide of pancreozymin inhibited the production of cyclic AMP observed with secretin of VIP, suggesting that the first three peptides were acting at a binding site different from the agonists, but coupled with the same adenylate cyclase. In acinar cells, secretin was able to exert slight ecbolic effects, and was also able to potentiate the effect of maximal concentrations of pancreozymin, caerulein, or the C-terminal octapeptide of pancreozymin. There was no simple correlation between amylase output and cyclic AMP levels, and copious amylase secretion was elicited even at control levels of cyclic AMP. Glucagon was neither an agonist nor an antagonist of any of the other polypeptides tested.
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PMID:In vitro interactions of gastrointestinal hormones on cyclic adenosine 3':5'-monophosphate levels and amylase output in the rat pancreas. 16 79

Rat liver membrane adenylate cyclase (EC 4.6.1.1) that has been stimulated more than 10-fold by cholera toxin (choleragen) has a 3-fold greater sensitivity to stimulation by glucagon. Choleragen similarly increases the sensitivity of cyclase to other peptide (ACTH, vasoactive intestinal polypeptide) and nonpeptide (catecholamines) hormones in this and other tissues. The rate of 125I-labeled glucagon-membrane dissociation is decreased about 2-fold in toxin-treated liver membranes. Toxin-activated cyclase activity of fat cell membranes is retained upon solubilization with Lubrol PX. Provided 125I-labeled choleragen is first incubated with cells under conditions resulting in enzyme activation, the solubilized cyclase activity migrates with a component of 125I-labeled choleragen on gel filtration chromatography. Agarose derivatives containing the "active" subunit (molecular weight 36,000) of the toxin can specifically adsorb solubilized adenylate cyclase. Toxin-stimulated cyclase can be immunoprecipitated with antitoxin or anti-"active" subunit antibodies. There is a large excess of membrane receptors (ganglioside GM1) which, with the use of choleragenoid, can be shown to be functionally equivalent with respect to cyclase activation. Choleragenoid, an inactive competitive antagonist of toxin binding, can occupy and block a large proportion of toxin receptors without affecting toxin activity. A scheme of toxin action is proposed that involves lateral membrane diffusion of the initially inactive toxin-receptor complex with subsequent direct interaction with and modulation of adenylate cyclase. The basic features of this scheme may be pertinent to the mechanisms by which hormone receptors normally modulate adenylate cyclase.
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PMID:Mechanism of action of cholera toxin and the mobile receptor theory of hormone receptor-adenylate cyclase interactions. 16 20

The kinetics for inactivation of rat liver plasma membrane adenylate cyclase by iodoacetic acid and iodoacetamide has been measured in the presence and absence of glucagon. Glucagon stimulated the rate of iodoacetic acid inhibition by a factor 9f 2.3-fold and iodoacetamide inhibition by 10-fold. These results suggest that interaction of glucagon with its receptor in the membrane resulted in conformational changes which increased either the exposure or nucleophilicity of one or more sulfhydryl groups crucial for adenylate cyclase activity. Membranes were treated with radioactively labeled iodoacetamide or iodoacetic acid in the presence or absence of glucagon and run on 5 and 7.5% sodium dodecylsulfate polyacrylamide gels. These labeling experiments revealed that two membrane components were more extensively labeled in the presence of glucagon. The first component had an apparent molecular weight of 240,000 on sodium dodecyl sulfate gels and stained positive with Coomassie blue and periodate Schiff reagent. This polypeptide accounted for approximately 1.3% of the total membrane protein. The second component had an apparent molecular weight less than 10,000 and could not be correlated directly with a well defined protein band on sodium dodecyl sulfate polyacrylamide gels. The enhancement in labeling of the 240,000 molecular weight component seen in the presence of glucagon agreed very well with that predicted from the kinetics for inhibition of adenylate cyclase activity in the presence and absence of glucagon. This correlation suggests that the component selectively labeled by this technique may be an integral component of the adenylate cyclase system and that hormone-induced conformational changes may be used to selectively label components of the adenylate cyclase system in mammalian membranes.
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PMID:Exploitation of hormone-induced conformational changes to label selectively a component of rat liver plasma membranes. 16 45

Hepatocytes and Kupffer cells were separated from rat liver after prelabeling the Kupffer cells with colloidal iron and perfusion of the liver with digestive enzymes. The activity of several enzymes from Kupffer cells and hepatocytes was compared to validate this method of cell separation. The ratios of hepatocyte to Kupffer cell specific activities of glucose-6-phosphatase, 5'-nucleotidase, adenylate cyclase, and acid phosphatase were 20, 0.39, 0.18, and 0.078, respectively. Adenylate cyclases from hepatocytes and Kupffer cells were stimulated by fluoride ion, GTP, and catecholamines. Hepatocyte adenylate cyclase was also stimulated by glucagon, secretin, vasoactive intestinal polypeptide, and by prostaglandin E1, whereas, the Kupffer cell enzyme was completely insensitive to these hormones. The stimulation of hepatocyte adenylate cyclase by combinations of glucagon plus secretin, or glucagon plus vasoactive intestinal polypeptide, were equivalent to the sum of the individual stimulations. This suggests that the hepatocyte has specific receptors for glucagon and for vasoactive intestinal polypeptide and secretin. Prostaglandin E1 stimulation of hepatocyte adenylate cyclase was not additive to the stimulation caused by polypeptide hormones or catecholamines, nor did prostaglandin E1 decrease stimulation caused by these hormones. Although prostaglandin-sensitive adenylate cyclase was recovered with hepatocytes, 40 to 50% of the total liver prostaglandin-sensitive activity was recovered in a fraction of cell debris mixed with small cells which did not phagocytize colloidal iron.
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PMID:Stimulation of adenylate cyclase from isolated hepatocytes and Kupffer cells. 17 Dec 69

The influence of Vibrio cholerae enterotoxin (choleragen) on the response of adenylate cyclase to hormones and GTP, and on the binding of 125I-labeled glucagon to membranes, has been examined primarily in rat adipocytes, but also in guinea pig ileal mucosa and rat liver. Incubation of fat cells with choleragen converts adenylate cyclase to a GTP-responsive state; (-)-isoproterenol has a similar effect when added directly to membranes. Choleragen also increases by two- to fivefold the apparent affinity of (-)-isoproterenol, ACTH, glucagon, and vasoactive intestinal polypeptide for the activation of adenylate cyclase. This effect on vasoactive intestinal polypeptide action is also seen with the enzyme of guinea pig ileal mucosa; the toxin-induced sensitivity to VIP may be relevant in the pathogenesis of cholera diarrhea. The apparent affinity of binding of 125I-labeled glucagon is increased about 1.5- to twofold in choleragen-treated liver and fat cell membranes. The effects of choleragen on the response of adenylate cyclase to hormones are independent of protein synthesis, and they are not simply a consequence to protracted stimulation of the enzyme in vivo or during preparation of the membranes. Activation of cyclase in rat erythrocytes by choleragen is not impaired by agents which disrupt microtubules or microfilaments, and it is still observed in cultured fibroblasts after completely suppressing protein synthesis with diphtheria toxin. Choleragen does not interact directly with hormone receptor sites. Simple occupation of the choleragen binding sites with the analog, choleragenoid, does not lead to any of the biological effects of the toxin.
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PMID:Mechanism of activation of adenylate cyclase by Vibrio cholerae enterotoxin. Relations to the mode of activation by hormones. 17 36

Glycerol release from epididymal fat fragments of young adult (3-month old) ob/ob mice was three times lower than normal, on a tissue weight basis. Dose-response curves in response to isoproterenol and ACTH-(1--24) indicated that the capacity of the lipolytic process was reduced. However, the sensitivity to both hormones was normal, i.e. greater for ACTH than for isoproterenol. The burst of cyclic AMP observed at 7 minutes was affected even more than the lipolytic capacity in adipose tissue from obese mice. This was already observed in 1-month old animals, i.e. at a time when total body weight was still normal. It is concluded that the adenylate cyclase system is defective in adipose tissue of ob/ob mice. Besides, glucagon, vasoactive intestinal polypeptide, and secretin failed to stimulate glycerol release and cyclic AMP accumulation in both ob/ob, ob+/ob+, and HA-ICR mice, suggesting that mouse adipose tissue does not possess receptors for this group of hormones.
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PMID:Lipolysis and cyclic AMP levels in epididymal adipose tissue of obese-hyperglycaemic mice. 20 30

The effects of various polypeptide hormones known to inhibit gastric acid secretion were tested on the adenylate cyclase system in human gastric and duodenal mucosal homogenates. Glucagon and secretin failed to stimulate the enzyme system in the stomach. The latter hormone produced a small but significant activation of the duodenal cyclase. The vasoactive intestinal polypeptide (VIP), however, induced a dose-dependent increase of enzyme activity throughout the stomach and the duodenum. Maximal effects (1.8 to 3.0-fold increase) were observed at a VIP-concentration of about 10 microgram per ml. Because the entire physiological role of VIP in gastric function has not been defined, ipt cannot be discerned whether the VIP-stimulated adenylate cyclase is linked to inhibition of gastric acid secretion or to another as yet unrecognized effect of this hormone in human gastric function.
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PMID:Activation of human adenylate cyclase in the upper gastrointestinal tract by vasoactive intestinal polypeptide. 20 35


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