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 aim of this study was to determine whether steroidogenesis occurs in human immature oocytes aspirated from follicles during gynecologic laparotomy. delta 5-3 beta-Hydroxysteroid dehydrogenase (delta 5-3 beta-HSD) and 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) activities were detected by Dickmann and Dey's reaction medium consisting of 1.8 mg substrate (pregnenolone or 17 beta-estradiol [E2]), 4 mg nicotinamide-adenine dinucleotide, 2 mg nitro-blue tetrazolium, 10 ml 0.1 M phosphate buffer. The activity of adenylate cyclase was examined by ultrastructural-cytochemical study using 5'-adenylyl-imidodiphosphate (AMP-PNP) as a substrate in Vorbrodt's medium of 0.005 M AMP-PNP, 0.001 M MgCl2, 0.02 M SrCl2, 0.01 M NaF, 0.002 M theophylline, 0.01 M Tris-HCl. Furthermore, in indirect immunofluorescence study, the presence of endogenous progesterone and E2 and the activity of delta 5-3 beta-HSD were demonstrated. The results suggest that steroidogenesis, through the adenylate cyclase-cyclic adenosine 3':5'-monophosphate system, in human oocytes may play some important role in oocyte maturation, fertilization, and early embryonic development. The implication of steroid-producing activities of the human oocytes for cytoplasmic maturation is discussed.
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PMID:Cytochemical study of steroid-producing activities of human oocytes. 630 92

The actions of cholera toxin (i.e., activation of adenylate cyclase and ADP-ribosylation of a guanine nucleotide binding protein in purified membranes from rat liver) were GTP dependent. Neither of these actions of cholera toxin was reproduced with GDP. Simultaneous addition of ATP and MgCl2 along with GDP allowed cholera toxin to exert these actions. The role of GDP in adenylate cyclase regulation was discussed.
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PMID:GDP does not support activation of adenylate cyclase nor ADP-ribosylation of a guanine nucleotide binding protein by cholera toxin. 630 53

beta-Adrenergic receptors from turkey erythrocyte membranes have been purified 1000-4000-fold using alprenolol-Sepharose affinity chromatography. Addition of deoxycholate solubilized egg phosphatidylcholine to the beta-adrenergic receptor, that is 5-10% pure and in 0.1% digitonin, followed by Sephadex G-50 gel filtration in buffers containing 30 mM MgCl2 results in 65-70% of the receptor being incorporated into phospholipid vesicles. The beta-adrenergic receptor as detected by photoaffinity labeling using [125I]azidobenzylpindolol in membranes and after alprenolol-Sepharose chromatography is a Mr = 40,000 peptide. Addition of deoxycholate extracts of human erythrocyte membranes, which contain the guanine nucleotide stimulatory regulatory protein of adenylate cyclase (Ns) but not beta-adrenergic receptor, were used to reconstitute a guanine nucleotide-mediated change in agonist affinity for the receptor. These results demonstrate that the alprenolol-Sepharose affinity purified beta-adrenergic receptor is functional in both ligand binding and coupling to Ns. The procedure is rapid, efficient and should be generally applicable to beta-adrenergic receptor and Ns from several different membrane systems.
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PMID:Rapid vesicle reconstitution of alprenolol-Sepharose-purified beta 1-adrenergic receptors. Interaction of the purified receptor with N. 631 81

[12-3H]Forskolin (27 Ci/mmol) has been used to study binding sites in rat brain tissue by using both centrifugation and filtration assays. The binding isotherm measured in the presence of 5 mM MgCl2 by using the centrifugation assay is described best by a two-site model: Kd1 = 15 nM, Bmax1 (maximal binding) = 270 fmol/mg of protein; Kd2 = 1.1 microM; Bmax2 = 4.2 pmol/mg of protein. Only the high-affinity binding sites are detected when the binding is determined by using a filtration assay; Kd = 26 nM, Bmax = 400 fmol/mg of protein. Analogs of forskolin that do not activate adenylate cyclase (EC 4.6.1.1) do not compete effectively for [3H]forskolin binding sites. Analogs of forskolin that are less potent than forskolin in activating adenylate cyclase are also less potent in competing for forskolin binding sites. The presence of 5 mM MgCl2 or MnCl2 was found to enhance binding. In the presence of 1 mM EDTA the amount of high-affinity binding is reduced to 110 fmol/mg of protein with no change in Kd. There is no effect of CaCl2 (20 mM) or NaCl (100 mM) on the binding. No high-affinity binding can be detected in membranes from ram sperm, which contains an adenylate cyclase that is not activated by forskolin. It is proposed that the high-affinity binding sites for forskolin are associated with the activated complex of catalytic subunit and stimulatory guanine nucleotide binding protein.
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PMID:Binding of [3H]forskolin to rat brain membranes. 643 43

Washed membranes isolated from rat cerebral cortex (gray matter) showed the presence of EGTA-inhibitable and EGTA-insensitive forms of adenylate cyclase activity. The former activity was stimulated by low concentrations (microM) of various divalent cations (Mn2+, Ca2+, Co2+ and Sr2+) assayed with MgATP2- and MgCl2. At higher concentrations (mM), only Mn2+ stimulated this enzyme whereas Ca2+, Co2+ and Sr2+ were inhibitory. Alamethicin markedly (up to 30-fold) increased the activity of EGTA-inhibitable form and only moderately of EGTA-insensitive form of the enzyme. The increased activity due to alamethicin does not result from solubilization of the enzyme from membranes. Our results suggest the presence of two distinct metal binding sites--one of high (Site I) and other of low (Site II) affinity. Divalent metals via interacting with these produce divergent effects on the enzyme. Site I appears to be located in the hydrophobic region of catalytic unit of the enzyme or of membrane-associated calmodulin. The likely significance of these results is briefly presented.
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PMID:Interaction of EGTA with a hydrophobic region inhibits particulate adenylate cyclase from rat cerebral cortex: a study of an EGTA-inhibitable enzyme by using alamethicin. 644 Aug 18

Pregnant rats were fed diets with an Mg2+ content of 40, 12, 6 and 3 mmol/kg from day 10-19 of pregnancy. There was a linear correlation of non-protein bound Mg2+ between foetal and maternal serum, between amniotic fluid and maternal serum, and between foetal serum and amniotic fluid, the ratios being 2.7, 2.0 and 1.3 respectively, indicating active transport of Mg2+ up to a constant concentration gradient by the placenta. In hearts, increases of Na+ and Ca2+, and decreases of Mg2+ and K+ were observed only in the group receiving the lowest Mg2+ supply. After i.v. injection of MgCl2 to pregnant rats, Mg2+ was slowly transported from maternal to foetal serum and more slowly into the amniotic fluid. The effect of isoproterenol on cardiac electrolyte content in pregnant rats was less than in non-pregnant rats, and the effect of isoproterenol in foetal rats was smaller than in maternal rats. These results are explained by inactivation of isoproterenol in the placenta, by the small diaplacental transport of isoproterenol and by a smaller isoproterenol-stimulation of foetal cardiac adenylate cyclase.
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PMID:Foetal and maternal magnesium metabolism: effect of magnesium deficiency and isoproterenol. 666 39

Na+ has been implicated as a requirement for the inhibition of adenylate cyclase by hormones and neurotransmitters. This study examines effects of salt concentration on neuroblastoma plasma membranes that occur in the absence of an inhibitory hormone. The adenylate cyclase response to stimulatory agonists (GTP plus PGE1 (3), PGI2 or PGE2) was influenced by NaCl. As the [NaCl] increased to 150 mM, an increase in maximal activity and a decrease in apparent affinity was observed. At concentrations above 150 mM, NaCl decreased prostaglandin affinity and progressively decreased maximal activation. The GTP requirement was not altered by 30 or 150 mM NaCl in the presence of PGE1 or PGI2. The rate of Gpp(NH)p stimulated activity increased as the [NaCl] was increased in the assay. This increased rate was conserved when membranes activated in the presence of Gpp(NH)p and NaCl were reassayed in the absence of guanine nucleotide or salt. The salt evoked rate increase was proportionally greater at submaximal MgCl2 concentrations. The concentration requirement for Mg2+ was reduced by salt for adenylate cyclase in the presence of GTP or Gpp(NH)p. However, the enzyme stimulated by hormone exhibited a Mg2+ requirement that was low in the absence of salt and could not be further reduced by increased [NaCl]. Alternative monovalent cations (150 mM Li+, K+, Cs+, but not choline or tetramethylammonium) and anions (SO4=) substituted for NaCl. The observed effects were reversible upon washing the membranes and neither ouabain nor tetrodotoxin altered the response. These effects may result from a conformational alteration of a protein particularly sensitive to neutral salts in the assay.
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PMID:Effects of NaCl concentration on adenylate cyclase regulation by prostaglandins and guanine nucleotides. 675 90

A method of measuring the biological activity of parathyroid hormone (PTH) in human serum that depends on the activation of its natural target enzyme, human renal cortical adenylate cyclase, is described. Optimal sensitivity ranging in different assays from 14 to 20 pg 1-34 hPTH/ml was achieved in the presence of the GTP-analogue GppNHp (10 mumol/L), 5 mmol/L MgCl2 and 1.25 mmol/L EGTA. Basal and stimulated cAMP production was reproducible within assays (c.v. below 7%, S.E.M., n = 3) and between assays (c.v. 5 to 14%, S.E.M., n = 4). The recovery of 1-34 hPTH added to individual test sera averaged 94%. The specificity of the method was established as follows: 1.) Other tested hormones, at 100 ng/ml, were ineffective; 2.) In the majority of peripheral sera from patients with hyperfunctioning parathyroid glands elevated bio-activity was detected; 3.) The circulating bio-activity fell rapidly after removal of parathyroid adenomata; 4.) Treatment with antisera for hPTH reduced the bio-activity; 5.) A PTH-antagonist inhibited the bio-activity.
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PMID:A homologous biological probe for parathyroid hormone in human serum. 685 27

The wide range of values reported for activity of adenylate cyclase (AC) in human skeletal muscle prompted re-evaluation of conditions used for homogenization and assay. Adenylate cyclase activity in the same normal muscle differed with different techniques of homogenization. In pH 7.5 isotonic Tris buffer, basal and catecholamine-activated activities declined rapidly in homogenates kept at 4 degrees C. Loss of basal activity was prevented by addition of a chelator of divalent cations. Loss of response to isoproterenol was prevented by addition of guanylnucleotides. Enzyme activity was maximal at 37 degrees C and pH 7.6. Enzyme activity was lower when theophylline was used to prevent degradation of labelled 3',5' cyclic adenosine monophosphate (cyclic AMP) than when unlabelled cyclic AMP was used to this purpose. Basal activity increased with increased MgCl2 concentration up to 50 mmol/l, but isoproterenol-activated activity was maximal at 4 mmol/l MgCl2. AC was inhibited by exogenous adenosine, but addition of adenosine deaminase to the assay mixture did not increase AC activity. Based upon these observations, standardized procedures of homogenization and assay were devised and used to measure AC activity in muscles of boys with Duchenne muscular dystrophy: basal and isoproterenol-stimulated activities were abnormally low.
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PMID:Assay of adenylate cyclase in homogenates of control and Duchenne human skeletal muscle. 722 46

We investigated the influence of Mg2+ and Mn2+ on the effects of adenosine and some derivatives on basal adenylate cyclase activity in rat fat cell membranes as well as on enzyme activity stimulated by isoprenaline or sodium fluoride. Adenosine and derivatives modified in the ribose function were inhibitory, irrespective of the stimulant used, both in the presence of MgCl2 or MnCl2. Inhibition of basal and sodium fluoride stimulated adenylate cyclase activity was more pronounced in the presence of MnCl2 than in the presence of MgCl2. N6-substituted adenosine analogs proved to be inhibitory in the presence of 5 mM MgCl2, but in the presence of 1 mM MnCl2 the fluoride stimulated adenylate cyclase activity was potentiated, while basal and isoprenaline stimulated activity were not significantly inhibited. These effects of adenosine and derivatives could not be blocked by theophylline with or without guanyl nucleotides. The potentiating effect of N6-substituted adenosine derivatives on sodium fluoride activated adenylate cyclase is dependent on the structure of the N6-substituent and consists of an enhancement of Vmax in combination with a small decrease of the Km for MnATP2-, indicative of an allosteric effect on adenylate cyclase. No potentiation by N6-phenylisopropyladenosine of sodium fluoride stimulated cyclase was found on digitonin solubilized cyclase, while the inhibitory effect of adenosine was retained. The relevance of these findings is discussed in connection with the current hypothesis concerning the presence of two adenosine-sensitive sites on rat fat cell membranes.
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PMID:Effects of adenosine and adenosine-analogs on adenylate cyclase activity in the rat adipocyte plasma membrane: comparison of the properties of the enzyme with Mn2+ and Mg2+ as divalent cations. 731 71


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