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)

Choleragen and its A protomer catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide. NADase activity was inhibited by gangliosides GM1 (galactosyl-N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide), GM2 (N-acetylgalactosaminyl-[N-acetylneuraminyl]-galactosylglucosylceramide), GM3 (N-acetylneuraminyl-galactosylglucosylceramide), and GD1a (N-acetylneuraminylgalactosyl-N-acetylgalactosaminyl-E1N-acetylneuraminyl]-galactosylglucosylceramide). These gangliosides also increased the intensity of the tryptophanyl fluorescence of the isolated A protomer (lambda max = 328 nm). GM1 but not GM2, GM3, and GD1a caused a "blue shift" in the fluorescence spectrum of the B protomer. These results are consistent with other evidence that the specificity of GM1 as the choleragen receptor resides in its carbohydrate moiety. The NADase activity of choleragen was similar to that of diphtheria toxin previously described [J. Kandel, R. J. Collier & D. W. Chung (1974) J. Biol. Chem. 249, 2088-2097]. As with diphtheria toxin, analogues of NAD were inhibitory, adenine being the most effective. Significant inhibition was also noted with adenosine, AMP, ADP-ribose, nicotinamide, nicotinamide mononucleotide, and NADP. NADP was hydrolyzed only slowly by choleragen. In the NADase reaction catalyzed by diphtheria toxin, water serves as an acceptor for the ADP-ribose moiety of NAD in lieu of the natural acceptor molecule, which is elongation factor II (Kandel et al., 1974). It seems probable that the natural protein acceptor for ADP-ribose in the reaction catalyzed by choleragen is adenylate cyclase or a protein component of a cyclase complex that regulates enzymatic activity.
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PMID:Effect of gangliosides and substrate analogues on the hydrolysis of nicotinamide adenine dinucleotide by choleragen. 1 71

Choleragen catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide; nicotinamide production was dramatically increased by L-arginine methyl ester and to a lesser extent by D- or L-arginine, but not by other basic amino acids. Guanidine was also effective. Nicotinamide formation in the presence of L-arginine methyl ester was greatest under conditions previously shown to accelerate the hydrolysis of NAD by choleragen (Moss, J., Manganiello, V. C., and Vaughan, M. (1976) Proc. Natl. Acad. Sci. U.S.A. 73, 4424-4427). After incubation of [adenine-U14C]NAD and L[3H]arginine with coleragen, a product was isolated by thin layer chromatography that contained adenine and arginine in a 1:1 ratio and has been tentatively identified as ADP-ribose-L-arginine. Parallel experiments with [carbonyl-14C]NAD have demonstrated that formation of the ADP-ribosyl-L-arginine derivative was associated with the production of [carbonyl-14C]nicotinamide. As guanidine itself was active and D- and L-arginine was equally effective in promoting nicotinamide production, whereas citrulline, which possesses a ureido rather than a guanidino function, was inactive, it seems probable that the guanidino group rather than the alpha-amino moiety participated in the linkage to ADP-ribose. Based on the assumption that the ADP-ribosylation of L-arginine by choleragen is a model for the NAD-dependent activation of adenylate cyclase by choleragen, it is proposed that the active A protomer of choleragen catalyzes the ADP-ribosylation of an arginine, or related amino acid residue in a protein, which is the cyclase itself or is critical to its activation by choleragen.
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PMID:Mechanism of action of choleragen. Evidence for ADP-ribosyltransferase activity with arginine as an acceptor. 13 9

The effect of cholera toxin on adenylate cyclase from rat liver has been studied in a broken cell preparation. The activation of the enzyme in this in vitro preparation requires the addition of nicotinamide adenine dinucleotide (NAD) to the incubation medium and the presence of cell components other than the membrane-bound adenylate cyclase. Once the activation of the cyclase is produced, the effect persists despite repeated washing or solubilization of the enzyme. The effect can be obtained with concentrations of cholera toxin as low as 0.4 nM after 15 min of incubation at 22 degrees C, and stimulation can be detected after only 5 min of incubation at 37 degrees C. The activation of the enzyme is still apparent after at least 2 h at 0 degrees C. Preincubation with choleragenoid in vitro does not interfere with this effect of the toxin. Animals pretreated by an intravenous injection of cholera toxin do not respond to the in vitro addition of cholera toxin and NAD to the same extent as untreated animals; i.e., the effects overlap to suggest that the in vitro effect is the same as that in vivo. Responses to isoproterenol, glucagon, and NaF were also similar in the in vitro broken cell-activated system, as previously reported for the enzyme activated in vivo.
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PMID:Activation of adenylate cyclase by cholera toxin in rat liver homogenates. 17 81

Heat-labile enterotoxic material released from Escherichia coli by polymyxin B activates the adenylate cyclase of pigeon erythrocyte ghosts in a time- and concentration-dependent manner. The activation requires nicotinamide adenine dinucleotide, adenosine triphosphate, and another component of the erythrocyte supernatant. The active species has a molecular weight of about 23,000-24,000 daltons, is inhibited by antibodies to the toxin of Vibrio cholerae, and is not irreversibly denatured by sodium dodecyl sulfate. Thus in many respects the active species from E. coli behaves the same as peptide A1 of cholera toxin.
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PMID:Mechanism of activation adenylate cyclase in vitro by polymyxin-released, heat-labile enterotoxin of Escherichia coli. 17 79

Peptide A1 of Vibrio cholerae toxin, nicotinamide adenine dinucleotide, adenosine triphosphate, and a soluble protein present in erythrocyte supernatant are required for the activation of pigeon erythrocyte ghost adenylate cyclase but are not required to maintain the activated state. The compounds are all required simultaneously, and when all are added to ghosts, adenylate cyclase activity increases at a linear rate without delay. Under optimal conditions significant activation of cyclase is given by less than one molecule of toxin per ghost. Intact cholera toxin may be inactive in vitro. There is a delay of about 1 min between the addition of intact toxin and the attainment of the final rate of increase of adenylate cyclase activity. During this period, glutathione reduces the disulfide bond between peptides A1 and A2. The delay is eliminated if the toxin is reduced before addition. More A1 is liberated if the toxin is also denatured with sodium dodecyl sulfate.
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PMID:Multiple roles of erythrocyte supernatant in the activation of adenylate cyclase by Vibrio cholerae toxin in vitro. 17 81

Three discrete phases are discernible in the activation, by Vibrio cholerae toxin, of adenylate cyclase in fragments of sarcoma 180 cell membranes. In the first, or preparatory, phase the toxin must be exposed to dithiothreitol or nicotinamide adenine dinucleotide (NAD) in the absence of the membranes. In the second phase, the prepared toxin is dissociated to yield a macromolecular cyclase-activating factor (MCAF) in the presence of the membranes. In the third phase, membrane basal adenylate cyclase is activated by MCAF in the presence of NAD. The integrity of the catecholamine or beta-receptor associated with sarcoma adenylate cyclase is irrelevant in the activation of cyclase by MCAF. This activation proceeds undiminished even if the beta-receptor is desensitized or blocked by propranolol.
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PMID:Interaction of Vibrio cholerae toxin with sarcoma 180 cell membranes. 17 83

The application of cholera toxin to intact cells causes a stimulation of adenylate cyclase activity. The effect is characterized by a lag period followed by a progressive rise in enzyme activity over several hours. Only a few minutes' exposure to the toxin is required to produce effects lasting over several days. Stimulation of adenylate cyclase by cholera toxin in broken cell preparations requires the presence of nicotinamide-adenine dinucleotide (NAD) and an unidentified component of the cytosol. Guanyl nucleotides and certain non-hydrolysable analogues of guanosine triphosphate also stimulate adenylate cyclase. Stimulation by the analogues results in a highly activated enzyme which has characterisitcs similar to those of adenylate cyclase after stimulation by cholera toxin. Thus the stimulation is irreversible, the enzyme may be "solubilized" by non-ionic detergents in the activated state, and responses to certain hormones are enhanced. Therefore the possibility exists that cholera toxin acts on the guanyl nucleotide regulatory protein of the adenylate cyclase complex. In exploring this possibility it was found pretreatment with cholera toxin not only blocked the stimulatory effect of subsequently added guanylylimidodi-phosphate (GppNHp) but that the latter reduced the stimulation by toxin. Similarly, pretreatment with GppNHp blocked the effect of cholera toxin. The similarities in the effects of cholera toxin and GppNHp, together with the mutual interference of their activities, suggests that cholera toxin acts at the same regulatory site at which guanyl nucleotides exert their effects on adenylate cyclase.
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PMID:The activation of adenylate cyclase by cholera toxin: possible interaction with the nucleotide regulatory site. 18 40

Choleragen and the isolated A protomer catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide. The protein with NADase activity (NAD nucleosidase; NAD glycohydrolase, EC 3-2-2-5) migrated on polyacrylamide gels with choleragen, and chromatographed on Bio-Gel P-60 columns with the A protomer. The NADase activity of choleragen and of the A protomer was increased markedly in acetate and phosphate buffers, and enhanced over 10-fold by dithiothreitol in high concentration. NAD hydrolysis was proportional to choleragen concentration; the Michaelis constant for NAD was about 4 mM with both choleragen and the A protomer. The demonstration that the A protomer of choleragen catalyzes an enzymatic reaction involving activation of the ribosyl-nicotinamide bond of NAD, a reaction analogols to those catalyzed by diphtheria toxin, supports the hypothesis that activation of adenylate cyclase by choleragen involves the ADP-ribosylation of an appropriate acceptor protein.
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PMID:Hydrolysis of nicotinamide adenine dinucleotide by choleragen and its A protomer: possible role in the activation of adenylate cyclase. 18 38

The effects of glucose, a series of glucose metabolites, nicotinamide nucleotides, Ca2+ and p-chloromercuribenzenesulphonate on adenylate cyclase activity in homogenates of mouse pancreatic islets were studied. The basal activity of the adenylate cyclase was approx. 6 pmol of cyclic AMP formed/30 min per microng of DNA at 30 degrees C. The enzyme activity was stimulated by some 150% by fluoride. Starvation of the animals for 48h had no effect on either the basal or the fluoride-stimulated activity. The adenylate cyclase activity was increased by 40-50% when 17 mM-glucose, 10 micronM-phosphoenolpyruvate or 10 micronM-pyruvate was added to the assay medium. The effect of glucose was unchanged in the presence of 17 mM-mannoheptulose, and mannoheptulose alone had no effect. The other glycolytic intermediates, and the coenzymes NAD+, NADH and NADPH, at concentrations up to 1 mM were without any detectable effect on the rate of formation of cyclic AMP. The insulin secretagogue p-chloromercuribenzenesulphonate inhibited the adenylate cyclase markedly even at a concentration of 10 micronM. Calculated concentrations of free Ca2+ of 10 micronM and 0.1 mM inhibited adenylate cyclase by 29 and 71% respectively. It is concluded that both glucose itself and phosphoenolpyruvate and/or pyruvate are true activating ligands for islet and adenylate cyclase and that inhibition of the cyclase by Ca2+ may be of physiological significance.
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PMID:Effects of glucose, glucose metabolites and calcium ions on adenylate cyclase activity in homogenates of mouse pancreatic islets. 19 80

Treatment of pigeon erythrocyte membranes with cholera toxin and NAD(+) enhanced the GTP stimulation and suppressed the F(-) activation of the adenylate cylase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1]. In the presence of NAD(+) labeled with (32)P in the AMP moiety the toxin catalyzed the covalent incorporation of radioactivity into membrane proteins with molecular weights (M(r)s) of 200,000, 86,000, and 42,000. Extraction of toxin-treated membranes with Lubrol PX followed by affinity chromatography on a GTP-Sepharose column resulted in a 200-fold purification of the 42,000-M(r) labeled protein and in its complete separation from the other labeled proteins. The fraction containing the purified GTP-binding component from toxin-treated membranes conferred an enhanced GTP-stimulated activity on adenylate cyclase solubilized from nontreated membranes. Likewise, the addition of GTP-binding fraction from nontreated membranes to an enzyme solubilized from toxin-treated membranes restored F(-) stimulation of the adenylate cyclase. The toxin-induced modification of adenylate cyclase and the incorporation of radioactivity into the 42,000-M(r) protein were partially reversed upon incubation with toxin and nicotinamide at pH 6.1. The results indicate that cholera toxin affects the adenylate cyclase system by catalyzing an ADP-ribosylation of the 42,000-M(r) component bearing the guanyl nucleotide regulatory site.
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PMID:Mechanism of cholera toxin action: covalent modification of the guanyl nucleotide-binding protein of the adenylate cyclase system. 20 69


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