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)

Adrenergic mechanism for phosphorylase activation was gradually converted from an alpha 1- to a beta 2-type during primary culture of rat hepatocytes. beta 2-Receptor-mediated cAMP generation was also much greater in 8-h cultured cells than in fresh cells. Incubation of hepatocyte membranes with [alpha-32P]NAD and the preactivated A-protomer (an active component) of islet-activating protein (IAP), pertussis toxin, resulted in the ADP-ribosylation of a specific IAP substrate protein (Mr = 41,000). This ADP-ribosylation diminished progressively when the membrane-donor hepatocytes had been cultured. The early diminution was interfered with by the addition of nicotinamide or isonicotinamide, a potent inhibitor of ADP-ribosyltransferase, to the culture medium. The decrease of the IAP substrate was well correlated with the potentiation of beta-adrenergic functions under various conditions of culture. beta-Receptor-mediated activation of GTP-dependent membrane adenylate cyclase was, but glucagon-induced activation was not enhanced by either prior culture of hepatocytes or prior exposure of membranes to the A-protomer of IAP. There was no further enhancement, however, when membranes from cultured cells were exposed to the active toxin. Thus, the IAP-susceptible inhibitory guanine nucleotide-regulatory protein is coupled to beta-adrenergic receptors in such a manner as to reduce the degree of activation of cyclase, and the decrease in this IAP substrate may be responsible, at least partly, for development of beta-receptor functions during culture of hepatocytes. Its possible relation to accompanying inhibition of alpha 1-receptor functions is discussed.
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PMID:Conversion of adrenergic mechanism from an alpha- to a beta-type during primary culture of rat hepatocytes. Accompanying decreases in the function of the inhibitory guanine nucleotide regulatory component of adenylate cyclase identified as the substrate of islet-activating protein. 609 73

The light chain of type C2 toxin produced by Clostridium botulinum was isolated by high-performance liquid chromatography. The protein eluted as a single peak; as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, it had an apparent molecular weight of 51,000 daltons. The light chain was an enzyme that possessed ADP-ribosylating activity. In experiments with synthetic substrates (homo-poly-L-amino acids; alanine, arginine, asparagine, aspartic acid, histidine, leucine, lysine, methionine, phenylalanine, proline, serine and tryptophan), only poly-L-arginine was ADP-ribosylated by the enzyme. In experiments with endogenous substrates (50,000 X g pellet and 50,000 X g supernatant from homogenates of mouse brain, liver and lung), the enzyme ADP-ribosylated proteins or polypeptides in both the particulate and soluble fractions. ADP-ribosylation of the soluble substrate was antagonized by adenine (K1 approximately 2.1 X 10(-5) M) and by adenosine (K1 approximately 2.7 X 10(-4) M); the reaction was reversed by a large molar excess of nicotinamide (0.1 M). ADP-ribosylation of soluble substrate was diminished when the substrate had been pretreated with 1,2-cyclohexane-dione (0.1 M), a site reactive reagent that modified selectively arginine residues. Neither the light chain nor the heavy chain of the binary toxin possessed adenylate cyclase activity. Tissue fractions did possess endogenous adenylate cyclase activity, but the toxin did not stimulate this activity. The data indicate that the binary toxin produced by Clostridium botulinum resembles other protein toxins.
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PMID:Molecular basis for the pharmacological actions of Clostridium botulinum type C2 toxin. 623 95

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

Growth of Bordetella pertussis in a high concentration of nicotinic acid (NA) had a modulating effect on several properties and activities of the bacteria. Compared with normally grown cells, those grown in a high concentration of NA had reduced capacity for taking up both NA and nicotinamide (ND); they had reduced adenylate cyclase activity and showed loss of agglutinogen factors 2 and 3, but an increase in factor 1. By contrast, cells grown in a high concentration of ND showed only a slightly decreased capacity for uptake of ND and none of the other changes. Modulation of B. pertussis by NA varied with the strain and culture conditions and appeared to be distinct from the antigenic modulation induced by high Mg2+ in the culture medium. Evidence is presented for the association of a small proportion of the extracytoplasmic adenylate cyclase with the outer membrane of B. pertussis.
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PMID:Modulation of Bordetella pertussis by nicotinic acid. 630 72

Pertussis toxin (islet-activating protein) activates adenylate cyclase in susceptible cells by ADP-ribosylating an inhibitory component of the cyclase system. This toxin, assayed in a cell-free system in the presence of high concentrations of thiol, catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide. This NAD glycohydrolase activity co-chromatographed on Sephacryl G-200 in 6.5 M urea, pH 3.2, 0.1 M glycine with the ADP-ribosyltransferase activity of the toxin, as monitored by the transfer of [32P]ADP-ribose from [32P]NAD to a 41,000-Da protein in NG108-15 neuroblastoma X glioma hybrid cells. In the absence of thiol, the native holotoxin was enzymatically inactive. Following addition of 250 mM dithiothreitol to the assay, maximal enzymatic activity was evident after a delay of approximately 1 h; with 20 mM thiol, the delay was longer. The Km for NAD with the fully activated enzyme was 25 microM; the Km did not appear to vary with the extent of activation. Thiol was necessary in a cell-free system to demonstrate NAD glycohydrolase activity. When extensively washed membranes were used as a source of 41,000-Da substrate, thiol was necessary to observe ADP-ribosylation in some cases (human erythrocytes) and significantly stimulated activity in others (NG108-15 cells). In contrast to the bacterial toxins choleragen and Escherichia coli heat-labile enterotoxin that ADP-ribosylate stimulatory components of the cyclase system, pertussis toxin did not transfer ADP-ribose to low molecular weight guanidino compounds, such as arginine or agmatine.
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PMID:Activation by thiol of the latent NAD glycohydrolase and ADP-ribosyltransferase activities of Bordetella pertussis toxin (islet-activating protein). 631 27

Nicotinamide injected in a high dose (100 mg/100 g body weight) into rats induces several variations both of enzymatic activities and of metabolites levels. We have tested the effect of NAm on liver cAMP content; it increases reaching a peak at the second hour after treatment. Liver adenylate cyclase and 3',5'-cyclic AMP phosphodiesterase activities have been tested; the former increases reaching a peak after 1 hour, while the latter decreases consistently one hour after treatment. This variation of cAMP phosphodiesterase activity could be related to the change of the pyridine coenzymes redox state observed after NAm injection. The increase of the liver cAMP concentration could explain the mobilization of glucose after treatment with NAm, and the alteration of several enzymatic activities, as serine dehydratase, observed after treatment.
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PMID:Metabolism of adenosine-3', 5'-cyclic monophosphate in the liver of rats treated with nicotinamide. 631 8

1. Cholera toxin was shown to require the presence of GTP to activate rat liver plasma-membrane adenylate cyclase. ATP did not affect the activation process. 2. Cholera toxin catalysed the incorporation of 32P from NAD labelled in the alpha-phosphate group of the ADP moiety into a rat liver plasma-membrane protein with a subunit mol.wt. of 42 500. This is taken to demonstrate ADP-ribosylation. The ADP-ribosylation of this protein also required GTP and was unaffected by ATP. 3. Nicotinamide inhibited both the activation of adenylate cyclase by cholera toxin and the ADP-ribosylation of the protein of 42 500 subunit mol wt. Neither the activation nor the ADP-ribosylation could be reversed by treatment with nicotinamide in the presence of cholera toxin.
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PMID:Requirement for guanosine triphosphate for cholera-toxin-catalysed incorporation of adenosine diphosphate ribose into rat liver plasma membranes and for activation of adenylate cyclase. 644 2

A model system, measuring the rate of cholera-toxin-catalysed release of nicotinamide from NAD+, has been used to identify novel compounds which may serve as substrates for toxin-directed ADP-ribosylation. In a series of guanidine-containing compounds, those in which the guanidine group was connected to a large hydrophobic domain greatly stimulated the rate of toxin-catalysed nicotinamide release. The introduction of a charge centre near the guanidine group destroyed all activity. The compounds thus identified were found to inhibit the action of cholera toxin on rat liver adenylate cyclase, and this was associated with a reduction in the amount of [32P]ADP-ribosylation of a 42-kDa protein in the membranes. Guanidine-containing compounds which did not enhance toxin-catalysed release of nicotinamide from NAD+ had no effect on toxin action on adenylate cyclase, and there was a good correlation between the two activities. The results are discussed in relation to the known properties of the guanine nucleotide regulatory protein associated with adenylate cyclase systems, which is the toxin's natural substrate.
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PMID:Artificial low-molecular-mass substrates of cholera toxin. 646 87

The heat-labile enterotoxin of Escherichia coli, like cholera toxin, activates adenylate cyclase by catalyzing the transfer of adenosine diphosphate-ribose from HAD+ (oxidized nicotinamide adenine dinucleotide) to the guanyl nucleotide-dependent regulatory component of the cyclase. A preparation of enterotoxin that had been released from E. coli following exposure to polymyxin B and then partially purified was found to contain two enzymatically active peptides, one of about 29,000 and the other of about 24,000 daltons, which correspond in molecular size to the enzymatically active subunit A and fragment A1 of cholera toxin, respectively. As with cholera toxin, the enzymatic activity of E. coli enterotoxin was elevated by incubation with sodium dodecyl sulfate to release active peptides. Treatment with dithiothreitol, however, had no effect. Dithiothreitol activates subunit A of cholera toxin by reducing an internal disulfide bond, but no corresponding bond appears to be present in the partially purified E. coli enterotoxin.
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PMID:Adenosine diphosphate-ribosylation of adenylate cyclase catalyzed by heat-labile enterotoxin of Escherichia coli: comparison with cholera toxin. 698 18

Islet-activating protein (IAP), one of the pertussis toxins, exerted dual actions on crude membrane preparations from rat C6 glioma cells; an Mr = 41,000 membrane protein was ADP-ribosylated while GTP (and GTP-dependent isoproterenol) activation of membrane adenylate cyclase was enhanced when membranes were incubated with IaP. Both actions of IaP were dependent on the incubation time and the concentrations of NAD and IAP, and were inhibited by nicotinamide; the one action was strictly paralleled by the other in magnitude. Tryptic digestion of the Mr = 41,000 protein was markedly influenced by the presence of guanyl-5'-yl beta-gamma-imidodiphosphate or NaF, the specific ligands of the regulatory component of the adenylate cyclase system. No ADP ribosylation occurred in the membranes prepared from intact C6 cells that had been incubated with IAP, suggesting that the IAP substrate had already been ADP-ribosylated by the intracellular NAD during incubation of the intact cells. Cholera toxin catalyzed ADP ribosylation of other proteins with Mr = 45,000 and 48,000/49,000 (doublet). It is concluded that IAP, added to intact cells or isolated membranes, causes unique modification of the receptor-adenylate cyclase coupling mechanism as a result of ADP ribosylation of the Mr = 41,000 protein which is presumably one of the subunits, other than the cholera toxin substrates, of the guanine nucleotide regulatory component of the cyclase system.
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PMID:ADP ribosylation of the specific membrane protein of C6 cells by islet-activating protein associated with modification of adenylate cyclase activity. 720 Sep 79


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