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Results for “NAD+ Nucleosidase”

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At least 19 recordsLinked to original sources
PubMed1978

NAD nucleosidase of Agkistrodon bilineatus venom.

NAD nucleosidase (NAD glycohydrolase, EC 3.2.2.5) activity in Agkistrodon bilineatus venom was observed. Using the cyanide assay method at pH 7.9, lyophilized crude venom had an activity of 0.19 units/mg. Chromatography of the crude venom on DEAE Sephadex A-50 with ammonium acetate buffer by two stage elution yielded 13 fractions. Peak NAD nucleosidase activity occurred at Fraction X. Crude venom and Fraction X NAD nucleosidase activities were thermolabile.

Animals↗
PubMed1975

Evidence for NAD nucleosidase in rabbit-liver lysosomes.

A method is described for the isolation of secondary lysosomes from homogenates of rabbit liver; The uptake of Triton WR-1339 by rabbit-liver lysosomes when administered by intraperitoneal injection was used to decrease the density of secondary lysosomes. Lysosomal fractions prepared by this method contain an NAD nucleosidase (NAD glycohydrolase, EC 3;2.25), an enzyme which has previously been considered to be associated with other subcellular fractions. The enzyme has maximum activity at pH 6 and cleaves both NAD and NADP. It is inhibited by nicotinamide (Ki equals 4.5 mM) and by HgCl2. Both nucleosidase and 2'-nucleotidase show in-vitro latency typical of lysosomal acid hydrolases. Rabbit-liver plasma-membrane fractions were isolated which contained most 5'-nucleotidase but relatively little nucleosidase, whereas rabbit liver lysosomes contain both 5'-nucleotidase and nucleosidase enzymes but little adenyl cyclase.

Animals↗
PubMed1976

Hydrolysis of nicotinamide adenine dinucleotide by choleragen and its A protomer: possible role in the activation of adenylate cyclase.

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.

Adenylyl Cyclases↗
PubMed1976

The effect of egg phospholipid administration upon liver enzymic activities during ethionine treatment.

Female rats were injected subcutaneously with ethionine, and enzymic activities of liver membranes (Na+-k+-stimulated ATPase, Mg2+-stimulated ATPase, glucose-6-phosphatase, NADPH: cytochrome c oxido-reductase and NAD-nucleosidase) examined at proper intervals, during the intraperitoneal treatment of an egg phospholipid preparation (EPL). It is shown that EPL is unable to overcome the enzymic changes due to severe ethionine treatment, but is able to facilitate the recovery times after drug withdrawal for all the enzymic activities, except for NAD-nucleosidase. At lower dosage of the drug, the ethionine treatment is able to prevent the observed change of the glucose-6-phosphatase activity but not that of the Mg2+-ATPase. It is suggested that the EPL treatment may modify the chemical composition ahd/or architecture of liver membranes, altered by the ethionine injection, thus acting, at least partially, on the enzymic changes.

Adenosine Triphosphatases↗
PubMed1975

Pyridine nucleosidase in bull semen. II. Biochemical properties.

It is most likely a single enzyme (NAD+ nucleosidase) present in semen from most bulls which hydrolyses the ribosyl pyridinium bond in both NAD and NADP. This conclusion is based on the following results: (i) each of 12 semen samples containing nucleosidase activity hydrolysed NAD at the same rate as NADP (r = 0.99); (ii) other untreated semen samples from different bulls which did not hydrolyse NAD were also inactive against NADP; (iii) enzyme denaturation produced by preliminary heating of semen filtrates for 15 min at varied temperatures or by heating at 55 degrees C for varied time intervals caused similar reductions in the rates of NAD and NADP hydrolysis; and (iv) nicotinamide inhibited enzyme activity to the same degree using either NAD or NADP as the substrate.

Animals↗
PubMed1978

Purification and some properties of NAD-degrading purine nucleosidase from Aspergillus niger.

An enzyme which degrades NAD at the adenine-ribose linkage has been purified from the mycelial extract of Aspergillus niger. NADP, deamido-NAD, and purine nucleosides and nucleotides were also susceptible to the hydrolytic cleavage. Pyrimidine- and nicotinamide-ribose linkages were not attacked. The substrate specificity showed that the enzyme may be classified as a N-ribosyl-purine ribohydrolase (EC 3.2.2.1). The enzyme had a maximum activity in the pH range of 4.0-4.5 toward NAD. The Km values for NAD, 5'-AMP, and inosine were 3.0, 2.9 and 1.6mM respectively.

Aspergillus niger↗
PubMed1977

The influence of adrenalectomy on monoamine oxidase and NADH cytochrome c reductase in the rat heart.

The effect of adrenalectomy on the activities of monoamine oxidase (MAO), NADH cytochrome c reductase (NCR), succinate dehydrogenase, malate dehydrogenase, fumarase, NAD+ nucleosidase and acid phosphatase in homogenates of rat hearts was examined. Besides MAO only the NCR activity increased. However, both the total and the rotenone-insensitive NCR activities increased, with that of the rotenone-insensitive being about half of the total, which indicated that the effect of adrenalectomy was exerted on components of this enzyme localized on both the inner and outer membranes of the mitochondrion. The lack of effect on the other enzymes suggests that adrenalectomy has a relatively selective action on MAO and NCR, and does not work by a generalized increase in protein synthesis or by an effect on the FAD cofactor. The MAO increase was seen with a variety of substrates, and was due to a rise in Vmax without change in Km. The response to adrenalectomy in the summer differed from that seen in the winter. The possible reasons for these effects of adrenalectomy are discussed.

Adrenalectomy↗
PubMed1978

Respiration and oxidative phosphorylation in Treponema pallidum.

Exogenous and endogenously generated reduced pyridine nucleotides caused marked stimulation of O(2) uptake when added to treponemal cell-free extracts, which indicated that terminal electron transport was coupled to the consumption of O(2). Oxidation of reduced nicotinamide adenine dinucleotide (NADH) was shown to correlate stoichiometrically with O(2) reduction, suggesting that NADH was being oxidized through a mainstream respiratory chain dehydrogenase. Oxygen evolution in treponemal extracts was observed after the completion of O(2) uptake which was stimulated by exogenous NADH and endogenously generated reduced NAD phosphate. Oxygen evolution was inhibited by both cyanide and pyruvate, which was consistent with O(2) release from H(2)O(2) by catalase. The addition of exogenous H(2)O(2) to treponemal extracts caused rapid O(2) evolution characteristic of a catalase reaction. A spectrophotometric assay was used to measure ATP formation in T. pallidum cell-free extracts that were stimulated with NADH. P/O ratios from 0.5 to 1.1 were calculated from the amounts of ATP formed versus NADH oxidized. Phosphorylating activity was dependent on P(i) concentration and was sensitive to cyanide, N, N'-dicyclohexylcarbodiimide, and carbonyl cyanide m-chlorophenyl hydrazone. Adenine nucleotide pools of T. pallidum were measured by the firefly luciferin-luciferase assay. Shifts in adenine nucleotide levels upon the addition of NADH to cell-free extracts were impossible to evaluate due to the presence of NAD(+) nucleosidase. However, when whole cells, previously incubated under an atmosphere of 95% N(2)-5% CO(2), were sparged with air, ATP and ADP levels increased, while AMP levels decreased. The shift was attributed to both oxidative phosphorylation and to the presence of an adenylate kinase activity. T. pallidum was also found to possess an Mg(2+) - and Ca(2+) -stimulated ATPase activity which was sensitive to N, N' -dicyclohexylcarbodiimide. These data indicated a capability for oxidative phosphorylation by T. pallidum.

Adenine Nucleotides↗
PubMed1978

Mechanism of action of choleragen.

Choleragen exerts its effect on cells through activation of adenylate cyclase. Choleragen initially interacts with cells through binding of the B subunit of the toxin to the ganglioside GM1 on the cell surface. Subsequent events are less clear. Patching or capping of toxin on the cell surface may be an obligatory step in choleragen action. Studies in cell-free systems have demonstrated that activation of adenylate cyclase by choleragen requires NAD. In addition to NAD, requirements have been observed for ATP, GTP, and calcium-dependent regulatory protein. GTP also is required for the expression of choleragen-activated adenylate cyclase. In preparations from turkey erythrocytes, choleragen appears to inhibit an isoproterenol-stimulated GTPase. It has been postulated that by decreasing the activity of a specific GTPase, choleragen would stabilize a GTP-adenylate cyclase complex and maintain the cyclase in an activated state. Although the holotoxin is most effective in intact cells, with the A subunit having 1/20th of its activity and the B subunit (choleragenoid) being inactive, in cell-free systems the A subunit, specifically the A1 fragment, is required for adenylate cyclase activation. The B protomer is inactive. Choleragen, the A subunit, or A1 fragment under suitable conditions hydrolyzes NAD to ADP-ribose and nicotinamide (NAD glycohydrolase activity) and catalyzes the transfer of the ADP-ribose moiety of NAD to the guandino group of arginine (ADP-ribosyltransferase activity). The NAD glycohydrolase activity is similar to that exhibited by other NAD-dependent bacterial toxins (diphtheria toxin, Pseudomonas exotoxin A), which act by catalyzing the ADP-ribosylation of a specific acceptor protein. If the ADP-ribosylation of arginine is a model for the reaction catalyzed by choleragen in vivo, then arginine is presumably an analog of the amino acid which is ADP-ribosylated in the acceptor protein. It is postulated that choleragen exerts its effects on cells through the NAD-dependent ADP-ribosylation of an arginine or similar amino acid in either the cyclase itself or a regulatory protein of the cyclase system.

Adenylyl Cyclases↗
PubMed1976

Poly ADP-ribosylation of DNA-dependent RNA polymerase I from quail oviduct. Dependence on progesterone stimulation.

Progesterone causes in goblet cells of oviducts of estrogen hormone-stimulated immature quails selectively gene activation without affecting DNA synthesis. This biological model has been used to study the influence of poly ADP-ribosylation during the processes of DNA transcription. Administration of progesterone in vivo causes an increase of the activity of RNA polymerase I and II in isolated nuclei. This increase is accompanied by a marked decrease of the specific activity of poly (ADP-Rib) polymerase. After in vitro ADP-ribosylation of nuclear proteins the template capacity of chromatin for ""exogenous'' RNA synthesis (with E. coli DNA-dependent RNA polymerases) as well as for ""endogenous'' RNA synthesis with DNA dependent RNA polymerases II is not affected, whereas the data presented seem to indicate that the capacity for RNA synthesis mediated by ""endogenous'' DNA-dependent RNA polymerase I might be inhibited after ADP-ribosylation. Evidence is presented to show that a considerable amount of poly (ADP-Rib), synthesized by poly (ADP-Rib) polymerase in isolated nuclei, is linked with RNA polymerase I. The rate of synthesis of poly (ADP-Rib) is dependent on the incubation temperature (optimum at 25 degrees C) and it can be inhibited by the specific inhibitors of poly (ADP-Rib) polymerase nicotineamide, thymidine and formycin B. Poly (ADP-Rib) is probably associated with RNA polymerase I through a covalent linkage. ADP-ribosylated RNA polymerase I has been purified 550 fold with respect to the nuclear extract corresponding to a 4,000 fold purification from the whole cell homogenate. The ratio between poly (ADP-Rib), formed during preincubation of nuclei with NAD, and RNA polymerase I remains almost constant during the purification procedures. The extent of ADP-ribosylation of RNA polymerase I decreases during gene expression. Thus we conclude that poly ADP-ribosylation of this enzyme is one of the regulatory mechanisms by which specificity of DNA transcription is achieved.

Animals↗
PubMed1977

Streptococcal extracellular NAD-glycohydrolase. Optimal temperature and activation by cysteine.

Streptococcal extracellular NAD-glycohydrolase (EC 3.2.2.5) exists in two distinct states with respect to the optimal reaction temperature. Bacteria produce the enzyme form with optimum activity at about 40 degress C. Probably due to oxygen action, the enzyme is converted to a form with optimum activity at 30 degrees C. Compounds of the type of cysteine restore the initial state. The conversions are accompanied by enzyme activity fluctuations.

Cysteine↗