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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↗
PubMed1980

Streptococcal extracellular NAD+ nucleosidase. Characterization of changes occurring during purification.

Purification of streptococcal extracellular NAD+ nucleosidase is associated with changes of kinetic properties. A high-molecular weight component is required for a full activity of the enzyme. The component is not produced by bacteria and is present in the Todd-Hewitt cultivation medium, the beef-heart extract serving primarily as its source. In its effect on the enzyme this component can be replaced with bovine albumin. It follows from the time relationship of the NAD decomposition that the mechanism of the studied enzymic reaction is not hydrolytic. In addition to nicotinamide, a product of polymeric character is formed.

Animals↗
PubMed2001

Kinetic properties of fractions of extracellular NAD+ nucleosidase from Streptococcus pyogenes as an example of host selection by a pathogen: possible role of serum albumin in the organism.

Preparative isoelectric focusing was used to separate free bacterial NAD+ nucleosidase from its complex with a bound host component. Both fractions were characterized by optimum temperature and activation energy of denaturation. The bacterial product is enzymically inactive. The enzymically active structure is formed upon binding to the host component. Only the host organism can provide the suitable, activating structure. The host component in the present system is added to the cultivation medium with a beef heart extract but it can be replaced by serum albumin. The possible role of albumin as a carrier structure for flexible and enzymically inactive peptides is discussed. Different peptides bound to albumin can provide different enzyme activities. The term binary enzyme is coined, referring to a situation where the two enzyme components are coded at genetically distant loci. The pathogen makes use of the carrier structure of albumin type and produces another polypeptide invested with an enzyme activity convenient for the pathogen.

Culture Media↗
PubMed1983

A quantitative assay for the cytoplasmic androgen receptor using [3H]dihydrotestosterone in the presence of NAD+-nucleosidase.

In prostatic cytosol DHT1 is metabolized to 5 alpha-androstane-3 alpha (or beta), 17 alpha-diols with a half life of 2 h even at 4 degrees C. Thus, [3H]DHT appears to be a poor marker for a quantitative assessment of androgen receptors (AR). Methyltrienolone (R1881) seems to be advantageous as it is not metabolized. However, because of considerable binding to progestin receptors, assays using [3H]R1881 are not specific for AR in tissues containing progestin receptors. We, therefore, developed a specific assay for AR using [3H]DHT (14 nM) as marker, where metabolism of DHT is prevented by pre-incubation with NAD+-nucleosidase. The [3H]DHT-receptor complex is separated from free, SHBG-bound and unspecifically bound [3H]DHT by agar gel electrophoresis. The binding sites of high affinity and low capacity are characterized by suppression with unlabelled R1881 (2 microM) in a parallel assay. Under these conditions DHT and R1881 appear to have the same kinetics of association and dissociation. Weighted non-linear regression analysis of specific binding capacity at various ligand concentrations reveals that in rat prostatic cytosol the affinity of DHT (Kd = 0.405 +/- 0.0839 nM) is significantly higher (P less than 0.01) than that of R1881 (Kd = 1.25 +/- 0.271 nM).

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↗
PubMed1987

Asymmetric reassociation of calf spleen NAD+ glycohydrolase into liposomes.

NAD+ glycohydrolase (NAD+ nucleosidase, EC 3.2.2.6) can be solubilized from calf spleen microsomes (microsomal fractions) by steapsin or by detergents to yield respectively a hydrophilic (i.e. water-soluble) and a hydrophobic form of the enzyme. The detergent-solubilized enzyme was successfully reassociated into phosphatidylcholine liposomes either by a cholate-dialysis or by a gel-filtration procedure. In both cases the incorporation of NAD+ glycohydrolase was found to be completely asymmetric, i.e. the active site of the enzyme was exposed only at the outer surface of the vesicles. By contrast, as judged by flotation experiments, the hydrophilic form of NAD+ glycohydrolase could not be reassociated into liposomes. These results are in agreement with the hypothesis that calf spleen NAD+ glycohydrolase is an amphipathic protein. When incorporated into large unilamellar vesicles composed of phosphatidylcholine, NAD+ glycohydrolase was not found to catalyse vectorial transfer of NAD+ by transglycosidation with nicotinamide as acceptor.

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↗