NAD Metabolism Research Articles

Influence of d-galactosamine upon the nad-metabolism in rat liver

1. After application of d-galactosamine a hepatitis develops in the rat liver. This can be prevented by different agents, including tryptophan. Yet it has not been possible to give definitive conclusions about the mechanism of galactosamine hepatitis. In this paper we report about the influence of galactosamine on the NAD metabolism. 2. 1. d-galactosamine inhibits the NAD synthesis initiated by nicotinamide in normal and adrenalectomized animals. 3. 2. The NAD synthesis from tryptophan is prevented in normal animals, in adrenalectomized ones however there is an increase of NAD in the presence of d-galactosamine. 4. 3. d-galactosamine reduces the activity of the ADPR transferase. 5. 4. Inhibitors of the ADPR transferase prevent the galactosamine hepatitis. 6. 5. From the results presented we conclude that the ADPR transferase plays an important role in the development of the galactosamine hepatitis.

Metabolism of NAD by isolated rat renal brush border membranes.

NAD and NADH are metabolized to adenosine, ribosyl nicotinamide and Pi by isolated rat renal brush border membranes (BBM). The similar distribution like the BBM marker enzyme alkaline phosphatase indicates that nucleotide pyrophosphatase and 5-nucleotidase are BBM enzymes.

1-Methylnicotinamide and NAD metabolism in normal and transformed normal rat kidney cells

NAD, 1-methylnicotinamide, S-adenosylmethionine, and S-adenosylhomocysteine levels were analyzed in different clones of untransformed normal rat kidney cells and in cells transformed by different viruses. No consistent changes in the levels of these metabolites were apparent as a result of malignant transformation, and also differences in the levels of metabolites did not correlate with growth rate in the various cell lines. 3-Deazaadenosine prevented synthesis of 1-methylnicotinamide but not of NAD. The S-denosylmethionine/ S-adenosylhomocysteine ratio did not change in serum-starved, growth-arrested cells although 1-methylnicotinamide synthesis increased about twofold. These results were used to consider possible physiological roles for 1-methylnicotinamide. Its intracellular levels did not correlate with growth rate and were not altered by transformation. No evidence was obtained that its synthesis is involved with maintenance of nicotinamide of S-adenosylmethionine levels. Thus the biological function for 1-methylnicotinamide remains a mystery.

Effects of nicotinamide on NAD and poly(ADP-ribose) metabolism in DNA-damaged human lymphocytes.

The effect of nicotinamide on unscheduled DNA synthesis was studied in resting human lymphocytes. In cells treated with UV irradiation or with MNNG, nicotinamide caused a two-fold stimulation of unscheduled DNA synthesis and retarded the rate of NAD+ lowering caused by these treatments. Nicotinamide also reduced the burst of poly(ADP-ribose) synthesis caused by MNNG treatment. Thus under conditions that it enhances unscheduled DNA synthesis, nicotinamide causes marked effects on the metabolism of NAD+ and poly(ADP-ribose). The effect of nicotinamide on unscheduled DNA synthesis was shown to be independent of protein or polyamine synthesis.

Metabolism of NAD in Aspergillus niger. II. Formation of nicotinamide ribose diphosphate ribose, a new metabolite of the NAD pathway, by growing mycelium of Aspergillus niger.

A new step of NAD metabolism was shown in Aspergillus niger. Radioactive nicotinic acid and nicotinamide were incorporated into nicotinamide ribose diphosphate ribose (NAm-RDPR), which had been isolated from the culture filtrate. Its content in the culture medium increased with an increase of culture time, and this compound was proved to be a terminal metabolite in the NAD pathway. The experimental results also showed that the Preiss-Handler pathway and the NAD cycling system function in the NAD biosynthesis in A. niger. A part of the radioactive precursors was also incorporated into an unknown compound.

Metabolism of NAD in Aspergillus niger. I. Formation of nicotinamide ribose diphosphate ribose, a new metabolite of NAD, by Aspergillus niger.

Aspergillus niger (AKU 3302) degraded NAD to form Compound X. This compound was identified as nicotinamide ribose diphosphate ribose (NAmRDPR) by hydrolysis with alkaline or phosphodiesterase followed by chemical analysis of the products. NAmRDPR showed absorption maxima at 265~266 nm in 0.1 n HCI and 325 nm in 1.0 n KCN. Optimal pH for NAmRDPR formation by the enzyme preparation from this organism was around 4.0. Formation of NAmRDPR proceeded stoichiometrically with degradation of NAD. Some of other strains of A. niger formed NAmRDPR, but production of this compound was not demonstrated in other mold genera.

Nuclear Enzymes of NAD Metabolism in Mouse Tissues after Whole-body-X-irradiation

Nuclear Enzymes of NAD Metabolism in Mouse Tissues after Whole-body-X-irradiation

Nicotinamide adenine dinucleotide metabolism in plants. II. Responses of nicotinamide nucleotides to chemical regulators in bean leaves

Incorporation of nicotinic acid-7-14C into nicotinamide adenine dinucleotide by the trifoliate leaves of the bean plant (Phaseolus vulgaris L. var. Brittle Wax) was studied for varying time periods from 5 min to 48 h. Nine radioactive compounds were isolated and identified as all the possible intermediates of NAD metabolism operating in a cyclic pattern. All the intermediates were labelled rapidly and N-methyl nicotinic acid (trigonelline) was detected within 5 min. About 80% of the nicotinic acid fed was accumulated in trigonelline. Senescence induced by floating detached leaves on water enhanced incorporation of the label into nucleotides, NAD > NADP. Treatment with growth regulators altered the NAD/NADP ratios. Benzimidazole and kinetin enhanced NADP synthesis while benzyladenine and ethionine reduced NADP synthesis. The regulator-mediated NADP synthesis is enhanced by light and appears to be inversely related to the synthesis of trigonelline.

The cytotoxicity of chlorambucil and its associated effects on NAD metabolism

Chlorambucil has been reacted with two strains of Yoshida ascites sarcoma cells in vitro and in vivo, and the resultant changes in NAD and NAD-metabolising enzymes related to the quantitative cytotoxicity of the drug at the various doses used. There was no change in the NAD content at any dose up to the LD 100 figure in vivo or in vitro, though supra-lethal concentrations did produce a fall in NAD content in vitro. Curative doses of drug led to increase in the specific activities of NAD glycohydrolase and ATP:NMN adenylyl transferase in vivo, but these were not reflected in changes in the NAD level. Supra-lethal concentrations of the drug produced only small decreases in the levels of these enzymes in vitro. It is concluded that the cytostatic effects of chlorambucil are not mediated through an effect on the intracellular NAD concentration, though at supra-lethal concentrations of the drug a loss of NAD does occur, which may be attributed to non-specific damage to the plasma membrane.

Metabolism of NAD after whole-body irradiation. IV. Incorporation of nicotinamide by isolated perfused liver and by intact rats.

SummaryThe metabolism of nicotinamide was investigated in organs of normal and x-irradiated intact rats (24 h after 1000 R whole-body irradiation) and in isolated perfused rat liver. Rates of reactions were calculated from the data on liver perfusion. At low substrate levels, incorporation of nicotinamide seems to involve pathways via nicotinamide mononucleotide, whereas at high substrate levels the Preiss-Handler pathway via nicotinic acid may play a role. The changes after irradiation are explained as the result of an increased catabolism of NAD which cannot be entirely compensated for by re-synthesis.

Control of DNA replication in Physarum polycephalum: I. Specific activity of NAD pyrophosphorylase in isolated nuclei during the cell cycle

The specific activity of NAD pyrophosphorylase (E.C.2.7.7.1) in isolated nuclei of Physarum polycephalum was estimated throughout the cell cycle. The activity of this enzyme increased between 1 and 1 2 h before mitosis and reached a peak at mitosis. The activity remained high throughout the S phase, which follows mitosis directly in this organism and then declined to a stable, basal level which was maintained throughout the G2 period. This fluctuation in activity is similar to that observed for DNA polymerase and thymidine kinase, but is unlike that of other metabolic enzymes in Physarum. The temporal association of the activity of NAD pyrophosphorylase and DNA synthesis suggests a direct integration of NAD metabolism and DNA biosynthesis.

Nicotinamide adenine dinucleotide metabolism in plants. I. Intermediates of biosynthesis in wheat leaves and the effect of benzimidazole

Leaves of wheat (Triticum aestivum L. var. Selkirk) were incubated with nicotinic acid-7-14C and nicotinamide-7-14C for varying time periods from 5 min to 12 h. Aliquots of alcoholic extracts of leaves were subjected to paper chromatography and radioautography to isolate the intermediates of the synthesis and breakdown of nicotinamide adenine dinucleotide. Nine compounds were isolated quantitatively and identified as intermediates in the pathway of NAD metabolism. All the intermediates were labeled rapidly and the rapidity of labeling became a problem in rigorously proving the sequential operation of the pathway. The results indicate that the Preiss-Handler pathway: nicotinic acid→nicotinic acid mononucleotide→nicotinic acid adenine dinucleotide→NAD operates in wheat leaves. The degradation of NAD proceeded from NAD→nicotinamide mononucleotide→nicotinamide riboside→nicotinamide. Deamidation of the nicotinamide to nicotinic acid initiated a fresh cycle of biosynthesis. The total radioactivity recovered in the intermediates indicates that no measurable amount was lost to other metabolic pathways. Nicotinamide is recovered without significant loss and recycled. The rapid appearance of labeled nicotinamide indicates a possible interconversion of nicotinic acid and nicotinamide. About 80% of the radioactivity accumulated was present in trigonelline which is considered, on the basis of other evidence, to be a non-toxic form of nicotinic acid. Benzimidazole treatment of the leaves increased the incorporation of 14C into NADP.

The synthesis of nicotinamide-adenine dinucleotide and poly (adenosine diphosphate ribose) in various classes of rat liver nuclei.

1. The activities of NMN adenylyltransferase and an enzyme that synthesizes poly (ADP-ribose) from NAD were investigated in the various classes of rat liver nuclei fractionated by zonal centrifugation. 2. The highest specific activities of these two nuclear enzymes occur in different classes of nuclei. In very young and in mature rats it was shown that a correlation exists between DNA synthesis and NMN adenylyltransferase activity, but in rats of intermediate age this correlation is less evident. The highest activities of the enzyme that catalyses formation of poly (ADP-ribose) are in the nuclei involved in the synthesis of RNA. 3. The significance of these results in relation to NAD metabolism is discussed.

Synthesis of NAD and Catabolism of Nicotinic Acid in the Isolated Perfused Liver of Normal and X-irradiated Rat

SummaryThe synthesis of NAD and the formation of catabolites from nicotinic acid 14C was studied in isolated perfused liver from normal and x-irradiated rats. Large amounts of nicotinic acid and nicotinamide increase NAD content of perfused liver as they do in vivo. Synthesis of NAD is slightly diminished after irradiation, particularly under loading conditions whereas its catabolism is enhanced. Data for the rates of reactions are given for different pathways involved in NAD metabolism.