NAD-glutamate Dehydrogenase Research Articles

NADP-Specific glutamate dehydrogenase in Metridium senile (L.)

1. 1. An NADP-specitic glutamate dehydrogenase (E.C. 1.4.1.4) of mitochondrial origin has been detected in M. senile, a sea anemone. 2. 2. Substrate specificity and starch gel electrophoresis experiments indicated an absence of the NAD(P) glutamate dehydrogenase (E.C. 1.4.1.3). 3. 3. This NADP specific GDH activity appears to be the sole GDH activity in species of the animal phylum Coelenterata.

The synthesis of yeast matrix mitochondrial enzymes is regulated by different levels of mitochondrial function

The role of mitochondria in the oxygen induction of a number of catabolic and mitochondrial enzymes (citrate synthase, NAD- and NADP-isocitrate dehydrogenases, oxoglutarate dehydrogenase, NAD-glutamate dehydrogenase) has been investigated in anaerobic yeast grown under different conditions. The patterns of variation of enzyme activity with oxygen and lipid content of the mitochondria and with antibiotics suggest that more than one control is operating. The inhibition produced by cycloheximide, which blocks protein translation, suggests that induction involves de novo protein synthesis, except for an initial 2-h induction of citrate synthase, which is insensitive to all antibiotics tested. Ethidium bromide prevents enzyme induction in lipid-depleted anaerobic yeast. Induction follows normal kinetics in lipid-supplemented cultures despite the ethidium bromide block in the development of respiratory ability. Enzyme induction is inhibited by chloramphenicol in both lipid-depleted and lipid-supplemented anaerobic yeast. On the basis of four results it can be postulated that the mitochondrial genome is involved in controlling the induction of enzymes synthesized on cytoplasmic ribosomes. This control might be exerted by a specific, mitochondrial product or might be the result of modulation by a secondary product of mitochondrial function.

NAD and NADP l-glutamate dehydrogenase activity and ammonium regulation in Aspergillus nidulans.

Summary: Mutants, designated gdhA, deficient in NADP-glutamate dehydrogenase activity grow poorly using inorganic nitrogen but normally using amino acids as nitrogen sources. The gdhA mutants are not repressed by ammonia for a number of enzyme and uptake systems. The nine gdhA mutations are allelic and located in linkage group III; gdhAi is recessive in the heterozygous diploid with respect to both NADP glutamate dehydrogenase activity and ammonium regulation. Mutants, designated gdhB, deficient in NAD-glutamate dehydrogenase activity are unable to utilize l-glutamate as a carbon source, but can utilize inorganic and organic nitrogen as nitrogen sources. The four gdhB mutations are allelic, located in linkage group IV, and gdhBI is recessive in the heterozygous diploid. The gdhB mutants are repressed for the ammonium regulated systems which are not repressed in gdhA mutants.

Release of the “ammonia effect” on three catabolic enzymes by NADP-specific glutamate dehydrogenaseless mutations in [formula omitted

Mutations which inactivate the NADP-glutamate dehydrogenase (anabolic GDHase) pleiotropically release the ammonia inhibition (NH 4 + effect) on a number of distinct catabolic activities. In addition to releasing inhibition on several permeability functions (1), these mutations suppress the NH 4 + effect on the synthesis of arginase, urea amidolyase and allantoinase. They do not affect the NH 4 + effect on the NAD-glutamate dehydrogenase. Two mechanisms of action of these mutations have to be considered, namely a modification of the process of induction (such as removal of inducer exclusion) and a suppression of nitrogen catabolite repression .

Intracellular location of nitrate reductase and nitrite reductase. II. Wheat roots

Approximately 15% of the total nitrite reductase of crude homogenates of wheat roots applied to sucrose gradients was separated with an organelle whose isopycnic density was about 1.22 g·cm −3. The activity recovered in the supernatant was thought to be particulate in origin, because similar ratios of activity of isoenzyme 1 and 2 of nitrite reductase were found in both particulate and supernatant fractions. The particle with nitrite reductase activity also contained glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, triose phosphate isomerase and NADPH diaphorase. This root particle and whole chloroplasts from leaves had a similar isopycnic density as well as these enzymes, and thus the data suggest that the root particle may be a proplastid. Nitrate reductase was found only in the supernatant and it was not associated with any of the root organelles. Mitochondria from wheat roots had an equilibrium density of 1.18 g·cm −3 and contained both NAD and NADP glutamate dehydrogenase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, triosephosphate isomerase and NADPH diaphorase but not nitrite reductase. Microbodies of wheat roots had an equilibrium density of about 1.20 g·cm −3 on the sucrose gradient and contained catalase and glycollate oxidase.

Pathway of carbon flow during fatty acid synthesis from lactate and pyruvate in rat adipose tissue

The metabolism of pyruvate and lactate by rat adipose tissue was studied. Pyruvate and lactate conversion to fatty acids is strongly concentration-dependent. Lactate can be used to an appreciable extent only by adipose tissue from fasted-refed rats. A number of compounds, including glucose, pyruvate, aspartate, propionate, and butyrate, stimulated lactate conversion to fatty acids. Based on studies of incorporation of lactate-2-(3)H and lactate-2-(14)C into fatty acids it was suggested that the transhydrogenation sequence of the "citrate-malate cycle"(1) was not providing all of the NADPH required for fatty acid synthesis from lactate. An alternative pathway for NADPH formation involving the conversion of isocitrate to alpha-ketoglutarate via cytosolic isocitrate dehydrogenase was proposed. Indirect support for this proposal was provided by the rapid labeling of glutamate from lactate-2-(14)C by adipose tissue incubated in vitro, as well as the demonstration that glutamate can be readily metabolized by adipose tissue via reactions localized largely in the cytosol. Furthermore, isolated adipose tissue mitochondria convert alpha-ketoglutarate to malate, or in the presence of added pyruvate, to citrate. Glutamate itself can not be metabolized by these mitochondria, a finding in keeping with the demonstration of negligible levels of NAD-glutamate dehydrogenase activity in adipose tissue mitochondria. Pyruvate stimulated alpha-ketoglutarate and malate conversion to citrate and reduced their oxidation to CO(2). It is proposed that under conditions of excess generation of NADH malate may act as a shuttle carrying reducing equivalents across the mitochondrial membrane. Malate at low concentrations increased pyruvate conversion $$Word$$ citrate and markedly decreased the formation of CO(2) by isolated adipose tissue mitochondria. Malate also stimulated citrate and isocitrate metabolism by these mitochondria, an effect that could be blocked by 2-n-butylmalonate. This potentially important role of malate in the regulation of carbon flow during lipogenesis is underlined by the observation that 2-n-butylmalonate inhibited fatty acid synthesis from pyruvate, but not from glucose and acetate, and decreased the stimulatory effect of pyruvate on acetate conversion to fatty acids.

Effect of nitrogen source on glutamate dehydrogenase and alanine dehydrogenase of Chlorella

During nitrogen assimilation by Chlorella a change in the source of this element produced a substantial effect on the activity of NADP-glutamate dehydrogenase and a smaller effect on the activity of alanine dehydrogenase. The activity of NAD-glutamate dehydrogenase was almost unaffected. NADP-glutamate dehydrogenase activity drastically increased upon cultivation on ammonium salts and decreased upon cultivation on nitrate. These changes resulted from an enhancement or reduction of the synthesis of enzymic protein. Glutamine, alanine, and α-ketoglutarate exerted no effect on the activity of the tested enzymes.

NAD and NADP-dependent glutamate dehydrogenase in Hydrogenomonas H 16.

Hydrogenomonas H 16 synthetized two chromatographically distinct forms of glutamate dehydrogenase which differed in their thermolability. One glutamate dehydrogenase utilized NAD, the other NADP as a coenzyme.

Enzyme histochemistry of the adult liver fluke, Fasciola hepatica

The distribution of seventeen enzyme systems has been investigated histochemically in the adult liver fluke, Fasciola hepatica. The enzymes studied were NAD diaphorase, NADP diaphorase, succinic dehydrogenase, glucose-6-phosphate dehydrogenase, malate dehydrogenase, isocitrate dehydrogenase, lactate dehydrogenase, glutamate dehydrogenase, α-glycerophosphate dehydrogenase, β-hydroxybutyrate dehydrogenase, acid phosphatase, alkaline phosphatase, glucose-6-phosphatase, esterase, adenosine triphosphatase, 5-nucleotidase, and cytochrome oxidase. Only two enzymes, β-hydroxybutyrate dehydrogenase and 5-nucleotidase, were entirely absent. Three enzymes of the tricarboxylic acid cycle in the fluke were shown to be present. Although the tegument has been thought to be responsible for absorption of food and excretion of waste materials, the gut is better equipped enzymatically for these functions. The small amount of glucose-6-phosphatase and the complete absence of β-hydroxybutyrate dehydrogenase is explained by the abundance of glycogen present in the fluke, which is probably supplied by the liver of the host animal. Despite the predominantly anaerobic nature of the respiration, cytochrome oxidase activity was detected in the fluke.

Studien zur oscillation der synthesegeschwindigkeit von nad-abhängiger glutamatdehydrogenase in Saccharomyces cerevisiae

1. 1. Further data on oscillatory phenomena in the rate of enzyme synthesis of NAD-dependent glutamate dehydrogenase ( l-glutamate:NAD + oxidoreductase (deaminating), EC 1.4.1.2) in Saccharomyces cerevisiae during derepression by transfer from an NH 4 +-containing medium to a glutamate medium are reported. The growth rate of the cells indicates a high intracellular level of NH 4 + when the enzyme reaches maximum activity in the course of an oscillation. This causes repression, whereby a new period of oscillation is started. Synchronous growth as the reason for the oscillations is excluded. 2. 2. Glutamine synthetase (EC 6.3.1.2), whose rate of synthesis is also influenced by NH 4 +, shows different kinetics of derepression from NAD-glutamate dehydrogenase. Enzymes whose syntheses are not controlled by NH 4 + ( viz. NADP-glutamate dehydrogenase (EC 1.4.1.4), glucose-6-phosphate dehydrogenase (EC 1.1.1.49) show no rhythmic changes in the rate of their syntheses. 3. 3. Further evidence is presented for the function of NH 4 + as the corepressor of NAD-dependent glutamate dehydrogenase. The final level to which the specific activity of this enzyme is adjusted during derepression is controlled by the velocity of NH 4 + formation from glutamate in the cells.