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PubMed1981

Autosomal factors with correlated effects on the activities of the glucose 6-phosphate and 6-phosphogluconate dehydrogenases in Drosophila melanogaster.

Isogenic lines, in which chromosomes sampled from natural populations of C. melanogaster are substituted into a common genetic background, were used to detect and partially characterize autosomal factors that affect the activities of the two pentose phosphate pathway enzymes, glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). The chromosome 3 effects on G6PD and 6PGD are clearly correlated; the chromosome 2 effects, which are not so great, also appear to be correlated, but the evidence in this case is not so strong. Examination of activity variation of ten other enzymes revealed that G6PD and 6PGD are not the only pair of enzymes showing a high positive correlation, but it is among the highest in both sets of lines. In addition, there was some evidence that the factor(s) affecting G6PD and 6PGD may also affect two other metabolically related enzymes, transaldolase and phosphoglucose isomerase.--Rocket immunoelectrophoresis was used to estimate specific CRM levels for three of the enzymes studied: G6PD, 6PGD and ME. This experiment shows that a large part of the activity variation is accounted for by variation in CRM level (especially for chromosome 3 lines), but there remains a significant fraction of the genetic component of activity variation that is not explained by CRM level.--These results suggest that the autosomal factors are modifiers involved in regulation of the expression of the X-linked structural genes for G6PD and 6PGD, but a role in determining part of the enzymes' primary structure cannot be excluded with the present evidence.

Animals↗

PubMed1982

Non-enzymic protein phosphorylation. Phosphorylation of 6-phosphogluconate dehydrogenase by acyl phosphates.

Incubation of 6-phosphogluconate dehydrogenase from Candida utilis with either acetyl phosphate, 1,3-diphosphoglycerate or carbamoyl phosphate results in the phosphorylation of the protein. The binding of one phosphate residue per enzyme subunit does not affect significantly the kinetic properties, but makes the enzyme less reactive toward thiol reagents, trypsin and pyridoxal 5'-phosphate. We suggest indicate that: (1) 6-phosphogluconate dehydrogenase from C. utilis is phosphorylated non-enzymically by physiological acyl phosphates and (2) the phosphorylation of the enzyme modifies the rate of protein inactivation.

Amino Acids↗

PubMed1974

Purification and characterization of the two 6-phosphogluconate dehydrogenase species from Pseudomonas multivorans.

The two species of 6-phosphogluconate dehydrogenase (EC 1.1.1.43) from Pseudomonas multivorans were resolved from extracts of gluconate-grown bacteria and purified to homogeneity. Each enzyme comprised between 0.1 and 0.2% of the total cellular protein. Separation of the two enzymes, one which is specific for nicotinamide adenine dinucleotide phosphate and the other which is active with nicotinamide adenine dinucleotide or nicotinamide adenine dinucleotide phosphate was facilitated by the marked difference in their respective isoelectric points, which were at pH 5.0 and 6.9. Comparison of the subunit compositions of the two enzymes indicated that they do not share common peptide chains. The enzyme active with nicotinamide adenine dinucleotide was composed of two subunits of about 40,000 molecular weight, and the nicotinamide adenine dinucleotide phosphate-specific enzyme was composed of two subunits of about 60,000 molecular weight. Immunological studies indicated that the two enzymes do not share common antigenic determinants. Reduced nicotinamide adenine dinucleotide phosphate strongly inhibited the 6-phosphogluconate dehydrogenase active with nicotinamide adenine dinucleotide by decreasing its affinity for 6-phosphogluconate. Guanosine-5'-triphosphate had a similar influence on the nicotinamide adenine dinucleotide phosphate-specific 6-phosphogluconate dehydrogenase. These results in conjunction with other data indicating that reduced nicotinamide adenine dinucleotide phosphate stimulates the conversion of 6-phosphogluconate to pyruvate by crude bacterial extracts suggest that in P. multivorans, the relative distribution of 6-phosphogluconate into the pentose phosphate and Entner-Doudoroff pathways might be determined by the intracellular concentrations of reduced nicotinamide adenine dinucleotide phosphate and purine nucleotides.

Ammonium Sulfate↗

PubMed1986

Developmental variation in effects of the second and third chromosomes on the activities of the glucose 6-phosphate and 6-phosphogluconate dehydrogenases in Drosophila melanogaster.

Developmental profiles of the second- and third-chromosome modifiers of the activities of glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) in Drosophila melanogaster were investigated. Third-chromosome modifiers showed very strong effects on both enzyme activities at larval, pupal, and adult stages, whereas second-chromosome effects were detected mainly at larval and adult stages. For both enzyme activities and both chromosomes, the correlation over line means between larval and pupal stages was significantly positive, but the correlation between larval or pupal stage and adult stage was not significant. This result suggests that the actions of modifiers on G6PD and 6PGD activities are influenced by the change of developmental stages. Correlation between G6PD and 6PGD activities was positive and highly significant throughout the developmental stages for both sets of chromosomes, although third-chromosome correlations were slightly higher than second-chromosome correlations. The magnitude of the correlation between G6PD and 6PGD activities does not seem to be influenced by the change of development. Diallel crosses for both sets of chromosomes indicate that the action of activity modifiers is mainly additive for both sets of chromosomes, but dominance effects were detected in some cases in adult males. Significant maternal effects were detected for the third chromosome for both enzyme activities until the pupal stage. The change of the activity modifier action after emergence of the imago and the significant correlation between G6PD and 6PGD activities were also detected for diallel progeny.

Animals↗

PubMed1981

Effect of the substrate on the binding of coenzyme and coenzyme analogues to 6-phosphogluconate dehydrogenase from Candida utilis.

6-Phosphogluconate dehydrogenase from Candida utilis is a dimeric enzyme with apparently identical subunits. Two coenzyme analogues, periodate-oxidized NADP+ and 3-amino pyridine adenine dinucleotide phosphate, bind to the protein with Kdiss of 42 microM and 6.2 microM, respectively. NADPH binds to the enzyme with a Kdiss of 0.42 microM. Both coenzyme and coenzyme analogues show "all-of-the sites reactivity." In the presence of the substrate 6-phosphogluconate, the Kdiss of the coenzyme analogues is lowered to 3.5 microM and 2.4 microM, respectively, whereas the Kdiss of NADPH is increased to 2.7 microM. Coenzyme analogues, but not NADPH, show an half of-the sites reactivity in the presence of 6-phosphogluconate. The enzymatic activity is inhibited by high NADP+ concentrations in presence of low concentrations of substrate, whereas at high substrate concentrations no inhibition by NADP+ is showed. These data suggest that: 1) the enzyme exhibits an half-of-the-sites reactivity during the catalytic cycle; 2) the recycle of the enzyme occurs mainly through an abortive ternary complex enzyme-substrate-NADPH.

Candida↗

PubMed1985

Half-site reactivity in 6-phosphogluconate dehydrogenase from human erythrocytes.

6-Phosphogluconate dehydrogenase from human erythrocytes was purified by an improved procedure. Binding studies showed that the dimeric enzyme binds 2 mol of NADP+/mol but only 1 mol of NADPH/mol, and that the bindings of oxidized and reduced coenzyme are mutually exclusive. From initial-rate kinetics and inhibition studies, a sequential random-order mechanism is proposed. Double-reciprocal plots with NADP+ as varied substrate show a downward curvature, indicating a negative co-operativity. We suggest that the negative co-operativity observed kinetically is a result of the half-site reactivity for the NADPH. The different binding stoichiometries for NADP+ and NADPH generate a non-linear relationship between the apparent dissociation constant for the NADPH and the concentrations of the NADP+, resulting in a regulatory mechanism highly sensitive to the changes in the NADP+/NADPH ratio.

Binding Sites↗

PubMed1986

Combined phenotyping of glucose 6-phosphate dehydrogenase (G6PD; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (PDG; EC 1.1.1.44).

The addition of negroid phenotypes to the already heterogeneous population of Israel caused us to reuse the enzymes G6PD and PGD which are known to have a better discrimination power in a negroid population than in caucasians. We have developed a system for combined phenotyping of G6PD and PGD. This system answers the requirements of the above enzymes and results in a negroid population than in caucasians. We have developed a system for combined phenotype-amount of sample and reagents needed and time spent.

Black People↗

PubMed1996

Slow-binding inhibition of 6-phosphogluconate dehydrogenase by zinc ion.

6-Phosphogluconate dehydrogenase (EC 1.1.1.44) has been purified from Cryptococcus neoformans, an encapsulated yeast that is an opportunistic pathogen of AIDS patients. The dimeric enzyme had a subunit molecular weight of 50,000, a specific activity of 50 units mg-1, and Km values of 13 microM for 6-phosphogluconate and 0.89 microM for NADP. This enzyme, like many fungal dehydrogenases, was inhibited by Zn2+, with the inhibition pattern being competitive versus the nonnucleotide substrate. In the presence of micromolar Zn2+, the reaction was biphasic, with the reduction of NADP proceeding initially at the control rate, but, over the time course of 20-300 s, this initial nonlinear phase reached a final, linear steady state with a slower velocity. This pattern is indicative of a slow binding inhibition process, for which we have calculated the following kinetic constants: k6, the limiting rate constant for the transition from initial to final steady state was 0.0024 s-1, corresponding to a half-time of 300 s; Ki*, the overall equilibrium constant for the dissociation of E*Zn2+ to E + Zn2+ was 0.021 microM.

AIDS-Related Opportunistic Infections↗

PubMed1979

Retrograde alteration of 6-phosphogluconate dehydrogenase in axotomized superior cervical ganglia of the rat.

Mechanisms underlying increased activity of 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate: NADP oxidoreductase [decarboxylating] EC 1.1.1.44) in axotomized rat superior cervical ganglia were explored using a highly sensitive micro-immunochemical assay employing antibodies raised in rabbits against the purified enzyme. 6-Phosphogluconate dehydrogenase was purified from rat brain more than 1700-fold by salt fractionation, anion exchange, and immunoaffinity chromatography. The purified enzyme consisted of identical subunits having molecular weights of about 48,800 which could aggregate to catalytically active isomers of various sizes; however, only one form of the enzyme was detected in freshly prepared homogenates of rat neural tissue. Physical and immunological properties of the enzyme from rat brain were similar to those from superior cervical ganglia and liver. Augmented 6-phosphogluconate dehydrogenase activity noted in superior cervical ganglia 2 days after transection of major postganglionic nerve trunks was accompanied by a parallel increase in immunoreactive protein. Michaelis constants of the enzyme were the same in control and axotomized ganglia, and the presence of activators and inhibitors was not detected. It is concluded that increases in 6-phosphogluconate dehydrogenase subsequent to axotomy can be accounted for entirely by an increase in the steady state concentration of this protein.

Animals↗

PubMed2006

Trypanosoma cruzi strains, Tulahuen 2 and Y, besides the difference in resistance to oxidative stress, display differential glucose-6-phosphate and 6-phosphogluconate dehydrogenases activities.

The drugs currently available for Chagas'disease treatment are unsatisfactory due to limited efficacy and toxic side effects, making the search for more specific pharmacological agents a priority. The components of the Trypanosoma cruzi trypanothione-dependent antioxidant system have been pointed out as potential chemotherapeutic targets for the development of more specific drugs. To work properly, this system must have a current supply of NADPH, provided by glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). Here, we compare two T. cruzi strains, Tulahuen 2 and Y, regarding growth rate, cytosolic tryparedoxin peroxidase (TcCPX) concentration and pentose phosphate pathway dehydrogenases activities. Tulahuen 2 cells show higher values as compared to the Y strain when the following parameters are compared: TcCPX concentration, resistance to H2O2, growth index and G6PD activity. Different patterns of G6PD and 6PGD activities were observed among strains along the growth curve and when cells were challenged with H2O2. These data reinforce the heterogeneity within T. cruzi populations and also the importance of G6PD in protecting the parasite against reactive oxygen species.

Animals↗

PubMed1993

Isolation of cDNAs encoding 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase from the mediterranean fruit fly Ceratitis capitata: correlating genetic and physical maps of chromosome 5.

We have isolated and determined the nucleotide sequences for cDNA clones encoding glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) from the medfly Ceratitis capitata. The derived amino acid sequences for G6PD and 6PGD are presented and compared with G6PDs and 6PGDs from other species. The codon usage of the cDNA clones has little bias with the notable exceptions of arginine, glycine and leucine. The chromosomal location of the genes for 6PGD and G6PD were determined by in situ hybridization to salivary gland polytene chromosomes. This localization orients a genetic map of enzymatic loci and illustrates a remarkable similarity in the intra chromosomal order of homologous genes between Drosophila melanogaster and medfly.

Amino Acid Sequence↗

PubMed1976

Specific activities of 6-phosphogluconate dehydrogenase, glucose-6-phosphate dehydrogenase and glucose-6-phosphate isomerase during Bufo bufo development.

It has been suggested by some authors that during amphibian development, due to the higher glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activity compared to that of 6-phosphogluconate dehydrogenase (EC 1.1.1.43), 6-phosphogluconate could accumulate in the embryo tissues and regulate the channelling of glucose-6-phosphate into glycolysis. Here, on the base of the specific activities of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and glucose-6-phosphate isomerase (EC 5.3.1.9) found in the embryos of Bufo bufo during development, it is discussed whether 6-phosphogluconate can accumulate and play a regulative role on glucose-6-phosphate metabolism in the anuran embryo.

Animals↗

PubMed1990

Altered growth-rate-dependent regulation of 6-phosphogluconate dehydrogenase level in hisT mutants of Salmonella typhimurium and Escherichia coli.

In Escherichia coli, the level of 6-phosphogluconate dehydrogenase is directly proportional to the cellular growth rate during growth in minimal media. This contrasts with the report by Winkler et al. (M. E. Winkler, J. R. Roth, and P. E. Hartman, J. Bacteriol. 133:830-843, 1978) that the level of the enzyme in Salmonella typhimurium LT-2 strain SB3436 is invariant. The basis for the difference in the growth-rate-dependent regulation between the two genera was investigated. Expression of gnd, which encodes 6-phosphogluconate dehydrogenase, was growth rate uninducible in strain SB3436, as reported previously, but it was 1.4-fold growth rate inducible in other S. typhimurium LT-2 strains, e.g., SA535. Both the SB3436 and SA535 gnd genes were growth rate inducible in E. coli K-12. Moreover, the nucleotide sequences of the regulatory regions of the two S. typhimurium genes were identical. We concluded that a mutation unlinked to gnd is responsible for the altered growth rate inducibility of 6-phosphogluconate dehydrogenase in strain SB3436. Transductional analysis showed that the altered regulation is due to the presence of a mutation in hisT, the gene for the tRNA modification enzyme pseudouridine synthetase I. A complementation test showed that the regulatory defect conferred by the hisT mutation was recessive. In E. coli, hisT mutations reduced the extent of growth rate induction by the same factor as in S. typhimurium. The altered regulation conferred by hisT mutations was not simply due to their general effect of reducing the polypeptide chain elongation rate, because miaA mutants, which lack another tRNA modification and have a similarity reduced chain growth rate, had higher rather than lower 6-phosphogluconate dehydrogenase levels. Studies with genetic fusions suggested that hisT mutations lower the gnd mRNA level. The data also indicated that hisT is involved in translational control of gnd expression, but not the aspect mediated by the internal complementary sequence.

Cloning, Molecular↗

PubMed1992

Purification and characterization of cytosolic 6-phosphogluconate dehydrogenase isozymes from maize.

Cytosolic isozymes of 6-phosphogluconate dehydrogenase were purified from roots of maize (Zea mays L.). The final preparation contained two 55-kD proteins. Affinity-purified dehydrogenases from a maize line that is null for both cytosolic 6-phosphogluconate dehydrogenase isozymes (Pgd1-null, Pgd2-null) lacked the 55-kD proteins. The substrate kinetics of the purified enzyme were determined.

Journal Article↗

PubMed1981

Substrate-induced intramolecular proton transfer in 6-phosphogluconate dehydrogenase from Candida utilis.

Formation of binary complex between 6-phosphogluconate dehydrogenase (6-phospho-D-gluconate:NADP+ 2-oxidoreductase (decarboxylating), EC 1.1.1.44) from Candida utilis and 6-phosphogluconate was investigated by means of ultraviolet difference spectroscopy. The formation of the enzyme-substrate complex induces in the difference spectrum a positive peak the wavelength and extinction coefficient of which agree well with a tyrosine ionization. Titrimetric studies indicate that the formation of the binary complex is not coupled to a proton release from the protein. These data support an intramolecular proton transfer from a tyrosine to other functional group. This proton transfer could be correlated to the conformational change induced by substrate in 6-phosphogluconate dehydrogenase.

Candida↗

PubMed1975

Human granulocyte 6 phosphogluconate dehydrogenase. Purification by elective elution with NADP+, immunological and kinetic properties.

Human granulocyte 6 phosphogluconate dehydrogenase has been totally purified from a single patient with chronic granulocytic leukaemia. 48 mg of protein, of specific activity 20 IU per mg of protein, have been obtained in the course of three different steps only. The overall yield was 30 p. cent and the purification was 100 folds. Purified 6 phosphogluconate dehydrogenase was homogeneous when tested in acrylamide and acrylamide SDS gel electrophoresis or in immunodiffusion. The enzyme was immunologically identical in red blood cells, blood platelets and normal leukocytes. The fixation of both substrates, NADP-+ and 6 phosphogluconate, seemed to proceed through a non ordered mechanism. NADPH was an inhibitor strictly competitive with respect to NADP-+ and non competitive with respect to 6 phosphogluconate. 2-3 Diphosphoglycerate seemed to be able to bind on both the fixation sites of NADP-+ and 6 phosphogluconate. The inhibition by ATP was competitive with 6 phosphogluconate and non competitive with NADP-+. 6 phosphogluconate dehydrogenase was inactivated by SH reagents and was partially protected against this inactivation by both substrates. Both substrates protected the enzyme against thermal inactivation. The influence of ionic strength, pH and ions have been studied, and the results have been compared to those reported by other authors for erythrocyte enzyme.

Adenosine Triphosphate↗

PubMed2004

Effects of some antibiotics on human erythrocyte 6-phosphogluconate dehydrogenase: an in vitro and in vivo study.

The in vitro and in vivo effects of some antibiotics on human erythrocyte 6-phosphogluconate dehydrogenase were investigated. Human erythrocyte 6-phosphogluconate dehydrogenase was purified with ammonium sulphate precipitation, 2',5' ADP-Sepharose 4B affinity and gel filtration chromatography. Some antibiotics (netilmicin sulphate, cefepime, amikacin, isepamycin, chloramphenicol, ceftazidim, teicoplanin, ampicillin, ofloxacin, levofloxacin, cefotaxime, penicillin G, gentamicin sulphate, ciprofloxacin) inhibited enzyme activity in vitro but others (cefozin, decefin, streptomycin, combisid, and meronem) were devoid of inhibitory effects. For the drugs having low IC50 values (netilmicin sulphate and cefepime), in vivo studies were performed in rats. Netilmicin sulphate at 15-mg/kg inhibited enzyme activity significantly (p < 0.001) 1 h, 2 h, and 3 h after dosing and cefepime at 200-mg/kg very significantly (p < 0.001) inhibited the enzyme 1 h and 2 h after dosing. Netilmicin sulphate and cefepime inhibited rat erythrocyte 6-phosphogluconate dehydrogenase both in vivo and in-vitro.

Animals↗

PubMed2005

Circadian variations in the activities of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase in the liver of control and streptozotocin-induced diabetic rats.

The aim of this study was to examine: the 24 h variation of 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase activities, key enzymes for the maintenance of intracellular NADPH concentration, in rat liver in control and streptozotocin-induced diabetic animals. Adult male rats were fed ad libitum and synchronized on a 12:12 h light-dark cycle (lights on 08:00 h). One group of animals was treated with streptozotocin (STZ, 55 mg/kg, intraperitoneal) to induce experimental diabetes. Eight weeks after STZ injection, the animals were sacrificed at six different times of day--1, 5, 9, 13, 17 and 21 Hours After Lights On (HALO)--and livers were obtained. Enzyme activities were determined spectrophotometrically in triplicate in liver homogenates and expressed as units per mg protein. 6-phosphogluconate dehydrogenase activity was measured by substituting 6-phosphogluconate as substrate. Glucose-6-phosphate dehydrogenase activity was determined by monitoring NADPH production. Treatment, circadian time, and interaction between treatment and circadian time factors were tested by either one or two way analysis of variance (ANOVA). Two-way ANOVA revealed that 6-phosphogluconate dehydrogenase activity significantly depended on both the treatment and time of sacrifice. 6-phosphogluconate dehydrogenase activity was higher in control than diabetic animals; whereas, glucose-6-phosphate dehydrogenase activity did not vary over the 24 h in animals made diabetic by STZ treatment. Circadian variation in the activity of 6-phosphogluconate dehydrogenase was also detected in both the control and STZ treatment groups (one-way ANOVA). Time-dependent variation in glucose-6-phosphate dehydrogenase activity during the 24 h was detected in control but not in diabetic rats. No significant interaction was detected between STZ-treatment and time of sacrifice for both hepatic enzyme activities. These results suggest that the activities of NADPH-generating enzymes exhibit 24 h variation, which is not influenced by diabetes.

Animals↗