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.     

Primate red cell enzymes: glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase

Glucose-6-phosphate dehydrogenase (E. C.: 1.1.1.49) phenotypes and 6-phosphogluconate dehydrogenase (E. C.: 1.1.1.44) phenotypes were determined by starch-gel electrophoresis of red cell hemolysates of Galago crassicaudatus subspp., Propithecus verreauxi, Lemur spp., Hapalemur griseus, and Macaca mulatta. A single glucose-6-phosphate dehydrogenase (G6PD) phenotype was found in each species. A single 6-phosphogluconate dehydrogenase (6PGD) phenotype was found in Lemur spp., Hapalemur griseus, and Galago crassicaudatus argentatus. In a group of six Propithecus verreauxi, three 6PGD phenotypes, PGD A, PGD AB, and PGD B, were found. Three phenotypes, PGD A, PGD AB, and PGD B, were found in 38 G. c. crassicaudatus. The three phenotypes in each species are apparently the products of two codominant autosomal alleles, PGD^A and PGD^B. The frequency of PGD^A in G. c. crassicaudatus is 0.263. A population of 260 free-ranging macaques displays a polymorphism at the 6PGD locus. Three phenotypes, PGD A, PGD AB, and PGD B, were found. These also appear to be controlled by two codominant autosomal alleles, PGD^A and PGD^B the frequency of PGD^A = 0.913. Additional analysis of three well-defined troops within the macaque population indicated that there are no significant differences between the troops or within the population at the 6PGD locus.     

Effectors of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of rat liver.

Summary The lower Vmax of 6PGDH with respect to G6PDH and its higher sensitivity to inhibition by NADPH, suggest the existence of an imbalance between the two dehydrogenases of the pentose phosphate pathway in rat liver. Possible modulators of these activities, particularly in relation with the inhibition by NADPH in physiological conditions, have been investigated. The results suggest that in both cases the inhibition by NADPH is strictly isosteric and that the relative affinities for the reduced and oxidized forms of the pyridine nucleotide are unaffected by glutathion, the intermediates of the pentose phosphate shunt or some divalent ions.Abbreviations G6PDH glucose-6-phosphate dehydrogenase (EC 1.1.1.49) - 6PGDH 6-phosphogluconate dehydrogenase (EC 1.1.1.44) On leave from the Instituto de Bioquímica, Facultad de Ciencias, Universidad Austral de Chile, Casilla 567, Valdivia, Chile.     

Two isoenzymes each of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in spinach leaves

Isoenzymes of glucose-6-phosphate dehydrogenase and 6-P-gluconate dehydrogenase from a 70% ammonium sulfate precipitate of spinach leaf homogenate were separated by differential solubilization in a gradient of 70-0% ammonium sulfate and analyzed by disc gel electrophoresis. Isolated whole chloroplasts contained isoenzyme 1 of both glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase 1, whereas isoenzyme 2 of each was found in the soluble cytosol fraction. Both isoenzymes of each dehydrogenase were present in about equal amounts. Glucose-6-phosphate dehydrogenase isoenzymes 1 and 2 had pH optima of 9.2 and 9.0 and K_m values of 400 and 330 μm, respectively. Molecular weights for both isoenzyme of glucose-6-phosphate dehydrogenase were very similar at about 105,000 ± 10% as estimated by sedimentation velocity measurements. For 6-phosphogluconate dehydrogenase isoenzymes 1 and 2 the pH optima were 9.0 and 9.3, respectively, the K_m values were 100 and 80 μm, and the apparent molecular weights were also nearly identical at about 110,000 ± 10%. The data support the hypothesis that leaf cells have two oxidative pentose phosphate pathways, one in the chloroplast and the other in the cytosol.     

Regulation of specific activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in Penicillium chrysogenum

Abstract The specific activity of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase changed when Penicillium chrysogenum was grown on different carbon sources. In the presence of 2% lactose, the activities of these enzymes were approximately 25–35% lower than those in media containing 2% glucose or 2% fructose. We assume that an increase in cAMP concentration was responsible for the observed decreases in the enzyme activities, because a higher cAMP concentration could be detected when the mycelium was grown in a medium containing solely lactose as carbon source. The likely role played by cAMP in the regulation was also demonstrated by the addition of either cAMP or caffeine to the medium.     

Maternal effect for genes encoding 6-phosphogluconate dehydrogenase and glucose-6-phosphate dehydrogenase in Drosophila melanogaster

We studied the maternal effect for two enzymes of the pentose cycle, 6-phosphogluconate dehydrogenase (6PGD) and glucose-6-phosphate dehydrogenase (G6PD), using a genetic system based on the interaction of Pgd^? and Zw^? alleles, which inactivate 6PGD and G6PD, respectively. The presence and formation of the enzymes was investigated in those individuals that had not received the corresponding genes from the mother. We revealed maternal forms of the enzymes, detectable up to the pupal stage. The activities of “maternal” 6PGD and G6PD per individual increased 20-fold to 30-fold from the egg stage to the 3rd larval instar even in the absence of normal Pgd and Zw genes. Immunologic studies have shown that the increase in 6PGD activity is due to an accumulation of the maternal form of the enzyme molecules. We revealed a hybrid isozyme resulting from an aggregation of the subunits of isozymes controlled by the genes of the mother and embryo itself. These results indicate that the maternal effect in the case of 6PGD is due to a long-lived stable mRNA transmitted with the egg cytoplasm and translated during the development of Drosophila melanogaster.     

Enzyme patterns in D. melanogaster imaginal discs: distribution of glucose-6-phosphate and 6-phosphogluconate dehydrogenase

Distribution of glucose-6-phosphate dehydrogenase (G6PD) and 6-phospho-gluconate dehydrogenase (6PGD) in imaginal discs of Drosophila melanogaster was determined. Differential patterns of staining were found in all discs examined, i.e., eye-antennal, wing, leg, labial and genital. By using null mutants for either G6PD or 6PGD, the enzymes were shown to have the same distribution patterns. Staining with glucose-6-phosphate as a substrate resulted in the detection of both G6PD and 6PGD. Results of staining discs from homoeotic mutants indicate that the enzyme distribution patterns are under genetic control. In the presence of the homoeotic engrailed (en) mutation which transforms posterior wing compartment into anterior, the G6PD pattern of the posterior compartment of the wing disc was specifically transformed toward that of the anterior compartment. The bithorax series of homoeotic mutants was similarly investigated. The bithorax (bx3) mutation transforms the anterior part of the haltere to anterior wing blade. Similarly the G6PD pattern in the anterior haltere disc transforms to that of anterior wing disc. The complimentary transformation, postbithorax (pbx) results in a change of the posterior part of the haltere to posterior wing, which is likewise reflected in an altered staining pattern for G6PD in the posterior portion of the haltere disc. The combination of the bx3 and pbx resulted in a staining pattern of the haltere disc virtually indistinguishable from the normal wing disc.     

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.     

Effects of insulin on the adaptation of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in rat adipose tissue

1.

1. The effects of insulin on adipose tissue glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were studied.     

Apparent unbalance between the activities of 6-phosphogluconate and glucose-6-phosphate dehydrogenases in rat liver

The ratio of activities of 6-phosphogluconate dehydrogenase/glucose-6-phosphate dehydrogenase measured in liver extracts of rats in lipogenic nutritional conditions is only 0.2, suggesting an apparent physiological unbalance between the two dehydrogenases of the hexosemonophosphate shunt. This potential unbalance is enhanced by the fact that TPNH is a more powerful competitive inhibitor of 6-phosphogluconate dehydrogenase than of glucose-6-phosphate dehydrogenase. Accordingly, a strong activation of 6-phosphogluconate dehydrogenase would be required for efficient functioning of this pathway, unless there is an alternative outlet for 6-phosphogluconate so far unrecognized in animal tissues.     

Purification and properties of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase from a methanol-utilizing yeast,Candida boidinii

Glucose-6-phosphate dehydrogenase (d-glucose-6-phosphate: NADP oxidoreductase, EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6-phospho-d-gluconate: NADP oxidoreductase, EC 1.1.1.44) were purified approx. 1700 fold and 330 fold, respectively, from Candida boidinii grown on methanol. The final enzyme preparations were homogeneous as judged by polyacrylamide gel electrophoresis. The molecular weights of the enzymes were estimated to be 118 000 and 110 000, respectively. Both enzymes are composed of two probably identical subunits and the molecular weights of the polypeptide chains were calculated to be 61 000 and 58 000, respectively.From a consideration of enzyme activities and types of inhibition by different metabolites the role of these two enzymes in glucose- and methanol-metabolism is discussed.     

Dosage compensation of sex-linked genes in Drosophila melanogaster. The activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in flies with normal and disturbed genetic balance

Summary The phenomenon of dosage compensation in Drosophila melanogaster which consists in doubling of the activity of the X-chromosome genes in males as compared to those in females was studied.The specific activities of 6-phosphogluconate dehydrogenase (6PGD) and glucose-6-phosphate dehydrogenase (G6PD) determined by the sex-linked structural genes Pgd and Zw respectively were studied in flies carrying duplications for different regions of the X-chromosome. The increase in dose of Pgd and Zw in females resulting from the addition of an extra X-chromosome or X-fragments leads to a proportional rise in the specific activities of 6PGD and G6PD. On the other had the addition to females of the X-chromosome carrying no Pgd gene or X-fragments lacking Pgd and Zw has no effect on the enzyme activities. Thus we failed to reveal in the X-chromosome any compensatory genes envisaged by Muller, which would repress sex-linked structural genes proportional to their dose.The 6PGD and G6PD levels in phenotypically male-like intersexes carrying two X-chromosomes and three autosome sets (2X3A) is 30% higher than in diploid (2X2A) or triploid (3X3A) females. However the specific activities of the enzymes in female-like intersexes are the same as in regular females. The levels of 6PGD and G6PD per one X-chromosome are 1.5–2.0 times higher in the intersexes than in the normal females and metafemales (3X2A). The results indicate that the level of expression of the X-chromosome is determined by the X:A ratio. It is suggested that the decreased X:A ratio in males is responsible for the hyperactivation of their X-chromosomes.     

X-linked glucose-6-phosphate dehydrogenase (G6PD) and autosomal 6-phosphogluconate dehydrogenase (6PGD) polymorphisms in baboons

Electrophoretic polymorphisms of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) were examined in captive colonies of five subspecies of baboons (Papio hamadryas). Phenotype frequencies and family data verified the X-linked inheritance of the G6PD polymorphism. Insufficient family data were available to confirm autosomal inheritance of the 6PGD polymorphism, but the electrophoretic patterns of variant types (putative heterozygotes) suggested the codominant expression of alleles at an autosomal locus. Implications of the G6PD polymorphism are discussed with regard to its utility as a marker system for research on X-chromosome inactivation during baboon development and for studies of clonal cell proliferation and/or cell selection during the development of atherosclerotic lesions in the baboon model.     

Selective precipitation of phosphofructokinase,glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase from rat erythrocyte hemolysates by polyethylene glycol

Precipitation profiles of phosphofructokinase, glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase have been established in the range of 0–16% PEG at different pH (5–7) values. Precipitation generally occurred between narrow limits of polyethylene glycol. The polymer concentration needed to reach any level of enzyme precipitation is dependent on pH. Particular conditions (% PEG and pH) for the selective enzyme enrichment have been determined.