Two distinct glyceraldehyde-3-phosphate dehydrogenases in glycolysis and gluconeogenesis in the archaeon Haloferax volcanii.

The halophilic archaeon Haloferax volcanii degrades glucose via the semiphosphorylative Entner-Doudoroff pathway and can also grow on gluconeogenic substrates. Here, the enzymes catalysing the conversion of glyceraldehyde-3-phosphate (GAP) to 3-phosphoglycerate were analysed. The genome contains the genes gapI and gapII encoding two putative GAP dehydrogenases, and pgk encoding phosphoglycerate kinase (PGK). We show that gapI is functionally involved in sugar catabolism, whereas gapII is involved in gluconeogenesis. For pgk, an amphibolic function is indicated. This is the first report of the functional involvement of a phosphorylating glyceraldehyde-3-phosphate dehydrogenase and PGK in sugar catabolism in archaea. Phylogenetic analyses indicate that the catabolic gapI from H. volcanii is acquired from bacteria via lateral genetransfer, whereas the anabolic gapII as well as pgk are of archaeal origin.

The Multiple Localized Glyceraldehyde-3-Phosphate Dehydrogenase Contributes to the Attenuation of the Francisella tularensis dsbA Deletion Mutant.

The DsbA homolog of Francisella tularensis was previously demonstrated to be required for intracellular replication and animal death. Disruption of the dsbA gene leads to a pleiotropic phenotype that could indirectly affect a number of different cellular pathways. To reveal the broad effects of DsbA, we compared fractions enriched in membrane proteins of the wild-type FSC200 strain with the dsbA deletion strain using a SILAC-based quantitative proteomic analysis. This analysis enabled identification of 63 proteins with significantly altered amounts in the dsbA mutant strain compared to the wild-type strain. These proteins comprise a quite heterogeneous group including hypothetical proteins, proteins associated with membrane structures, and potential secreted proteins. Many of them are known to be associated with F. tularensis virulence. Several proteins were selected for further studies focused on their potential role in tularemia's pathogenesis. Of them, only the gene encoding glyceraldehyde-3-phosphate dehydrogenase, an enzyme of glycolytic pathway, was found to be important for full virulence manifestations both in vivo and in vitro. We next created a viable mutant strain with deleted gapA gene and analyzed its phenotype. The gapA mutant is characterized by reduced virulence in mice, defective replication inside macrophages, and its ability to induce a protective immune response against systemic challenge with parental wild-type strain. We also demonstrate the multiple localization sites of this protein: In addition to within the cytosol, it was found on the cell surface, outside the cells, and in the culture medium. Recombinant GapA was successfully obtained, and it was shown that it binds host extracellular serum proteins like plasminogen, fibrinogen, and fibronectin.

Exploring the genetic control of glycolytic oscillations in Saccharomyces cerevisiae.

BACKGROUND: A well known example of oscillatory phenomena is the transient oscillations of glycolytic intermediates in Saccharomyces cerevisiae, their regulation being predominantly investigated by mathematical modeling. To our knowledge there has not been a genetic approach to elucidate the regulatory role of the different enzymes of the glycolytic pathway. RESULTS: We report that the laboratory strain BY4743 could also be used to investigate this oscillatory phenomenon, which traditionally has been studied using S. cerevisiae X2180. This has enabled us to employ existing isogenic deletion mutants and dissect the roles of isoforms, or subunits of key glycolytic enzymes in glycolytic oscillations. We demonstrate that deletion of TDH3 but not TDH2 and TDH1 (encoding glyceraldehyde-3-phosphate dehydrogenase: GAPDH) abolishes NADH oscillations. While deletion of each of the hexokinase (HK) encoding genes (HXK1 and HXK2) leads to oscillations that are longer lasting with lower amplitude, the effect of HXK2 deletion on the duration of the oscillations is stronger than that of HXK1. Most importantly our results show that the presence of beta (Pfk2) but not that of alpha subunits (Pfk1) of the hetero-octameric enzyme phosphofructokinase (PFK) is necessary to achieve these oscillations. Furthermore, we report that the cAMP-mediated PKA pathway (via some of its components responsible for feedback down-regulation) modulates the activity of glycoytic enzymes thus affecting oscillations. Deletion of both PDE2 (encoding a high affinity cAMP-phosphodiesterase) and IRA2 (encoding a GTPase activating protein- Ras-GAP, responsible for inactivating Ras-GTP) abolished glycolytic oscillations. CONCLUSIONS: The genetic approach to characterising the glycolytic oscillations in yeast has demonstrated differential roles of the two types of subunits of PFK, and the isoforms of GAPDH and HK. Furthermore, it has shown that PDE2 and IRA2, encoding components of the cAMP pathway responsible for negative feedback regulation of PKA, are required for glycolytic oscillations, suggesting an enticing link between these cAMP pathway components and the glycolysis pathway enzymes shown to have the greatest role in glycolytic oscillation. This study suggests that a systematic genetic approach combined with mathematical modelling can advance the study of oscillatory phenomena.

Oxidation of glyceraldehyde-3-phosphate dehydrogenase decreases sperm motility.

The relation between the activity of the sperm-specific glyceraldehyde-3-phosphate dehydrogenase (GAPDS) and the motility of sperms was investigated. It was found that the mean value of GAPDS activity in sperm samples with low motility is 2.5-3-fold lower than that in samples with high motility. Sperm motility was shown to diminish in the presence of superoxide anion, hydroxyl radical, and hydrogen peroxide. The decrease in sperm motility in the presence of hydrogen peroxide was proportional to the concentration of the oxidant and correlated with the decrease in GAPDS activity (r = 0.96). Based on the literature data on the importance of GAPDS for the motility of sperms together with the presented observations, it was concluded that the decrease in the sperm motility in the presence of reactive oxygen species is due to the oxidation of GAPDS and inhibition of glycolysis.

Arabidopsis plants deficient in plastidial glyceraldehyde-3-phosphate dehydrogenase show alterations in abscisic acid (ABA) signal transduction: interaction between ABA and primary metabolism.

Abscisic acid (ABA) controls plant development and regulates plant responses to environmental stresses. A role for ABA in sugar regulation of plant development has also been well documented although the molecular mechanisms connecting the hormone with sugar signal transduction pathways are not well understood. In this work it is shown that Arabidopsis thaliana mutants deficient in plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase (gapcp1gapcp2) are ABA insensitive in growth, stomatal closure, and germination assays. The ABA levels of gapcp1gapcp2 were normal, suggesting that the ABA signal transduction pathway is impaired in the mutants. ABA modified gapcp1gapcp2 gene expression, but the mutant response to the hormone differed from that observed in wild-type plants. The gene expression of the transcription factor ABI4, involved in both sugar and ABA signalling, was altered in gapcp1gapcp2, suggesting that their ABA insensitivity is mediated, at least partially, through this transcriptional regulator. Serine supplementation was able partly to restore the ABA sensitivity of gapcp1gapcp2, indicating that amino acid homeostasis and/or serine metabolism may also be important determinants in the connections of ABA with primary metabolism. Overall, these studies provide new insights into the links between plant primary metabolism and ABA signalling, and demonstrate the importance of plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase in these interactions.

A critical role of plastidial glycolytic glyceraldehyde-3-phosphate dehydrogenase in the control of plant metabolism and development.

Glycolysis is a central metabolic pathway that provides energy and generates precursors for the synthesis of primary metabolites such as amino acids and fatty acids. In plants, glycolysis occurs in the cytosol and plastids, which complicates the understanding of this essential process. As a result, the contribution of each glycolytic pathway to the specific primary metabolite production and the degree of integration of both pathways is still unresolved. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described biochemically. But, up to now, little attention had been paid to GAPCps, probably because they have been considered as "minor isoforms" that catalyze a reversible reaction in plastids where it has been assumed that key glycolytic intermediates are in equilibrium with the cytosol. In the associated study, we have elucidated the crucial role of Arabidopsis GAPCps in the control of primary metabolism in plants. GAPCps deficiency affects amino acid and sugar metabolism and impairs plant development. Specifically, GAPCp deficiency affects the serine supply to roots, provoking a drastic phenotype of arrested root development. Also, we show that the phosphorylated serine biosynthesis pathway is critical to supply serine to non-photosynthetic organs such as roots. These studies provide new insights of the contribution of plastidial glycolysis to plant metabolism and evidence the complex interactions existing between metabolism and development.

Glyceraldehyde 3-phosphate dehydrogenase depletion induces cell cycle arrest and resistance to antimetabolites in human carcinoma cell lines.

Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a multifunctional protein that acts at the intersection of energy metabolism and stress response in tumor cells. To elucidate the role of GAPDH in chemotherapy-induced stress, we analyzed its activity, protein level, intracellular distribution, and intranuclear mobility in human carcinoma cells A549 and UO31 after treatment with cytarabine, doxorubicin, and mercaptopurine. After treatment with cytosine arabinoside (araC), enzymatically inactive GAPDH accumulated in the nucleus. Experiments on fluorescence recovery after photobleaching with green fluorescent protein-GAPDH fusion protein in the live cells treated with araC demonstrated reduced mobility of green fluorescent protein-GAPDH inside the nucleus, indicative of interactions with nuclear macromolecular components after genotoxic stress. Depletion of GAPDH with RNA interference stopped cell proliferation, and induced cell cycle arrest in G(1) phase via p53 stabilization, and accumulation of p53-inducible CDK inhibitor p21. Neither p21 accumulation nor cell cycle arrest was detected in GAPDH-depleted p53-null NCI-H358 cells. GAPDH-depleted A549 cells were 50-fold more resistant to treatment with cytarabine (1.68 +/- 0.182 microM versus 0.03 +/- 0.015 microM in control). Depletion of GAPDH did not significantly alter cellular sensitivity to doxorubicin (0.05 +/- 0.023 microM versus 0.035 +/- 0.0154 microM in control). Induction of cell cycle arrest in p53-proficient carcinoma cells via GAPDH abrogation suggests that GAPDH-depleting agents may have a cytostatic effect in cancer cells. Our results define GAPDH as an important determinant of cellular sensitivity to antimetabolite chemotherapy because of its regulatory functions.

Glyceraldehyde 3-phosphate dehydrogenase-S, a sperm-specific glycolytic enzyme, is required for sperm motility and male fertility.

Although glycolysis is highly conserved, it is remarkable that several unique isozymes in this central metabolic pathway are found in mammalian sperm. Glyceraldehyde 3-phosphate dehydrogenase-S (GAPDS) is the product of a mouse gene expressed only during spermatogenesis and, like its human ortholog (GAPD2), is the sole GAPDH isozyme in sperm. It is tightly bound to the fibrous sheath, a cytoskeletal structure that extends most of the length of the sperm flagellum. We disrupted Gapds expression by gene targeting to selectively block sperm glycolysis and assess its relative importance for in vivo sperm function. Gapds(-/-) males were infertile and had profound defects in sperm motility, exhibiting sluggish movement without forward progression. Although mitochondrial oxygen consumption was unchanged, sperm from Gapds(-/-) mice had ATP levels that were only 10.4% of those in sperm from WT mice. These results imply that most of the energy required for sperm motility is generated by glycolysis rather than oxidative phosphorylation. Furthermore, the critical role of glycolysis in sperm and its dependence on this sperm-specific enzyme suggest that GAPDS is a potential contraceptive target, and that mutations or environmental agents that disrupt its activity could lead to male infertility.

Adverse effects of dopamine potentiation by long-term treatment with selegiline.

A patient with triosephosphate isomerase (TPI) deficiency exhibited worsening of abnormal involuntary movements of the dystonic type and developed psychiatric symptoms while on selegiline. When selegiline was stopped after 9 years of treatment, abnormal involuntary movements improved to pretreatment level and psychiatric behaviour returned to normal. Monoamine oxidase-B platelet activity was low in this patient.

Reduction of glyceraldehyde-3-phosphate dehydrogenase activity in Alzheimer's disease and in Huntington's disease fibroblasts.

New functions have been identified for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) including its role in neurodegenerative disease and in apoptosis. GAPDH binds specifically to proteins implicated in the pathogenesis of a variety of neurodegenerative disorders including the beta-amyloid precursor protein and the huntingtin protein. However, the pathophysiological significance of such interactions is unknown. In accordance with published data, our initial results indicated there was no measurable difference in GAPDH glycolytic activity in crude whole-cell sonicates of Alzheimer's and Huntington's disease fibroblasts. However, subcellular-specific GAPDH-protein interactions resulting in diminution of GAPDH glycolytic activity may be disrupted or masked in whole-cell preparations. For that reason, we examined GAPDH glycolytic activity as well as GAPDH-protein distribution as a function of its subcellular localization in 12 separate cell strains. We now report evidence of an impairment of GAPDH glycolytic function in Alzheimer's and Huntington's disease subcellular fractions despite unchanged gene expression. In the postnuclear fraction, GAPDH was 27% less glycolytically active in Alzheimer's cells as compared with age-matched controls. In the nuclear fraction, deficits of 27% and 33% in GAPDH function were observed in Alzheimer's and Huntington's disease, respectively. This evidence supports a functional role for GAPDH in neurodegenerative diseases. The possibility is considered that GAPDH:neuronal protein interaction may affect its functional diversity including energy production and as well as its role in apoptosis.

A simple screening procedure for glucose phosphate isomerase, phosphofructokinase, aldolase and glyceraldehyde-3-phosphate dehydrogenase deficiencies.

A simple screening procedure for the detection of glucose-phosphate isomerase (GPI), phosphofructokinase (PFK), aldolase (AL) and glyceraldehyde-3-phosphate dehydrogenase (GAPD) deficiencies in blood, is described. These enzymes catalyze the second, third, fourth, and sixth reactions in the Embden-Meyerhof pathway. The procedure is based on the conversion of glucose-6-phosphate to 1,3-diphosphoglycerate (1,3-DPG) which is catalyzed by the sequential action of the GPI, PFK, AL and GAPD. The presence of the enzyme activities is visually estimated by the reduction of NAD+ (non-fluorescent) to NADH (fluorescent) which occurs when 1,3-DPG is formed. Absence of fluorescence indicates the deficiency of anyone of the four enzymes, which are specified by using separately the PFK, AL and GAPD respective substrates.

Clinical consequences of enzyme deficiencies in the erythrocyte.

The anucleate mature erythrocyte also lacks ribosomes and mitochondria and thus cannot synthesize enzymes or derive energy from the Krebs citric acid cycle. Nevertheless, the red blood cell is metabolically active and contains numerous residual enzymes and their products which are essential for its survival and normal functioning. Enzyme deficiencies in the Embden-Myerhoff glycolytic pathway can result in nonspherocytic hemolytic anemia (NSHA), and some are also associated with neuromuscular or neurologic disorders. Glucose-6-phosphate dehydrogenase deficiency in the hexose monophosphate shunt also results in hemolytic anemia, especially following exposure to various drugs. Defects in glutathione synthesis and pyrimidine 5'-nucleotidase deficiency also cause NSHA, as does increased adenosine deaminase activity. Gluthathione synthetase deficiency which is not limited to the red cell also presents as oxoprolinuria with neurologic signs. All red cell enzyme defects appear as single gene errors, in most cases recessive in inheritance, either autosomal of X-linked.

Erythrocyte enzyme deficiencies assessed with a miniature centrifugal analyzer.

Methods for assaying 16 erythrocyte enzymes have been adapted to the miniature centrifugal analyzer. Less than 15 micro L of whole blood is required for all 16 assays. Variation attributable to temporal effects, rotor effects, and random residual error is minor. Initial population studies of blood from adults and cord-blood samples suggest a CV of less than 12% for 12 of the 16 enzymes; thus it should be possible to identify the heterozygous deficient individual. Preliminary data suggest that three such individuals, with enzyme activity (adenylate kinase, pyruvate kinase, phosphoglycerate kinase) about half the expected, have been identified, as well as two individuals deficient in glucose-6-phosphate dehydrogenase.

[Enzyme deficiencies of blood cells in bone marrow insufficiency (author's transl]. / Enzymdefekte in Blutzellen bei Knochenmarkinsuffizienz.

Numerous enzyme defects-deficiency of pyruvate kinase, phosphofructo-kinase, glocosephosphate isomerase, adenylate kinase, 2,3-diphosphoglycerate mutase and glutathione reductase--in red blood cells have been described to be connected with dyserythropoietic or refractory anemias and panmyelopathies of different origin. These enzyme deficiencies also have been demonstrated in red cells of patients with acute leukemia. Most likely the enzyme deficiencies are acquired and are not important for the origin of anemia or bone marrow insufficiency. Partial derepression of fetal genes, qualitative and quantitative perturbations of genetic expression, and posttranslational variations of the enzyme protein by low molecular factors from plasma, erythrocytes or leukemic cells have been discussed as a reason of enzyme deficiency. The decrease of glutathione reductase deficiency is dependent of FAD deficiency.

[Enzyme deficiencies in glycolysis and nucleotide metabolism of red blood cells in nonspherocytic hemolytic anemia (author's transl)]. / Enzymdefekte in Glykolyse und Nukleotidstoffwechsel roter Blutzellen bei nichtsphärocytären hämolytischen Anämien

The detection of enzyme deficiencies in glycolytic and nucleotide metabolism of human red blood cells has enriched the pathophysiological knowledge on the origin of nonspherocytic hemolytic anemias (NSHA). So far for 11 of 13 glycolytic enzymes deficiencies have been described which are connected with alterations of biochemical enzymatic properties. The most frequent enzyme deficiencies are those of GPI and PK. By performance of special electrophoretic techniques genetic studies allow the demonstration of homozygote and double heterozygote defect carriers. Up to now only adenylate kinase and pyrimidine 5' nucleotidase deficiencies have been detected as genetically determined in altered nucleotide metabolism. The metabolic alterations of several enzymopathies have been characterized so well, that the pathophysiological relations between enzyme deficiency and NSHA probably have been found to be a sufficient explanation.

Study of a kindred with hereditary spherocytosis and glyceraldehyde-3-phosphate dehydrogenase deficiency.

A patient with hereditary spherocytosis (HS) was found to have glyceraldehyde-3-phosphate dehydrogenase (G3PD) deficiency by electrophoresis of the isolated red cell membranes on polyacrylamide gels with sodium dodecyl sulfate (PAGE SDS) as demonstrated by a diminished band 6 (G3PD) and confirmed by specific enzyme assay. Thirteen members of his family were studied: four were normal, two had HS alone, three had G3PD deficiency alone, and four had both HS and G3PD deficiency. G3PD deficient kindred members were probably heterozygous, since their red cell enzyme, while qualitatively normal, was present in half normal amounts. The G3PD deficiency alone was asymptomatic, and there was no evidence that the combination of HS with G3PD deficiency increased the clinical severity of the disease. However, G3PD deficiency, when combined with HS, was associated with an increase in protein band 4.5 on PAGE SDS. This band was also increased by incubation of normal red cells without glucose, and appeared to be a protein absorbed to the membrane as a consequence of metabolic stress. Hence, red cells with the combined abnormalities of both HS and G3PD deficiency showed signs of the exceptional metabolic stress to which they were exposed.

Catabolism of D-fructose and D-ribose by Pseudomonas doudoroffii. I. Physiological studies and mutant analysis.

Pseudomonas doudoroffii, a strict aerobe of marine origin, was able to utilize fructose and ribose but not glucose, gluconate, or other hexoses, pentoses, or sugar alcohols as sole sources of carbon and energy. Evidence was presented indicating that in this organism fructose was utilized via an inducible P-enolpyruvate: fructose phosphotransferase system (FPTS) which catalyzed the phosphorylation of fructose in the 1 position. The resulting fructose-1-P (F-1-P) was converted to fructose-1,6-P2 (FDP) by means of an inducible 1-P-fructokinase (1-PFK). The subsequent conversion of FDP to pyruvate involved enzymes of the Embden-Meyerhof pathway (EMP) which, with the exception of glyceraldehyde-3-P dehydrogenase (G3PDH), were constitutive. Two G3PDH activities were detected, one of which was inducible and NAD-dependent while the other was constitutive and NADP-dependent. Cell-free extracts of P. doudoroffii also contained enzymes of the methylglyoxal pathway (MGP) which converted dihydroxyacetone-P to pyruvate. The low specific activities of enzymes of this pathway as compared to the EMP suggested that the major route of FDP catabolism was via the latter pathway. 2. Ribose catabolism appeared to involve an inducible uptake system and an inducible ribokinase, the resulting ribose-5-P being converted to glyceraldehyde-3-P and fructose-6-P (F-6-P) by means of constitutive activities of the pentose-P pathway. The F-6-P formed as a result of these reactions was converted to FDP by means of a constitutive 6-P-fructokinase (6-PFK). Since no activity converting fructose or F-1-P to F-6-P could be detected in cell-free extracts of P. doudoroffii, the results suggested that fructose and ribose were catabolized via 1-PFK and 6-PFK, respectively, the two pathways converging at the level of FDP. Further evidence for this suggestion was obtained from a mutant which lacked an NAD-dependent G3PDH, accumulated FDP from both fructose and ribose, and was not able to grow on either of these compounds. 3. Ribose grown cells had increased amounts of the fructose uptake system and 1-PFK suggesting that a compound (or compounds) common to the catabolism of both fructose and ribose acted as the inducer(s) of these activities. Evidence was presented suggesting that the probable inducer(s) of 1-PFK and FPTS could be FDP, glyceraldehyde-3-P, or dihydroxyacetone-P. 4. A mutant unable to grow on fructose was characterized and found to lack FPTS while retaining 1-PFK and other enzyme activities of the EMP and MGP, indicating that a functional FPTS was essential for growth on fructose and suggesting that all or most of this sugar was catabolized via F-1-P.