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PubMed1982

Correlative histochemistry of some enzymes of carbohydrate metabolism in preneoplastic and neoplastic lesions in the rat liver.

The livers from a total of 51 Sprague-Dawley rats treated with different doses of N-nitrosomorpholine (80-120 mg/l in the drinking water) for up to 14 weeks together with the livers of 28 control animals were histochemically investigated at the cessation of carcinogenic insult and at varying periods thereafter for their glycogen content, basophilia and activities of various enzymes of carbohydrate metabolism: glycogen synthetase, glycogen phosphorylase, glucose-6-phosphatase, glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase. The enzymatic patterns of normal tissue, preneoplastic and neoplastic lesions were characterized and compared with reference to the morphologically defined stages of tumor development in the liver. The early appearing glycogen storing areas, localized in the peripheral and intermediate lobular regions, did not show significant changes in the histochemically demonstrable activities of the enzymes tested. After cessation of the carcinogen treatment the more pronounced glycogen storage foci which developed within the aforementioned regions of the liver acinus usually showed a reduction in the activities of phosphorylase and glucose-6-phosphatase while the activity of glucose-6-phosphate dehydrogenase, a key enzyme for the pentose phosphate pathway, was increased. The mixed cell foci, neoplastic nodules and tumors which emerged at later stages were characterized by a progressive shift away from glycogen metabolism towards glycolysis and the pentose phosphate pathway, as indicated by an increase in glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase activities. These changes in enzyme pattern are supportive of a developmental sequence leading from glycogen storage foci through mixed cell foci and neoplastic nodules to hepatocellular carcinomas.

Animals↗
PubMed1983

The effect of DDT on the polymorphism at the G6pd and Pgd loci in Drosophila melanogaster.

For the degradation of DDT and other chlorohydrocarbon insecticides energy in the form of NADPH is needed which for the greater part is supplied by the pentose phosphate shunt. Therefore the influence of DDT on the polymorphism at the G6pd and Pgd loci in Drosophila melanogaster was investigated by studying its effect on egg to adult survival and adult survival. The results show the existence of significant differences in fitness between the different genotypes of the two loci for both components. It is found that the effect of DDT supplementation differs significantly from the effect of sodium octanoate addition. DDT treatment also increases the activity of the pentose phosphate shunt as measured by the activity of G6PD and 6PGD. In larvae a 50% increase in activity is found and in adults a 100% increase. As there is little doubt that the activities of G6PD and 6PGD are somehow correlated with the fitness of flies, the data are discussed in relation to the in vitro and in vivo differences in activity between the different allozymes of both G6PD and 6PGD.

Animals↗
PubMed1994

Drosophila alcohol dehydrogenase polymorphism and carbon-13 fluxes: opportunities for epistasis and natural selection.

The influence of genetic variations in Drosophila alcohol dehydrogenase (ADH) on steady-state metabolic fluxes was studied by means of 13C NMR spectroscopy. Four pathways were found to be operative during 8 hr of ethanol degradation in third instar larvae of Drosophila. Seven strains differed by 18-25% in the ratio between two major pathway fluxes, i.e., into glutamate-glutamine-proline vs. lactate-alanine-trehalose. In general, Adh genotypes with higher ADH activity exhibit a twofold difference in relative carbon flux from malate into lactate and alanine vs. alpha,alpha-trehalose compared to low ADH activity genotypes. Trehalose was degraded by the pentose-phosphate shunt. The pentose-phosphate shunt and malic enzyme could supply NADPH necessary for lipid synthesis from ethanol. Lactate and/or proline synthesis may maintain the NADH/NAD+ balance during ethanol degradation. After 24 hr the flux into trehalose is increased, while the flux into lipids declines in AdhF larvae. In AdhS larvae the flux into lipids remains high. This co-ordinated nature of metabolism and the genotype-dependent differences in metabolic flux may form the basis for various epistatic interactions and ultimately for variations in organismal fitness.

Alanine↗
PubMed2002

Interaction of cytosolic and plastidic nitrogen metabolism in plants.

In angiosperms, the assimilation of ammonia resulting from nitrate reduction and from photorespiration depends on the operation of the plastidic GS/GOGAT cycle. The precursor for ammonia assimilation, 2-oxoglutarate, is synthesized in the mitochondria and in the cytosol. It is imported into the plastid by a 2-oxoglutarate/malate translocator (DiT1). In turn, the product of ammonia assimilation, glutamate, is exported from the plastids by a glutamate/malate translocator (DiT2). These transport processes link plastidic and cytosolic nitrogen metabolism and are essential for plant metabolism. DiT1 was purified to homogeneity from spinach chloroplast envelope membranes and identified as a protein with an apparent molecular mass of 45 kDa. Peptide sequences were obtained from the protein and the corresponding cDNA was cloned. The function of the DiT1 protein and its substrate specificity were confirmed by expression of the cDNA in yeast cells and functional reconstitution of the recombinant protein into liposomes. Recent advances in the molecular cloning of DiT2 and in the analysis of the in vivo function of DiT1 by antisense repression in transgenic tobacco plants will be discussed. In non-green tissues, the reducing equivalents required for glutamate formation by NADH-GOGAT are supplied by the oxidative pentose phosphate pathway. Glucose 6-phosphate, the immediate precursor of the oxidative pentose phosphate pathway is generated in the cytosol and imported into the plastids by the plastidic glucose 6-phosphate/phosphate translocator.

Amino Acid Oxidoreductases↗
PubMed1998

6-Phosphogluconate dehydrogenase is a 45-kDa antigen recognized by S4D5, a monoclonal antibody specific to vanadocytes in the vanadium-rich ascidian Ascidia sydneiensis samea.

We previously prepared a monoclonal antibody, S4D5, specific to vanadocytes, vanadium-containing blood cells, in the vanadium-rich ascidian Ascidia sydneiensis samea. Here, we demonstrate that a 45-kDa antigen recognized by S4D5 is 6-phosphogluconate dehydrogenase (6-PGDH), an enzyme of the pentose phosphate pathway, based on cDNA isolation of RNA samples from blood cells of the ascidian. Western blot analysis confirmed an abundance of 6-PGDH protein in the vanadocytes and localization of 6-PGDH in the soluble extract of the blood cells. Soluble protein exhibited a correspondingly high level of 6-PGDH enzymatic activity. Ascidians are known to selectively accumulate high levels of vanadium in vanadocytes, and the highest recorded concentration of accumulated vanadium is 350 mM, which is 10(7) times the concentration in sea water. Almost all vanadium ions are reduced to the +3 oxidation state via the +4 oxidation state in vanadocytes, indicating that reducing agents must participate in the accumulation. On the other hand, vanadium ions in the +5 oxidation state are reduced to the +4 oxidation state by the presence of NADPH in vitro. Together, these observations suggest that NADPH produced in the pentose phosphate pathway may conjugate the reduction of vanadium from the +5 oxidation state through the +4 oxidation state in vanadocytes of ascidians.

Amino Acid Sequence↗
PubMed2005

Engineering the substrate specificity of xylose isomerase.

Xylose isomerase (XI) catalyzes the isomerization and epimerization of hexoses, pentoses and tetroses. In order to clarify the reasons for the low reaction efficiency of a pentose sugar, L-arabinose, we determined the crystal structure of Streptomyces rubiginosus XI complexed with L-arabinose. The crystal structure revealed that, when compared with D-xylose and D-glucose, L-arabinose binds to the active site in a partially different position, in which the ligand has difficulties in binding the catalytic metal M2. Lys183 has been thought to stabilize the open substrate conformation by hydrogen bonding to oxygen O1. Our results with L-arabinose showed that the substrate stays in a linear form even without a hydrogen bond between Lys183 and oxygen O1. We engineered mutations to the active site of Actinoplanes missouriensis XI to improve the reaction efficiency with L-arabinose. The mutation F26W was intended to shift the position of oxygen O1 of L-arabinose closer to the catalytic metal M2. This effect of F26W was modeled by free energy perturbation simulations. In line with this, F26W increased 2-fold the catalytic efficiency of XI with L-arabinose; the increase was seen mainly in kcat. The mutation Q256D was outside the sphere of the catalytic residues and probably modified the electrostatic properties of the active site. It improved 3-fold the catalytic efficiency of XI with L-arabinose; this increase was seen in both Km and kcat. This study showed that it is possible to engineer the substrate specificity of XI.

Aldose-Ketose Isomerases↗
PubMed2002

Mutation of rpiA in Enterobacter cloacae decreases seed and root colonization and biocontrol of damping-off caused by Pythium ultimum on cucumber.

Strains of Enterobacter cloacae show promise as biocontrol agents for Pythium ultimum-induced damping-off on cucumber and other crops. E. cloacae A145 is a mini-Tn5 Km transposon mutant of strain 501R3 that was significantly reduced in suppression of damping-off on cucumber caused by P. ultimum. Strain A145 was deficient in colonization of cucumber, sunflower, and wheat seeds and significantly reduced in colonization of corn and cowpea seeds relative to strain 501R3. Populations of strain A145 were also significantly lower than those of strain 501R3 at all sampling times in cucumber, wheat, and sunflower rhizosphere. Populations of strain A145 were not detectable in any rhizosphere after 42 days, while populations of strain 501R3 remained at substantial levels throughout all experiments. Molecular characterization of strain A145 indicated mini-Tn5 Km was inserted in a region of the E. cloacae genome with a high degree of DNA and amino acid sequence similarity to rpiA, which encodes ribose-5-phosphate isomerase. In Escherichia coli, RpiA catalyzes the interconversion of ribose-5-phosphate and ribulose-5-phosphate and is a key enzyme in the pentose phosphate pathway. Ribose-5-phosphate isomerase activity in cell lysates from strain A145 was approximately 3.5% of that from strain 501R3. In addition, strain A145 was a ribose auxotroph, as expected for an rpiA mutant. Introduction of a 1.0-kb DNA fragment containing only the rpiA homologue into strain A145 restored ribose phosphate isomerase activity, prototrophy, seedling colonization, and disease suppression to levels similar to those associated with strain 501R3. Experiments reported here indicate a key role for rpiA and possibly the pentose phosphate pathway in suppression of damping-off and colonization of subterranean portions of plants by E. cloacae.

Cucumis sativus↗
PubMed1994

Glucose-6-phosphate dehydrogenase: a "housekeeping" enzyme subject to tissue-specific regulation by hormones, nutrients, and oxidant stress.

The enzyme, glucose-6-phosphate dehydrogenase (G6PDH, EC1.1.1.49), has long been considered and studied as the archetypical X-linked "housekeeping" enzyme that is present in all cells, where it plays the key role in regulating carbon flow through the pentose phosphate pathway. Specifically, the enzyme catalyzes the first reaction in the pathway leading to the production of pentose phosphates and reducing power in the form of NADPH for reductive biosynthesis and maintenance of the redox state of the cell. It was in this latter function that the crucial importance of the enzyme was first appreciated with the description of the human deficiency syndrome. While the gene can be considered to be a constitutively expressed "housekeeping" gene in many tissues, there are several other tissues (liver, adipose, lung, and proliferating cells) wherein modulation of cellular G6PDH activity represents an important component of the integrated response to external stimuli (hormones, growth factors, nutrients, and oxidant stress). In this regard, adaptive regulation of G6PDH has been found to be exerted at transcriptional and posttranscriptional levels. However, the regulation observed is tissue-specific, which elicits the central question of this review, "How can the G6PDH gene be constitutively expressed in some tissues while displaying adaptive regulation in others when there exists a single transcription unit for the gene?" Future studies utilizing cloned genomic fragments of the human and other mammalian G6PDH genes should provide answers to this question.

Amino Acid Sequence↗
PubMed1987

Dapsone-associated Heinz body hemolytic anemia in a Cambodian woman with hemoglobin E trait.

A Cambodian woman with hemoglobin E trait (AE) and leprosy developed a Heinz body hemolytic anemia while taking a dose of dapsone (50 mg/day) not usually associated with clinical hemolysis. Her red blood cells (RBCs) had increased incubated Heinz body formation, decreased reduced glutathione (GSH), and decreased GSH stability. The pentose phosphate shunt activity of the dapsone-exposed AE RBCs was increased compared to normal RBCs. Although the AE RBCs from an individual not taking dapsone had increased incubated Heinz body formation, the GSH content and GSH stability were normal. The pentose phosphate shunt activity of the non-dapsone-exposed AE RBCs was decreased compared to normal RBCs. Thus, AE RBCs appear to have an increased sensitivity to oxidant stress both in vitro and in vivo, since dapsone does not cause hemolytic anemia at this dose in hematologically normal individuals. Given the influx of Southeast Asians into the United States, oxidant medications should be used with caution, especially if an infection is present, in individuals of ethnic backgrounds that have an increased prevalence of hemoglobin E.

2,3-Diphosphoglycerate↗
PubMed1996

Changes in glucose transporter 2 and carbohydrate-metabolizing enzymes in the liver during cold preservation and warm ischemia.

In order to examine glucose metabolism in liver grafts during cold preservation (24 and 48 hr), warm ischemia (60 and 120 min), a combination of the two and reperfusion, the amount of protein and mRNA of glucose transporter 2 and the activities of enzymes in glycolysis (glucokinase, phosphofructokinase, pyruvatekinase), gluconeogenesis (glucose 6-phosphatase, fructose 1,6-bisphosphatase), and the pentose phosphate pathway (glucose 6-phosphate dehydrogenase) were measured. It appeared that glucose transport, the pentose phosphate pathway, and gluconeogenesis were maintained during cold preservation and warm ischemia. The activity of glucokinase significantly decreased from the control value of 1.33 +/- 0.23 IU/g protein to 0.70 +/- 0.17 (24 hr, P<0.05) and 0.57 +/- 0.12 (48 hr, P<0.01) only during cold preservation. However, the activity of phosphofructokinase significantly decreased from the control value of 4.37 +/- 0.06 IU/g protein to 2.67 +/- 0.15 (60 min, P<0.0001) and 1.53 +/- 0.06 (120 min, P<0.0001) only during warm ischemia. This indicates that glycolysis deteriorates during both cold preservation and warm ischemia and demonstrates further that the balance between glycolysis and gluconeogenesis shifts to gluconeogenesis. Even when cold preservation was combined with warm ischemia, the activity of glucokinase decreased only during cold preservation and the activity of phosphofructokinase decreased only during warm ischemia. Furthermore, these changes were time-dependent. It is suggested that they can be used as a clock to measure the durations of cold preservation and warm ischemia separately and that the magnitude of an ischemic injury to a liver and a liver graft's viability can be indirectly estimated before transplantation.

Animals↗
PubMed2005

[1,2-13C2]-D-glucose profiles of the serum, liver, pancreas, and DMBA-induced pancreatic tumors of rats.

OBJECTIVES: In vitro stable isotope glucose tracer studies indicate that undifferentiated cells of the pancreas use glucose primarily through the nonoxidative reactions of the pentose cycle for nucleic acid ribose synthesis, whereas normal or less transformed cells primarily use the oxidative branch of the cycle. METHODS: The pancreatic heads of 4 groups (5/group) of male rats were implanted with time-release pellets designed to deliver placebo or 7,12-dimethylbenzanthracene (DMBA) at 11, 33, or 56 mg/d. Four weeks after pancreatic exposure to DMBA, [1,2-C2]-D-glucose tracer (1 g/kg) was injected intraperitoneally followed by sera collection at 1 and 2 hours and harvest of tumors, adjacent pancreatic tissue, and sera at 3 hours. RESULTS: Tumors (2-9 mm) were found across DMBA groups, with the largest in the high-dose group (> or =5 mm). Selective monitoring by gas chromatography-mass spectrometry of the doubly-labeled [1,2-C2]-D-ribose of RNA, which requires nonoxidative synthesis in the pentose cycle, showed a 2.8-, 2.9-, and 5.7-fold increase in pancreatic tumors. Liver and adjacent pancreas preferentially produced [1-C1]-D-ribose through the oxidative reactions of the cycle. Tumor-bearing animals also cleared and recycled tracer glucose at a faster rate. CONCLUSIONS: Simultaneous selective positional ion monitoring of C-labeled metabolites and their mass isotopomers in tissues and blood opens new avenues for the early detection and response to therapy testing of pancreatic cancer using GC-MS and/or magnetic resonance imaging-based methods. This study emphasizes the benefits of stable isotope-based dynamic metabolic profiling, when applied in vivo, and the several advantages it offers to positron emission tomography.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Genes for D-arabinitol and ribitol catabolism from Klebsiella pneumoniae.

The enzymes for catabolism of the pentitols D-arabinitol (Dal) and ribitol (Rbt) and the corresponding genes from Klebsiella pneumoniae (dal and rbt) and Escherichia coli (atl and rtl) have been used intensively in experimental evolutionary studies. Four dal and four rbt genes from the chromosome of K. pneumoniae 1033-5P14 were cloned and sequenced. These genes are clustered in two adjacent but divergently transcribed operons and separated by two convergently transcribed repressor genes, dalR and rbtR. Each operon encodes an NAD-dependent pentose dehydrogenase (dalD and rbtD), and ATP-dependent pentulose kinase (dalK and rbtK) and a pentose-specific ion symporter (dalT and rbtT). Although the biochemical reactions which they catalyse are highly similar, the enzymes showed interesting deviations. Thus, DalR (313 aa) and RbtR (270 aa) belong to different repressor families, and DalD (455 aa) and RbtD (248 aa), which are active as a monomer or as tetramers, respectively, belong to different dehydrogenase families. Of the two kinases (19.3% identity), DalK (487 aa) belongs to the subfamily of short D-xylulokinases and RbtK (D-ribulokinase; 535 aa) to the subfamily of long kinases. The repressor, dehydrogenase and kinase genes did not show extensive similarity beyond local motifs. This contrasts with the ion symporters (86.6% identity) and their genes (82.7% identity). Due to their unusually high similarity, parts of dalT and rbtT have previously been claimed erroneously to correspond to 'inverted repeats' and possible remnants of a 'metabolic transposon' comprising the dal and rbt genes. Other characteristic structures, e.g. a secondary att lambda site and chi-like sites, as well as the conservation of this gene group in E. coli C are also discussed.

Amino Acid Sequence↗
PubMed1995

Glucose metabolism in 'Sphingomonas elodea': pathway engineering via construction of a glucose-6-phosphate dehydrogenase insertion mutant.

'Sphingomonas (formerly Pseudomonas) elodea' produces the industrially important polysaccharide gellan when grown in media containing glucose. Glucose catabolic enzymes and enzymes of central carbon metabolism were assayed in crude extracts of glucose-grown cultures of this bacterium. Based on these analyses it was concluded that glucose is converted to either gluconate or glucose 6-phosphate and that both of these products are converted to 6-phosphogluconate, a precursor for the Entner-Doudoroff (ED) and pentose phosphate pathways. Phosphoglucoisomerase (Pgi) activity was detected, but the lack of phosphofructokinase activity indicated that the Embden-Meyerhof glycolytic pathway is non-functional for glucose degradation. Thus, this bacterium utilizes glucose mainly via the ED and pentose phosphate pathways. Enzyme analyses suggested the involvement of glucose-6-phosphate dehydrogenase (Zwf) in glucose utilization and CO2 production. The zwf gene was cloned from 'S. elodea' and partially sequenced, and a null zwf mutant was constructed. This mutant exhibited no Zwf activity in in vitro assays, grew normally on glucose minimal medium and accumulated biomass (cells plus gellan) and produced CO2 at the same rates as the parental strain. Potential explanations for this finding are provided. Clones carrying the pgi gene were isolated fortuitously.

Amino Acid Sequence↗
PubMed2005

CreA influences the metabolic fluxes of Aspergillus nidulans during growth on glucose and xylose.

The physiological phenotype of Aspergillus nidulans was investigated for different genetic and environmental conditions of glucose repression through the quantification of in vivo fluxes in the central carbon metabolism using (13)C-metabolic-flux analysis. The particular focus was the role of the carbon repressor CreA, which is the major regulatory protein mediating carbon repression in many fungal species, in the primary metabolism of A. nidulans. Batch cultivations were performed with a reference strain and a deletion mutant strain (creADelta4) using [1-(13)C]glucose as carbon source. The mutant strain was also grown on a mixture of [1-(13)C]glucose and unlabelled xylose. Fractional enrichment data were measured by gas chromatography-mass spectrometry. A model describing the central metabolism of A. nidulans was used in combination with fractional enrichment data, and measurements of extracellular rates and biomass composition for the estimation of the in vivo metabolic fluxes. The creA-mutant strain showed a lower maximum specific growth rate than the reference strain when grown on glucose (0.11 and 0.25 h(-1), respectively), whereas the specific growth rate of the mutant strain grown on the glucose/xylose mixture was identical to that on glucose (0.11 h(-1)). Different patterns and increased levels of extracellular polyols were observed both upon deletion of the creA gene and upon addition of xylose to the growth medium of the mutant strain. Concerning metabolic fluxes, the major change observed in the flux distribution of A. nidulans upon deletion of the creA gene was a 20 % decrease in the flux through the oxidative part of the pentose-phosphate pathway. Addition of xylose to the growth medium of the mutant resulted in an increase of about 40 % in the activity of the oxidative part of the pentose-phosphate pathway, as well as decreases in the fluxes through the Embden-Meyerhof-Parnas pathway and the tricarboxylic acid cycle (in the range of 20-30 %). The derepression of key pathways leads to alterations in the demands for cofactors, thereby imposing changes in the central metabolism due to the coupling of the many different reactions via the redox and energy metabolism of the cells.

Aspergillus nidulans↗
PubMed2000

Coordinate changes in carbon partitioning and plastidial metabolism during the development of oilseed rape embryos.

Measurements of metabolic fluxes in whole embryos and isolated plastids have revealed major changes in the pathways of carbon utilization during cotyledon filling by oilseed rape (Brassica napus L.) embryos. In the early cotyledon stage (stage A), embryos used sucrose (Suc) predominantly for starch synthesis. Plastids isolated from these embryos imported glucose-6-phosphate (Glc-6-P) and partitioned it to starch and fatty acids synthesis and to the oxidative pentose phosphate pathway in the ratio of 2:1:1 on a hexose basis. Of the substrates tested, Glc-6-P gave the highest rates of fatty acid synthesis by the plastids and pyruvate was used weakly. By the mid- to late-cotyledon stage (stage C), oil accumulation by the embryos was rapid, as was their utilization of Suc for oil synthesis in vitro. Plastids from C-stage embryos differed markedly from those of stage-A embryos: (a) pyruvate uptake and utilization for fatty acid synthesis increased by respectively 18- and 25-fold; (b) Glc-6-P partitioning was predominantly to the oxidative pentose phosphate pathway (respective ratios of 1:1:3); and (c) the rate of plastidial fatty acid synthesis more than doubled. This increased rate of fatty synthesis was dependent upon the increase in pyruvate uptake and was mediated through the induction of a saturable transporter activity.

Brassica↗
PubMed1966

Ontogenetic changes in respiratory pathways in cortland apple skin during storage.

Ontogenic changes in respiratory pathways of skins of detached apple fruits were measured during a 4 month period. Results showed that an increase in pentose pathway occurred with increasing senescence in this tissue. Variation in temperature at any given age did not result in an alteration of the C(6)/C(1) ratio. CO(2) evolution from the pentose pathway in senescent fruit was directly related to O(2) uptake. Glucose uptake increased with increasing senescence indicating a change in cell permeability.

Journal Article↗
PubMed1966

Metabolism of red beet slices I. Effects of washing.

The changes in relative participation of pathways of glucose catabolism in red beet slices during washing have been examined using specifically (14)C labeled glucoses. Washing of these slices brings about an increase in participation of the pentose phosphate pathway. The composition of the washing medium influences slightly the extent of change in pathway participation. The activity level of certain enzymes participating in the initial stages of glucose catabolism has been measured in fresh and washed beet slices. Fresh slices which barely metabolized gluconate were found to have very little 6-phosphogluconate dehydrogenase activity. Washing brings about a dramatic increase in 6-phosphogluconate dehydrogenase activity and this increase was accompanied by a marked increase in the ability of the slices to metabolize gluconate. In red beet slices the TPNH generated via pentose phosphate pathway appears to be utilized for biosynthetic reductions rather than as respiratory substrate.

Journal Article↗
PubMed1966

Metabolism of Red Beet Slices II. Effects of Aging.

The rate of respiration of red beet slices increased 3- to 4-fold when the slices were aged in a moist atmosphere for 18 to 24 hours. The respiration of fresh slices was severely inhibited by 8 x 10(-5)m HCN but as slices aged the sensitivity of respiration to HCN fell rapidly. The presence of HCN stimulated the respiration of slices after 8 to 12 hours of aging.The relative participation of the pentose phosphate pathway in the glucose catabolism increased very little, if any, during aging of slices prepared from beets in the growing phase although the total metabolic rate seems to be greatly increased. However, data obtained from slices prepared from dormant beets indicated a possible increase in pentose phosphate pathway participation in glucose catabolism upon aging. The activity of 6-phosphogluconate dehydrogenase increased very markedly during aging and a corresponding marked increase in the ability of the tissue to metabolize gluconate was observed. It is concluded that to associate the aging process of storage tissue slices with a specific increase in a particular pathway is not justifiable.

Journal Article↗