UDP-glucose Pyrophosphorylase Activity Research Articles

The mechanistic study of using microparticle Al2O3 to promote the production of exopolysaccharides in submerged fermentation of Antrodia cinnamomea

In this study, a notable increase of 136.9% in the production of exopolysaccharides (EPS) was observed during the submerged fermentation of Antrodia cinnamomea when microparticle (4 g/L of Al2O3) was applied. By evaluating the activities of key enzymes involved in EPS synthesis in A. cinnamomea, it was found that the addition of Al2O3 enhanced the activities of phosphoglycerate mutase (PGM), UDP-glucose pyrophosphorylase (UGP), and GDP-mannose pyrophosphorylase (GMPPB). To further elucidate the mechanism through which Al2O3 enhances the production of EPS in A. cinnamomea, a transcriptomic analysis was conducted to compare the gene expression levels. The results showed that there was a significant up-regulation of genes associated with the synthesis and assembly of polysaccharide repeating units, as well as genes responsible for the regulation of ABC transporter complex enzymes. To verify the above hypothesis, the ABC transporter inhibitor MK-571 sodium salt was added to the fermentation broth of A. cinnamomea. The study demonstrated that when the ABC transporter was inhibited, the yield of EPS was significantly reduced, which further confirmed that the addition of Al2O3 could improve the activity of ABC transporter and promote the production of EPS in submerged fermentation of A. cinnamomea.

Abscisic Acid Regulates Carbohydrate Metabolism, Redox Homeostasis and Hormonal Regulation to Enhance Cold Tolerance in Spring Barley.

Abscisic acid (ABA) plays a vital role in the induction of low temperature tolerance in plants. To understand the molecular basis of this phenomenon, we performed a proteomic analysis on an ABA-deficit mutant barley (Az34) and its wild type (cv Steptoe) under control conditions (25/18 °C) and after exposure to 0 °C for 24 h. Most of the differentially abundant proteins were involved in the processes of photosynthesis and metabolisms of starch, sucrose, carbon, and glutathione. The chloroplasts in Az34 leaves were more severely damaged, and the decrease in Fv/Fm was larger in Az34 plants compared with WT under low temperature. Under low temperature, Az34 plants possessed significantly higher activities of ADP-glucose pyrophosphorylase, fructokinase, monodehydroascorbate reductase, and three invertases, but lower UDP-glucose pyrophosphorylase activity than WT. In addition, concentrations of proline and soluble protein were lower, while concentration of H2O2 was higher in Az34 plants compared to WT under low temperature. Collectively, the results indicated that ABA deficiency induced modifications in starch and sucrose biosynthesis and sucrolytic pathway and overaccumulation of reactive oxygen species were the main reason for depressed low temperature tolerance in barley, which provide novel insights to the response of barley to low temperature under future climate change.

Light calcium carbonate improves pullulan biosynthesis by Aureobasidium pullulans under high concentration of sugar.

The effects of light calcium carbonate (CaCO3) on pullulan biosynthesis by Aureobasidium pullulans NCPS2016 were investigated. Light CaCO3 enhanced pullulan production by 12.4% when added to the low concentration of fructose broth compared with K2HPO4. Pullulan production was further improved when increasing both the concentrations of light CaCO3 and fructose. Compared to K2HPO4, light CaCO3 improved the activities of UDP-glucose pyrophosphorylase, α-phosphoglucose mutase, UDP-glucosyltransferase, and glucosyltransferase relevant to pullulan biosynthesis, and the gene transcriptional levels of UDP-glucose pyrophosphorylase, α-phosphoglucose mutase, UDP-glucosyltransferase, and glucose kinase were enhanced. During 30-liter fermentation, 144.3g/L of purified pullulan was produced from 200g/L of fructose and 15g/L of light CaCO3 within 168h, with the yield and productivity of 0.72g/g and 0.86g/L/h respectively. This is the first report that light CaCO3 improves pullulan production significantly.

Nano-ZnO alleviates drought stress via modulating the plant water use and carbohydrate metabolism in maize

ABSTRACT The wide application of zinc oxide (ZnO) nanoparticles inevitably facilities their release into the terrestrial and agricultural ecosystems, severely affecting crop production. The effects of nano-ZnO (100 mg L−1) on stomatal morphology, gas exchange and key carbon metabolism enzyme activities were investigated in drought-stressed and well-watered maize. Drought stress limited the plant growth, caused stomatal closure, decreased the net photosynthetic rate, while increased the osmolyte concentrations. In drought-stressed maize, the application of nano-ZnO (100 mg L−1) alleviated photosynthetic pigment degradation and benefited the stomatal movement, maintained a higher net photosynthetic rate, and enhanced water use efficiency, promoting the drought tolerance in maize. In addition, the nano-ZnO increased the activities of UDP-glucose pyrophosphorylase, phosphoglucoisomerase and cytoplasmic invertase by 17.8%, 391.5% and 126%, respectively, which enhanced the starch and sucrose biosynthesis and glycolysis metabolism in leaves under drought stress. Manipulation of primary carbohydrate metabolism through nano-ZnO induced regulation of the key enzymes activity benefited the drought tolerance in maize. The nano-ZnO application (100 mg L−1) alleviates the negative effect of drought stress via improving photosynthetic carbon assimilation of maize.

Effect of 2-deoxy-D-glucose on gellan gum biosynthesis by Sphingomonas paucimobilis.

2-Deoxy-D-glucose (2-DG) is a non-metabolizable glucose analogue and competitive inhibitor of glycolysis. Effect of 2-DG on gellan gum biosynthesis by Sphingomonas paucimobilis ATCC31461 were studied in this research. The concentrationand the addition time of 2-DG significantly affected the biomass and gellan gum accumulation. The maximum gellan gum yield of 20.78g/L was obtained with the addition of 50µg/L of 2-DG at 24h. The mechanism of 2-DG addition favoring to gellan production was revealed by determining the activities of key enzymes. Results indicated that 2-DG addition increased the activities of glucosyltransferase and inhibited UDP-glucose pyrophosphorylase activity. The result indicated that 2-DG inhibited glycolysis and changed metabolic driving force to activate gellan gum biosynthesis metabolism pathways.

Sucrose synthesis in Unpollinated ovaries of pomegranate (Punica granatum L.), as well as, in reproductive and vegetative shoot apices

Sugar levels, the enzyme activity of UDP-Glucose Pyrophosphorylase (UGPase) and Sucrose Phosphate Synthase (SPS), key enzymes for sucrose synthesis, and the expression of their respective genes were examined in developing vegetative and reproductive shoot apices and in developing unpollinated ovaries of Pomegranate trees in order to detect differences possibly important for fruit production and plant vigor. The level of total sugars was higher in ovaries, followed by reproductive apices and vegetative apices, suggesting higher energy requirements in the reproductive organs. Moreover, the activities of SPS and UGPase were found to be elevated in the vegetative apices, indicating that sucrose synthesis is possibly differently regulated in comparison to the reproductive organs. Our results suggest that the sink power of each organ primarily regulates the levels of both transported (sucrose, mannitol) and non-transported (fructose, glucose) sugars. However, the endogenous production of sucrose may be a regulatory factor contributing to organ development.

UDP-glucose pyrophosphorylase: Isolation, purification and characterization from developing thermotolerant wheat (Triticum aestivum) grains

UDP-glucose pyrophosphorylase (UGPase, EC 2.7.7.9) activity was determined in four different thermotolerant varieties of wheat viz. WH-1021, PBW-373, Raj-3765 and DBW-16. The specific activity of UGPase was found to be highest at 21 days after anthesis (DAA) in the variety WH-1021 which has been developed by Haryana Agricultural University, Hisar (Haryana, India). Hence, crude extract prepared from immature grains (21 days after anthesis) of WH-1021 was used for purification of UGPase using standard protein purification techniques which exploit differences in protein properties viz. ammonium sulphate fractionation (based on solubility differences), DEAE-ion exchange chromatography (based on charge differences) and molecular sieving through Sephadex G-100 gel (based on molecular mass differences). Near homogeneous enzyme preparation with molecular mass of 82 kDa and subunit molecular weight of 39 kDa was obtained. The purified enzyme had thermostability upto 50 °C. Kinetic studies revealed that the enzyme followed Michaelis Menten kinetics with Km value of 0.9 mM and 1.66 mM for UDP and PPi, respectively. Physico-chemical and kinetic characterization suggested that the enzyme UGPase from WH-1021 is a homodimer which has adapted to high temperature stress and that lower availability of substrates and high Km values may be responsible for reduced starch synthesis/grain yield.

Improved mycelia and polysaccharide production of Grifola frondosa by controlling morphology with microparticle Talc

BackgroundMushroom showed pellet, clump and/or filamentous mycelial morphologies during submerged fermentation. Addition of microparticles including Talc (magnesium silicate), aluminum oxide and titanium oxide could control mycelial morphologies to improve mycelia growth and secondary metabolites production. Here, effect of microparticle Talc (45 μm) addition on the mycelial morphology, fermentation performance, monosaccharide compositions of polysaccharides and enzymes activities associated with polysaccharide synthesis in G. frondosa was well investigated to find a clue of the relationship between polysaccharide biosynthesis and morphological changes.ResultsAddition of Talc decreased the diameter of the pellets and increased the percentage of S-fraction mycelia. Talc gave the maximum mycelial biomass of 19.25 g/L and exo-polysaccharide of 3.12 g/L at 6.0 g/L of Talc, and mycelial polysaccharide of 0.24 g/g at 3.0 g/L of Talc. Talc altered the monosaccharide compositions/percentages in G. frondosa mycelial polysaccharide with highest mannose percentage of 62.76 % and lowest glucose percentage of 15.22 % followed with the corresponding changes of polysaccharide-synthesis associated enzymes including lowest UDP-glucose pyrophosphorylase (UGP) activity of 91.18 mU/mg and highest UDP-glucose dehydrogenase (UGDG) and GDP-mannose pyrophosphorylase (GMPPB) activities of 81.45 mU/mg and 93.15 mU/mg.ConclusionOur findings revealed that the presence of Talc significantly changed the polysaccharide production and sugar compositions/percentages in mycelial and exo-polysaccharides by affecting mycelial morphology and polysaccharide-biosynthesis related enzymes activities of G. frondosa.

Genome-Wide Association Mapping Reveals That Specific and Pleiotropic Regulatory Mechanisms Fine-Tune Central Metabolism and Growth in Arabidopsis.

Central metabolism is a coordinated network that is regulated at multiple levels by resource availability and by environmental and developmental cues. Its genetic architecture has been investigated by mapping metabolite quantitative trait loci (QTL). A more direct approach is to identify enzyme activity QTL, which distinguishes between cis-QTL in structural genes encoding enzymes and regulatory trans-QTL. Using genome-wide association studies, we mapped QTL for 24 enzyme activities, nine metabolites, three structural components, and biomass in Arabidopsis thaliana We detected strong cis-QTL for five enzyme activities. A cis-QTL for UDP-glucose pyrophosphorylase activity in the UGP1 promoter is maintained through balancing selection. Variation in acid invertase activity reflects multiple evolutionary events in the promoter and coding region of VAC-INVcis-QTL were also detected for ADP-glucose pyrophosphorylase, fumarase, and phosphoglucose isomerase activity. We detected many trans-QTL, including transcription factors, E3 ligases, protein targeting components, and protein kinases, and validated some by knockout analysis. trans-QTL are more frequent but tend to have smaller individual effects than cis-QTL. We detected many colocalized QTL, including a multitrait QTL on chromosome 4 that affects six enzyme activities, three metabolites, protein, and biomass. These traits are coordinately modified by different ACCELERATED CELL DEATH6 alleles, revealing a trade-off between metabolism and defense against biotic stress.

High-throughput proteome analysis reveals changes of primary metabolism and energy production under artificial aging treatment in Glycine max seeds

This study was conducted to obtain basic information on protein profile changes by artificial aging in soybean seeds. Seed proteins were extracted using the protamine sulfate precipitation method, which improves the detection of low-abundance proteins (LAPs) by depleting the major seed storage proteins . Isolated proteins were separated by high-resolution two-dimensional gel electrophoresis (2-DE), and differentially modulated protein spots were identified by MALDI-TOF/TOF. A total of 33 differential proteins were identified of which 31 and 2 showed decreased and increased abundances, respectively. Functional annotation of the identified proteins revealed that proteins were mainly associated with primary metabolism (55%) and response to stimulus (20.9%). Proteins with increased abundance were associated with nutrient reservoir activity (spots 5, 10), while the decreased abundance proteins were mainly involved in the primary metabolism such as carbohydrate metabolic process (spots 1–3, 11), protein folding (spots 6–9, 33), glucose metabolic process (spot 25) oxidoreductase activity (spots 19–24), UDP-glucose pyrophosphorylase activity (spots 12, 13). These results provide information about proteome changes, especially, LAPs during artificial seed aging treatment.

Sinorhizobium meliloti low molecular mass phosphotyrosine phosphatase SMc02309 modifies activity of the UDP-glucose pyrophosphorylase ExoN involved in succinoglycan biosynthesis.

In Gram-negative bacteria, tyrosine phosphorylation has been shown to play a role in the control of exopolysaccharide (EPS) production. This study demonstrated that the chromosomal ORF SMc02309 from Sinorhizobium meliloti 2011 encodes a protein with significant sequence similarity to low molecular mass protein-tyrosine phosphatases (LMW-PTPs), such as the Escherichia coli Wzb. Unlike other well-characterized EPS biosynthesis gene clusters, which contain neighbouring LMW-PTPs and kinase, the S. meliloti succinoglycan (EPS I) gene cluster located on megaplasmid pSymB does not encode a phosphatase. Biochemical assays revealed that the SMc02309 protein hydrolyses p-nitrophenyl phosphate (p-NPP) with kinetic parameters similar to other bacterial LMW-PTPs. Furthermore, we show evidence that SMc02309 is not the LMW-PTP of the bacterial tyrosine-kinase (BY-kinase) ExoP. Nevertheless, ExoN, a UDP-glucose pyrophosphorylase involved in the first stages of EPS I biosynthesis, is phosphorylated at tyrosine residues and constitutes an endogenous substrate of the SMc02309 protein. Additionally, we show that the UDP-glucose pyrophosphorylase activity is modulated by SMc02309-mediated tyrosine dephosphorylation. Moreover, a mutation in the SMc02309 gene decreases EPS I production and delays nodulation on Medicago sativa roots.

Effect of 1-methylcyclopropene on senescence and sugar metabolism in harvested broccoli florets

The effect of 1-methylcyclopropene (1-MCP) treatment on superficial color, sugar content and the activities of sugar metabolism enzymes, the expression of sucrose transporters and carbohydrate metabolizing enzymes in broccoli florets were investigated. Broccoli florets treated with 2.5μLL−1 of 1-methylcyclopropene (1-MCP) inhibited the increase of lightness (L*) value and retarded the decrease in hue angle (H) value and chlorophyll content. This treatment maintained higher levels of sugars comparing with control florets. In general, the activities of sucrose synthase-synthesis direction (SS-S) were enhanced in florets treated with 1-MCP, whereas the activities of sucrose synthase-cleavage direction (SS-C), glucokinase (GK) and UDP-glucose pyrophosphorylase (UGPase) were reduced. In addition, the expression of genes encoding sucrose transporters (BoSUC1 and BoSUC2) and carbohydrate metabolizing enzymes (BoINV1, BoHK1 and BoHK2) was induced upon 1-MCP treatment. These results indicated that 1-MCP can delay senescence of broccoli florets in the present study may be attributed to maintaining higher sugar content through regulation of sugar metabolism.

Genetic and biochemical characterization of genes involved in hyaluronic acid synthesis in Streptococcus zooepidemicus.

The biosynthetic pathway for hyaluronic acid (HA) has been proposed; however, a thorough genetic and functional analysis is required to further elucidate the roles of genes involved in HA production. Previously, we developed a markerless gene-deletion system for Streptococcus zooepidemicus and confirmed that hasA is essential for HA synthesis. Here, we constructed a comprehensive set of deletion mutants and investigated the roles of ten additional predicted genes in the HA synthetic pathway. Phenotypic assays revealed that all ten genes play a role in cell growth and/or HA synthesis. As expected, the deletion of hasA or hasB abolished HA production with little effect on growth, while the deletion of genes that are also required for peptidoglycan biosynthesis (hasE, glmM, and glmS) significantly reduced cell growth and HA production. Either of the glmU homologues (hasD and gcaD) was sufficient for optimal growth and the mucoid phenotype, while no double mutant could be isolated. Of the two UDP-glucose pyrophosphorylase (UGPase) paralogues, the operon-encoded hasC1 was responsible for 65% of the activity, while hasC2 was responsible for the remaining 35%. The deletion of hasC1 had no effect on cell growth and caused only a moderate decrease in the UDP-glucose level and HA production. The deletion of both hasC1 and hasC2 resulted in a severe growth defect and negligible UDP-glucose accumulation, HA production, and pyrophosphorylase activity. Of the two phosphoglucomutase paralogues, pgm1 and pgm2, the former is responsible for around 10% of activity, while the latter is responsible for 90%. The deletion of pgm1 showed no apparent effect on HA synthesis and growth, while the deletion of pgm2 resulted in the abolishment of HA synthesis and a significantly slower growth. These results should guide the metabolic engineering of S. zooepidemicus to improve HA productivity and quality.

Evidences for Chlorogenic Acid--A Major Endogenous Polyphenol Involved in Regulation of Ripening and Senescence of Apple Fruit.

To learn how the endogenous polyphenols may play a role in fruit ripening and senescence, apple pulp discs were used as a model to study the influences of chlorogenic acid (CHA, a major polyphenol in apple pulp) on fruit ripening and senescence. Apple (‘Golden Delicious’) pulp discs prepared from pre-climacteric fruit were treated with 50 mg L-1 CHA and incubated in flasks with 10 mM MES buffer (pH 6.0, 11% sorbitol). Compared to the control samples, treatment with CHA significantly reduced ethylene production and respiration rate, and enhanced levels of firmness and soluble solids content of the pulp discs during incubation at 25°C. These results suggested that CHA could retard senescence of the apple pulp discs. Proteomics analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and mass spectrometry (MALDI-TOF/TOF) revealed that the expressions of several key proteins correlated to fruit ripening and senescence were affected by the treatment with CHA. Further study showed that treating the pulp discs with CHA remarkably reduced levels of lipoxygenase, β-galactosidase, NADP-malic enzyme, and enzymatic activities of lipoxygenase and UDP-glucose pyrophosphorylase, all of which are known as promoters of fruit ripening and senescence. These results could provide new insights into the functions of endogenous phenolic compounds in fruit ripening and senescence.

On the Ancestral UDP-Glucose Pyrophosphorylase Activity of GalF from Escherichia coli.

In bacteria, UDP-glucose is a central intermediate in carbohydrate metabolism. The enzyme responsible for its synthesis is encoded by the galU gene and its deletion generates cells unable to ferment galactose. In some bacteria, there is a second gene, galF, encoding for a protein with high sequence identity to GalU. However, the role of GalF has been contradictory regarding its catalytic capability and not well understood. In this work we show that GalF derives from a catalytic (UDP-glucose pyrophosphorylase) ancestor, but its activity is very low compared to GalU. We demonstrated that GalF has some residual UDP-glucose pyrophosphorylase activity by in vitro and in vivo experiments in which the phenotype of a galU- strain was reverted by the over-expression of GalF and its mutant. To demonstrate its evolutionary path of “enzyme inactivation” we enhanced the catalysis by mutagenesis and showed the importance of the quaternary structure. This study provides important information to understand the structural and functional evolutionary origin of the protein GalF in enteric bacteria.

Enhanced gellan gum production by hydrogen peroxide (H2O2) induced oxidative stresses in Sphingomonas paucimobilis

In this study, the effect of H2O2-induced oxidative stress on gellan gum production and cell growth were investigated. Gellan gum production was improved and cell growth was inhibited by H2O2. A multiple H2O2 stresses with different concentrations were developed to optimize gellan gum production. A maximal gellan gum yield (22.52g/L), which was 35.58% higher than the control, was observed with 2, 2, 3, 4mmol/L H2O2 added at 6, 12, 18, 24h, respectively. Moreover, UDP-glucose pyrophosphorylase activity and glucosyltransferase activity were increased with H2O2 stresses. This new strategy of multiple H2O2-induced oxidative stresses would be further applied to gellan gum production in future study.

Over-expression of UDP-glucose pyrophosphorylase increases validamycin A but decreases validoxylamine A production in Streptomyces hygroscopicus var. jinggangensis 5008

During the fermentation of Streptomyces hygroscopicus TL01 to produce validamycin A (18 g/L), a considerable amount of an intermediate validoxylamine A (4.0 g/L) is accumulated. Chemical or enzymatic hydrolysis of validamycin A was not observed during the fermentation process. Over-expression of glucosyltransferase ValG in TL01 did not increase the efficiency of glycosylation. However, increased validamycin A and decreased validoxylamine A production were observed in both the cell-free extract and fermentation broth of TL01 supplemented with a high concentration of UDP-glucose. The enzymatic activity of UDP-glucose pyrophosphorylase (Ugp) in TL01, which catalyzes UDP-glucose formation, was found to be much lower than the activities of other enzymes involved in the biosynthesis of UDP-glucose and the glucosyltransferase ValG. An ugp gene was cloned from S . hygroscopicus 5008 and verified to code for Ugp. In TL01 with an extra copy of ugp, the transcription of ugp was increased for 1.5 times, and Ugp activity was increased by 100%. Moreover, 22 g/L validamycin A and 2.5 g/L validoxylamine A were produced, and the validamycin A/validoxylamine A ratio was increased from 3.15 in TL01 to 5.75. These data prove that validamycin A biosynthesis is limited by the supply of UDP-glucose, which can be relieved by Ugp over-expression.

Sucrose synthase dominates carbohydrate metabolism and relative growth rate in growing kiwifruit ( Actinidia deliciosa, cv Hayward)

Changes in fruit growth rate, carbohydrate content (glucose, fructose, sucrose and starch) and enzyme activity (sucrose synthase, UDPglucose pyrophosphorylase, fructokinase, glucokinase, sucrose phosphate synthase, ADPglucose pyrophosphorylase and invertases), in the external pericarp of kiwifruit, were measured throughout the growing season. Sucrose synthase showed the highest activity among the sucrose cleaving enzymes during large part of the growing season. The activity of invertases were much lower than that of sucrose synthase until ripening started. Sucrose synthase showed a tight although not linear relationship with the fruit RGR. Furthermore, sucrose synthase showed linear and significant correlations with the activities of both fructokinase and UDPglucose pyrophosphorylase indicating a strong co-regulation of the activities of these three enzymes involved in sucrose cleavage and sink strength, in kiwifruit. Sucrose synthase is suggested to be the dominating enzyme in the cleavage of imported carbon in kiwifruit, in tight coordination with fructokinase and UDPglucose pyrophosphorylase.

Strain improvement and metabolic flux modeling of wild-type and mutant Alcaligenes sp. NX-3 for synthesis of exopolysaccharide welan gum

Low-energy nitrogen ion beam implantation technique was used for the strain improvement of Alcaligenes sp. NX-3 for the production of exopolysaccharide welan gum. A high welan gum producing mutant, Alcaligenes sp. NX-3-1, was obtained through 20 keV N+ ion beam irradiation. Starting at a concentration of 50 g/L of glucose, mutant NX-3-1 produced 25.0 g/L of welan gum after 66 h of cultivation in a 7.5 L bioreactor, which was 34.4% higher than that produced by the wild-type strain. The results of metabolic flux analysis showed that the glucose-6-phosphate and acetyl coenzyme A nodes were the principle and flexible nodes, respectively. At the glucose-6-phosphate node, the fraction of carbon measured from glucose-6-phosphate to glucose-1-phosphate was enhanced after mutagenesis, which indicated that more flux was used to synthesize welan gum in the mutant. By analyzing the activities of related enzymes in the biosynthetic pathway of sugar nucleotides essential for welan gum production, we found that the specific activities of phosphoglucomutase, UDP-glucose pyrophosphorylase, UDP-glucose dehydrogenase, and dTDP-glucose pyrophosphorylase in the mutant strain were higher than those in the wild-type strain. These improvements in enzyme activities could be due to the affected of ion beam implantation.

Biosynthetic pathway of sugar nucleotides essential for welan gum production in Alcaligenes sp. CGMCC2428

Welan gum is a microbial polysaccharide produced by Alcaligenes sp. CGMCC2428 that has D-glucose, D-glucuronic acid, D-glucose, and L-rhamnose as the main structural unit. The biosynthetic pathway of sugar nucleotides essential for producing welan gum in this strain was established in the following ways: (1) the detection of the presence of several intermediates and key enzymes; (2) the analysis of the response upon addition of precursors to the culture medium; (3) the correlation of the activities between several key enzymes with the yields of welan gum. With addition of 200-microM glucose-6-phosphate and fructose-6-phosphate, the production of welan gum was improved by 18%. The activities of phosphoglucomutase, phosphomannose isomerase, UDP-glucose pyrophosphorylase, and dTDP-glucose pyrophosphorylase, correlated well with the yields of welan gum. According to these findings, the biosynthetic pathway was proposed to involve the metabolism of glucose via two discrete systems. The first involves conversion of glucose to glucose-6-phosphate, with further reactions producing glucose-1-phosphate and fructose-6-phosphate, which are metabolized to the nucleotide sugar precursors of welan gum. The second system involves metabolism of glucose to synthesize the basic structural skeleton of the cell via central metabolic pathways, including the Entner-Doudoroff pathway, the pentose phosphate pathway, and the tricarboxylic acid cycle.