scholarly journals Confirmation and Elimination of Xylose Metabolism Bottlenecks in Glucose Phosphoenolpyruvate-Dependent Phosphotransferase System-Deficient Clostridium acetobutylicum for Simultaneous Utilization of Glucose, Xylose, and Arabinose

2011 ◽  
Vol 77 (22) ◽  
pp. 7886-7895 ◽  
Author(s):  
Han Xiao ◽  
Yang Gu ◽  
Yuanyuan Ning ◽  
Yunliu Yang ◽  
Wilfrid J. Mitchell ◽  
...  
Keyword(s):  
Clostridium Acetobutylicum ◽  
Xylose Isomerase ◽  
Cost Effective ◽  
Pentose Phosphate ◽  
Xylose Metabolism ◽  
Phosphotransferase System ◽  
Gene Encoding ◽  
Content Type ◽  
Sugar Mixtures ◽  
Residual Glucose

ABSTRACTEfficient cofermentation ofd-glucose,d-xylose, andl-arabinose, three major sugars present in lignocellulose, is a fundamental requirement for cost-effective utilization of lignocellulosic biomass. The Gram-positive anaerobic bacteriumClostridium acetobutylicum, known for its excellent capability of producing ABE (acetone, butanol, and ethanol) solvent, is limited in using lignocellulose because of inefficient pentose consumption when fermenting sugar mixtures. To overcome this substrate utilization defect, a predictedglcGgene, encoding enzyme II of thed-glucose phosphoenolpyruvate-dependent phosphotransferase system (PTS), was first disrupted in the ABE-producing model strainClostridium acetobutylicumATCC 824, resulting in greatly improvedd-xylose andl-arabinose consumption in the presence ofd-glucose. Interestingly, despite the loss of GlcG, the resulting mutant strain 824glcG fermentedd-glucose as efficiently as did the parent strain. This could be attributed to residual glucose PTS activity, although an increased activity of glucose kinase suggested that non-PTS glucose uptake might also be elevated as a result ofglcGdisruption. Furthermore, the inherent rate-limiting steps of thed-xylose metabolic pathway were observed prior to the pentose phosphate pathway (PPP) in strain ATCC 824 and then overcome by co-overexpression of thed-xylose proton-symporter (cac1345),d-xylose isomerase (cac2610), and xylulokinase (cac2612). As a result, an engineered strain (824glcG-TBA), obtained by integratingglcGdisruption and genetic overexpression of the xylose pathway, was able to efficiently coferment mixtures ofd-glucose,d-xylose, andl-arabinose, reaching a 24% higher ABE solvent titer (16.06 g/liter) and a 5% higher yield (0.28 g/g) compared to those of the wild-type strain. This strain will be a promising platform host toward commercial exploitation of lignocellulose to produce solvents and biofuels.

scholarly journals Phosphotransferase System-Mediated Glucose Uptake Is Repressed in Phosphoglucoisomerase-Deficient Corynebacterium glutamicum Strains

2013 ◽  
Vol 79 (8) ◽  
pp. 2588-2595 ◽  
Author(s):  
Steffen N. Lindner ◽  
Dimitar P. Petrov ◽  
Christian T. Hagmann ◽  
Alexander Henrich ◽  
Reinhard Krämer ◽  
...  
Keyword(s):  
Amino Acid ◽  
Glucose Uptake ◽  
Corynebacterium Glutamicum ◽  
Pentose Phosphate ◽  
Phosphotransferase System ◽  
Negative Effects ◽  
Gene Encoding ◽  
Lysine Production ◽  
Content Type ◽  
Model Strain

ABSTRACTCorynebacterium glutamicumis particularly known for its industrial application in the production of amino acids. Amino acid overproduction comes along with a high NADPH demand, which is covered mainly by the oxidative part of the pentose phosphate pathway (PPP). In previous studies, the complete redirection of the carbon flux toward the PPP by chromosomal inactivation of thepgigene, encoding the phosphoglucoisomerase, has been applied for the improvement ofC. glutamicumamino acid production strains, but this was accompanied by severe negative effects on the growth characteristics. To investigate these effects in a genetically defined background, we deleted thepgigene in the type strainC. glutamicumATCC 13032. The resulting strain,C. glutamicumΔpgi, lacked detectable phosphoglucoisomerase activity and grew poorly with glucose as the sole substrate. Apart from the already reported inhibition of the PPP by NADPH accumulation, we detected a drastic reduction of the phosphotransferase system (PTS)-mediated glucose uptake inC. glutamicumΔpgi. Furthermore, Northern blot analyses revealed that expression ofptsG, which encodes the glucose-specific EII permease of the PTS, was abolished in this mutant. Applying our findings, we optimizedl-lysine production in the model strainC. glutamicumDM1729 by deletion ofpgiand overexpression of plasmid-encodedptsG.l-Lysine yields and productivity withC. glutamicumΔpgi(pBB1-ptsG) were significantly higher than those withC. glutamicumΔpgi(pBB1). These results show thatptsGoverexpression is required to overcome the repressed activity of PTS-mediated glucose uptake inpgi-deficientC. glutamicumstrains, thus enabling efficient as well as fastl-lysine production.

scholarly journals Novel Listerial Glycerol Dehydrogenase- and Phosphoenolpyruvate-Dependent Dihydroxyacetone Kinase System Connected to the Pentose Phosphate Pathway

2012 ◽  
Vol 194 (18) ◽  
pp. 4972-4982 ◽  
Author(s):  
Céline Monniot ◽  
Arthur Constant Zébré ◽  
Francine Moussan Désirée Aké ◽  
Josef Deutscher ◽  
Eliane Milohanic
Keyword(s):  
Pentose Phosphate Pathway ◽  
Triosephosphate Isomerase ◽  
Pentose Phosphate ◽  
Glycerol Dehydrogenase ◽  
Phosphoryl Group ◽  
Phosphotransferase System ◽  
Gene Encoding ◽  
Content Type ◽  
New Type ◽  
Enzyme I

ABSTRACTSeveral bacteria use glycerol dehydrogenase to transform glycerol into dihydroxyacetone (Dha). Dha is subsequently converted into Dha phosphate (Dha-P) by an ATP- or phosphoenolpyruvate (PEP)-dependent Dha kinase.Listeria innocuapossesses two potential PEP-dependent Dha kinases. One is encoded by 3 of the 11 genes forming the glycerol (gol) operon. This operon also containsgolD(lin0362), which codes for a new type of Dha-forming NAD+-dependent glycerol dehydrogenase. The subsequent metabolism of Dha requires its phosphorylation via the PEP:sugar phosphotransferase system components enzyme I, HPr, and EIIADha-2 (Lin0369). P∼EIIADha-2 transfers its phosphoryl group to DhaL-2, which phosphorylates Dha bound to DhaK-2. The resulting Dha-P is probably metabolized mainly via the pentose phosphate pathway, because two genes of thegoloperon encode proteins resembling transketolases and transaldolases. In addition, purified Lin0363 and Lin0364 exhibit ribose-5-P isomerase (RipB) and triosephosphate isomerase activities, respectively. The latter enzyme converts part of the Dha-P into glyceraldehyde-3-P, which, together with Dha-P, is metabolized via gluconeogenesis to form fructose-6-P. Together with another glyceraldehyde-3-P molecule, the transketolase transforms fructose-6-P into intermediates of the pentose phosphate pathway. Thegoloperon is preceded bygolR, transcribed in the opposite orientation and encoding a DeoR-type repressor. Its inactivation causes the constitutive but glucose-repressible expression of the entiregoloperon, including the last gene, encoding a pediocin immunity-like (PedB-like) protein. Its elevated level of synthesis in thegolRmutant causes slightly increased immunity against pediocin PA-1 compared to the wild-type strain or apedB-like deletion mutant.

scholarly journals Hierarchy in Pentose Sugar Metabolism in Clostridium acetobutylicum

2014 ◽  
Vol 81 (4) ◽  
pp. 1452-1462 ◽  
Author(s):  
Ludmilla Aristilde ◽  
Ian A. Lewis ◽  
Junyoung O. Park ◽  
Joshua D. Rabinowitz
Keyword(s):  
Clostridium Acetobutylicum ◽  
Sugar Metabolism ◽  
Pentose Phosphate ◽  
Acetyl Phosphate ◽  
Content Type ◽  
Acetate Excretion ◽  
Terrestrial Carbon Cycle ◽  
Pentose Sugar ◽  
Phosphoketolase Pathway ◽  
Pentose Sugars

ABSTRACTBacterial metabolism of polysaccharides from plant detritus into acids and solvents is an essential component of the terrestrial carbon cycle. Understanding the underlying metabolic pathways can also contribute to improved production of biofuels. Using a metabolomics approach involving liquid chromatography-mass spectrometry, we investigated the metabolism of mixtures of the cellulosic hexose sugar (glucose) and hemicellulosic pentose sugars (xylose and arabinose) in the anaerobic soil bacteriumClostridium acetobutylicum. Simultaneous feeding of stable isotope-labeled glucose and unlabeled xylose or arabinose revealed that, as expected, glucose was preferentially used as the carbon source. Assimilated pentose sugars accumulated in pentose phosphate pathway (PPP) intermediates with minimal flux into glycolysis. Simultaneous feeding of xylose and arabinose revealed an unexpected hierarchy among the pentose sugars, with arabinose utilized preferentially over xylose. The phosphoketolase pathway (PKP) provides an alternative route of pentose catabolism inC. acetobutylicumthat directly converts xylulose-5-phosphate into acetyl-phosphate and glyceraldehyde-3-phosphate, bypassing most of the PPP. When feeding the mixture of pentose sugars, the labeling patterns of lower glycolytic intermediates indicated more flux through the PKP than through the PPP and upper glycolysis, and this was confirmed by quantitative flux modeling. Consistent with direct acetyl-phosphate production from the PKP, growth on the pentose mixture resulted in enhanced acetate excretion. Taken collectively, these findings reveal two hierarchies in clostridial pentose metabolism: xylose is subordinate to arabinose, and the PPP is used less than the PKP.

scholarly journals Regulatory Tasks of the Phosphoenolpyruvate-Phosphotransferase System of Pseudomonas putida in Central Carbon Metabolism

mBio ◽  
2012 ◽  
Vol 3 (2) ◽  
Author(s):  
Max Chavarría ◽  
Roelco J. Kleijn ◽  
Uwe Sauer ◽  
Katharina Pflüger-Grau ◽  
Víctor de Lorenzo
Keyword(s):  
Pseudomonas Putida ◽  
Metabolic Networks ◽  
Tca Cycle ◽  
High Energy ◽  
Pentose Phosphate ◽  
Cell Physiology ◽  
Phosphotransferase System ◽  
Content Type ◽  
Metabolic Fluxes ◽  
Central Carbon

ABSTRACTTwo branches of the phosphoenolpyruvate-phosphotransferase system (PTS) operate in the soil bacteriumPseudomonas putidaKT2440. One branch encompasses a complete set of enzymes for fructose intake (PTSFru), while the other (N-related PTS, or PTSNtr) controls various cellular functions unrelated to the transport of carbohydrates. The potential of these two systems for regulating central carbon catabolism has been investigated by measuring the metabolic fluxes of isogenic strains bearing nonpolar mutations in PTSFruor PTSNtrgenes and grown on either fructose (a PTS substrate) or glucose, the transport of which is not governed by the PTS in this bacterium. The flow of carbon from each sugar was distinctly split between the Entner-Doudoroff, pentose phosphate, and Embden-Meyerhof-Parnas pathways in a ratio that was maintained in each of the PTS mutants examined. However, strains lacking PtsN (EIIANtr) displayed significantly higher fluxes in the reactions of the pyruvate shunt, which bypasses malate dehydrogenase in the TCA cycle. This was consistent with the increased activity of the malic enzyme and the pyruvate carboxylase found in the corresponding PTS mutants. Genetic evidence suggested that such a metabolic effect of PtsN required the transfer of high-energy phosphate through the system. The EIIANtrprotein of the PTSNtrthus helps adjust central metabolic fluxes to satisfy the anabolic and energetic demands of the overall cell physiology.IMPORTANCEThis study demonstrates that EIIANtrinfluences the biochemical reactions that deliver carbon between the upper and lower central metabolic domains for the consumption of sugars byP. putida. These findings indicate that the EIIANtrprotein is a key player for orchestrating the fate of carbon in various physiological destinations in this bacterium. Additionally, these results highlight the importance of the posttranslational regulation of extant enzymatic complexes for increasing the robustness of the corresponding metabolic networks.

scholarly journals d-2,3-Butanediol Production Due to Heterologous Expression of an Acetoin Reductase in Clostridium acetobutylicum

2011 ◽  
Vol 77 (8) ◽  
pp. 2582-2588 ◽  
Author(s):  
Marco A. J. Siemerink ◽  
Wouter Kuit ◽  
Ana M. López Contreras ◽  
Gerrit Eggink ◽  
John van der Oost ◽  
...  
Keyword(s):  
Experimental Data ◽  
Heterologous Expression ◽  
Metabolic Network ◽  
Clostridium Acetobutylicum ◽  
Clostridium Beijerinckii ◽  
Racemic Mixture ◽  
Gene Encoding ◽  
Content Type ◽  
Batch Cultures

ABSTRACTAcetoin reductase (ACR) catalyzes the conversion of acetoin to 2,3-butanediol. Under certain conditions,Clostridium acetobutylicumATCC 824 (and strains derived from it) generates bothd- andl-stereoisomers of acetoin, but because of the absence of an ACR enzyme, it does not produce 2,3-butanediol. A gene encoding ACR fromClostridium beijerinckiiNCIMB 8052 was functionally expressed inC. acetobutylicumunder the control of two strong promoters, the constitutivethlpromoter and the late exponentialadcpromoter. Both ACR-overproducing strains were grown in batch cultures, during which 89 to 90% of the natively produced acetoin was converted to 20 to 22 mMd-2,3-butanediol. The addition of a racemic mixture of acetoin led to the production of bothd-2,3-butanediol andmeso-2,3-butanediol. A metabolic network that is in agreement with the experimental data is proposed. Native 2,3-butanediol production is a first step toward a potential homofermentative 2-butanol-producing strain ofC. acetobutylicum.

scholarly journals Transport of d-Xylose in Lactobacillus pentosus, Lactobacillus casei, andLactobacillus plantarum: Evidence for a Mechanism of Facilitated Diffusion via the Phosphoenolpyruvate:Mannose Phosphotransferase System

1999 ◽  
Vol 181 (16) ◽  
pp. 4768-4773 ◽  
Author(s):  
Stéphane Chaillou ◽  
Peter H. Pouwels ◽  
Pieter W. Postma
Keyword(s):  
Dry Weight ◽  
Facilitated Diffusion ◽  
Xylose Metabolism ◽  
Phosphotransferase System ◽  
Gene Encoding ◽  
Lactobacillus Pentosus ◽  
Xylose Transport ◽  
Rate Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

ABSTRACT We have identified and characterized the d-xylose transport system of Lactobacillus pentosus. Uptake ofd-xylose was not driven by the proton motive force generated by malolactic fermentation and required d-xylose metabolism. The kinetics of d-xylose transport were indicative of a low-affinity facilitated-diffusion system with an apparent Km of 8.5 mM and aV max of 23 nmol min−1 mg of dry weight−1. In two mutants of L. pentosusdefective in the phosphoenolpyruvate:mannose phosphotransferase system, growth on d-xylose was absent due to the lack ofd-xylose transport. However, transport of the pentose was not totally abolished in a third mutant, which could be complemented after expression of the L. curvatus manB gene encoding the cytoplasmic EIIBMan component of the EIIMancomplex. The EIIMan complex is also involved ind-xylose transport in L. casei ATCC 393 andL. plantarum 80. These two species could transport and metabolize d-xylose after transformation with plasmids which expressed the d-xylose-catabolizing genes of L. pentosus, xylAB. L. casei and L. plantarum mutants resistant to 2-deoxy-d-glucose were defective in EIIMan activity and were unable to transportd-xylose when transformed with plasmids containing thexylAB genes. Finally, transport of d-xylose was found to be the rate-limiting step in the growth of L. pentosus and of L. plantarum and L. caseiATCC 393 containing plasmids coding for thed-xylose-catabolic enzymes, since the doubling time of these bacteria on d-xylose was proportional to the level of EIIMan activity.

scholarly journals Transcriptional analysis of differential carbohydrate utilization by Clostridium acetobutylicum

Microbiology ◽  
2010 ◽  
Vol 156 (11) ◽  
pp. 3478-3491 ◽  
Author(s):  
Matthew D. Servinsky ◽  
James T. Kiel ◽  
Nicole F. Dupuy ◽  
Christian J. Sund
Keyword(s):  
Clostridium Acetobutylicum ◽  
Dna Microarrays ◽  
Pentose Phosphate ◽  
Major Facilitator Superfamily ◽  
Transcriptional Analysis ◽  
Transcriptional Level ◽  
Phosphotransferase System ◽  
Carbohydrate Utilization ◽  
Major Facilitator ◽  
Pentose Sugars

Transcriptional analysis was performed on Clostridium acetobutylicum with the goal of identifying sugar-specific mechanisms for the transcriptional regulation of transport and metabolism genes. DNA microarrays were used to determine transcript levels from total RNA isolated from cells grown on media containing eleven different carbohydrates, including two pentoses (xylose, arabinose), four hexoses (glucose, mannose, galactose, fructose), four disaccharides (sucrose, lactose, maltose, cellobiose) and one polysaccharide (starch). Sugar-specific induction of many transport and metabolism genes indicates that these processes are regulated at the transcriptional level and are subject to carbon catabolite repression. The results show that C. acetobutylicum utilizes symporters and ATP-binding cassette (ABC) transporters for the uptake of pentose sugars, while disaccharides and hexoses are primarily taken up by phosphotransferase system (PTS) transporters and a gluconate : H+ (GntP) transporter. The transcription of some transporter genes was induced by specific sugars, while others were induced by a subset of the sugars tested. Sugar-specific transport roles are suggested, based on expression comparisons, for various transporters of the PTS, the ABC superfamily and members of the major facilitator superfamily (MFS), including the GntP symporter family and the glycoside-pentoside-hexuronide (GPH)-cation symporter family. Additionally, updates to the C. acetobutylicum genome annotation are proposed, including the identification of genes likely to encode proteins involved in the metabolism of arabinose and xylose via the pentose phosphate pathway.

Enzymes associated with metabolism of xylose and other pentoses by Prevotella (Bacteroides) ruminicola strains, Selenomonas ruminantium D, and Fibrobacter succinogenes S85

1992 ◽  
Vol 38 (5) ◽  
pp. 370-376 ◽  
Author(s):  
Allan Matte ◽  
Cecil W. Forsberg ◽  
Ann M. Verrinder Gibbins
Keyword(s):  
Xylose Isomerase ◽  
Sole Source ◽  
Pentose Phosphate ◽  
Binding Potential ◽  
Fibrobacter Succinogenes ◽  
Xylose Metabolism ◽  
Ruminal Bacteria ◽  
Selenomonas Ruminantium ◽  
Pentose Phosphate Cycle ◽  
Prevotella Ruminicola

Prevotella (Bacteroides) ruminicola strains B14 and S23 and Selenomonas ruminantium strain D used xylose as the sole source of carbohyrate for growth, whereas Fibrobacter succinogenes was unable to metabolize xylose. Prevotella ruminicola strain B14 exhibited transport activity for xylose. In contrast, F. succinogenes lacked typical xylose uptake activity but did exhibit low binding potential for the sugar. Prevotella ruminicola strains B14 and S23 as well as S. ruminantium D showed low xylose isomerase activities but higher xylulokinase activities, using assays that gave high activities for these enzymes in Escherichia coli. Xylose isomerase appeared to be produced constitutively in these ruminal bacteria, but xylulokinase was induced to varying degrees with xylose as the source of carbohydrate. Fibrobacter succinogenes lacked xylose isomerase and xylulokinase. All three species of ruminal bacteria possessed transketolase,xylulose-5-phosphate epimerase, and ribose-5-phosphate isomerase activities. Neither P. ruminicola B14 nor F. succinogenes S85 showed significant phosphoketolase activity. The data indicate that F. succinogenes is unable to either actively uptake or metabolize xylose as a result of the absence of functional xylose permease, xylose isomerase, and xylulokinase activities, although it and both P. ruminicola and S. ruminantium possess the essential enzymes of the nonoxidative branch of the pentose phosphate cycle. Key words: Fibrobacter succinogenes, Prevotella, Selenomonas, xylose metabolism, rumen bacteria, pentose phosphate cycle.

scholarly journals Important Metabolic Pathways and Biological Processes Expressed by Chicken Cecal Microbiota

2015 ◽  
Vol 82 (5) ◽  
pp. 1569-1576 ◽  
Author(s):  
Ondrej Polansky ◽  
Zuzana Sekelova ◽  
Marcela Faldynova ◽  
Alena Sebkova ◽  
Frantisek Sisak ◽  
...  
Keyword(s):  
Intestinal Tract ◽  
Xylose Isomerase ◽  
Membrane Receptors ◽  
Biological Processes ◽  
Phosphotransferase System ◽  
Content Type ◽  
Probiotic Strains ◽  
Cecal Microbiota ◽  
Acyl Coenzyme A ◽  
Butyrate Production

ABSTRACTThe gut microbiota plays important roles in its host. However, how each microbiota member contributes to the behavior of the whole population is not known. In this study, we therefore determined protein expression in the cecal microbiota in chickens of selected ages and in 7-day-old chickens inoculated with different cecal extracts on the day of hatching.Campylobacter,Helicobacter,Mucispirillum, andMegamonasovergrew in the ceca of 7-day-old chickens inoculated with cecal extracts from donor hens.Firmicuteswere characterized by ABC and phosphotransferase system (PTS) transporters, extensive acyl coenzyme A (acyl-CoA) metabolism, and expression ofl-fucose isomerase.Anaerostipes,Anaerotruncus,Pseudoflavonifractor,Dorea,Blautia, andSubdoligranulumexpressed spore proteins.Firmicutes(Faecalibacterium,Butyrivibrio,Megasphaera,Subdoligranulum,Oscillibacter,Anaerostipes, andAnaerotruncus) expressed enzymes required for butyrate production.Megamonas,Phascolarctobacterium, andBlautia(exceptions from the phylumFirmicutes) and allBacteroidetesexpressed enzymes for propionate production pathways. Representatives ofBacteroidetesalso expressed xylose isomerase, enzymes required for polysaccharide degradation, and ExbBD, TonB, and outer membrane receptors likely to be involved in oligosaccharide transport. Based on our data,Anaerostipes,Anaerotruncus, andSubdoligranulummight be optimal probiotic strains, since these represent spore-forming butyrate producers. However, certain care should be taken during microbiota transplantation because the microbiota may behave differently in the intestinal tract of a recipient depending on how well the existing communities are established.

scholarly journals Deletion ofPHO13, Encoding Haloacid Dehalogenase Type IIA Phosphatase, Results in Upregulation of the Pentose Phosphate Pathway in Saccharomyces cerevisiae

2014 ◽  
Vol 81 (5) ◽  
pp. 1601-1609 ◽  
Author(s):  
Soo Rin Kim ◽  
Haiqing Xu ◽  
Anastashia Lesmana ◽  
Uros Kuzmanovic ◽  
Matthew Au ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Molecular Mechanisms ◽  
Pentose Phosphate ◽  
Sequencing Analysis ◽  
Xylose Metabolism ◽  
Fermentation Inhibitors ◽  
Haloacid Dehalogenase ◽  
Content Type ◽  
Had Superfamily ◽  
Transcriptomic Level

ABSTRACTThe haloacid dehalogenase (HAD) superfamily is one of the largest enzyme families, consisting mainly of phosphatases. Although intracellular phosphate plays important roles in many cellular activities, the biological functions of HAD enzymes are largely unknown. Pho13 is 1 of 16 putative HAD enzymes inSaccharomyces cerevisiae. Pho13 has not been studied extensively, but previous studies have identifiedPHO13to be a deletion target for the generation of industrially attractive phenotypes, namely, efficient xylose fermentation and high tolerance to fermentation inhibitors. In order to understand the molecular mechanisms underlying the improved xylose-fermenting phenotype produced by deletion ofPHO13(pho13Δ), we investigated the response ofS. cerevisiaetopho13Δ at the transcriptomic level when cells were grown on glucose or xylose. Transcriptome sequencing analysis revealed thatpho13Δ resulted in upregulation of the pentose phosphate (PP) pathway and NADPH-producing enzymes when cells were grown on glucose or xylose. We also found that the transcriptional changes induced bypho13Δ required the transcription factor Stb5, which is activated specifically under NADPH-limiting conditions. Thus,pho13Δ resulted in the upregulation of the PP pathway and NADPH-producing enzymes as a part of an oxidative stress response mediated by activation of Stb5. Because the PP pathway is the primary pathway for xylose, its upregulation bypho13Δ might explain the improved xylose metabolism. These findings will be useful for understanding the biological function ofS. cerevisiaePho13 and the HAD superfamily enzymes and for developingS. cerevisiaestrains with industrially attractive phenotypes.

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