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Characterization of non-oxidative transaldolase and transketolase enzymes in the pentose phosphate pathway with regard to xylose utilization by recombinant Saccharomyces cerevisiae

Paper ID Volume ID Publish Year Pages File Format Full-Text
17313 42659 2012 10 PDF Available
Title
Characterization of non-oxidative transaldolase and transketolase enzymes in the pentose phosphate pathway with regard to xylose utilization by recombinant Saccharomyces cerevisiae
Abstract

The activity of transaldolase and transketolase, key enzymes in the non-oxidative pentose phosphate pathway, is rate-limiting for xylose utilization in recombinant Saccharomyces cerevisiae. Overexpression of TAL1 and TKL1, the major transaldolase and transketolase genes, increases the flux from the pentose phosphate pathway into the glycolytic pathway. However, the functional roles of NQM1 and TKL2, the secondary transaldolase and transketolase genes, especially in xylose utilization, remain unclear. This study focused on characterization of NQM1 and TKL2, together with TAL1 and TKL1, regarding their roles in xylose utilization and fermentation. Knockout or overexpression of these four genes on the phenotype of xylose-utilizing S. cerevisiae strains was also examined. Transcriptional analysis indicated that the expression of TAL1, NQM1, and TKL1 was up-regulated in the presence of xylose. A significant decrease in both growth on xylose and xylose-fermenting ability in tal1Δ and tkl1Δ mutants confirmed that TAL1 and TKL1 are essential for xylose assimilation and fermentation. Gene disruption analysis using a tkl1Δ mutant revealed that TKL1 is also required for utilization of glucose. Growth on xylose and xylose-fermenting ability were slightly influenced by deletion of NQM1 or TKL2 when xylose was used as the sole carbon source. Moreover, the rate of xylose consumption and ethanol production was slightly impaired in TKL1- and TKL2-overexpressing strains. NQM1 and TKL2 may thus play a physiological role via an effect on the non-oxidative pentose phosphate pathway in the xylose metabolic pathway, although their roles in xylose utilization and fermentation are less important than those of TAL1 and TKL1.

► Little is known about the molecular mechanisms of the NQM1 and TKL2 encoded proteins. ► We characterize NQM1, TKL2, TAL1, and TKL1, regarding their roles in xylose utilization. ► Expression of TAL1, NQM1, and TKL1 is up-regulated in the presence of xylose. ► TAL1 and TKL1 are necessary for both growth on xylose and for fermentation of xylose. ► The fermentation rate of xylose is impaired in TKL1- and TKL2-overexpressing strains.

Keywords
XR, xylose reductase; XDH, xylitol dehydrogenase; XK, xylulokinase; PPP, pentose phosphate pathway; TAL, transaldolase; TKL, transketolase; GDH, glycerol 3-phosphate dehydrogenase; TIM, triosephosphate isomerase; DCW, dry cell weightTransaldolase; Transke
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Characterization of non-oxidative transaldolase and transketolase enzymes in the pentose phosphate pathway with regard to xylose utilization by recombinant Saccharomyces cerevisiae
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Publisher
Database: Elsevier - ScienceDirect
Journal: Enzyme and Microbial Technology - Volume 51, Issue 1, 10 June 2012, Pages 16–25
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us