High impact information on XKS1

• The fungal L-arabinose pathway consists of five enzymes, aldose reductase, L-arabinitol 4-dehydrogenase, L-xylulose reductase, xylitol dehydrogenase, and xylulokinase [1].
• In recombinant S. cerevisiae expressing XYL1, XYL2, and XYL3, mRNA transcript levels for glycolytic, fermentative, and pentose phosphate enzymes did not change significantly on glucose or xylose under aeration or oxygen limitation [2].
• S. cerevisiae engineered for d-xylose utilization through the heterologous expression of genes for aldose reductase (XYL1), xylitol dehydrogenase (XYL2), and d-xylulokinase (XYL3 or XKS1) produce only limited amounts of ethanol in xylose medium [2].
• Multicopy and single-copy constructs with either XYL3 or XKS1, likewise under control of the TDH1 promoter, or with the native P. stipitis promoter were introduced into the recombinant S. cerevisiae [3].
• Uncontrolled XK expression in recombinant S. cerevisiae is inhibitory in a manner analogous to the substrate-accelerated cell death observed with an S. cerevisiae tps1 mutant during glucose metabolism [3].

Biological context of XKS1

• The selected transformant had approximately four copies of XYL3 per haploid genome and had moderate XK activity [3].
• This gene corresponds to the YGR194c open reading frame that we have previously described, and it is renamed now XKS1 [4].
• Data bank comparisons of the protein encoded by the XKS1 gene showed significant homology with different xylulokinases, indicating a possible role in xylulose phosphorylation [4].
• In addition to the geneticin resistance and ampicillin resistance genes that serve as dominant selectable markers, these plasmids also contain three xylose-metabolizing genes, a xylose reductase gene, a xylitol dehydrogenase gene (both from Pichia stipitis), and a xylulokinase gene (from Saccharomyces cerevisiae) [5].
• The ORF G7584 showed 35.8% identity with a hypothetical protein of Caenorhabditis elegans chromosome 3 [6].

Associations of XKS1 with chemical compounds

• Anaerobic xylose fermentation by recombinant Saccharomyces cerevisiae carrying XYL1, XYL2, and XKS1 in mineral medium chemostat cultures [7].
• Growth inhibition increased and ethanol yields from xylose decreased with increasing XK activity [3].
• Overexpression of XYL3 and XKS1 inhibited growth on xylose but did not affect growth on glucose even though XK activities were three times higher in glucose-grown cells [3].
• Specific xylulose consumption rate was enhanced by the increased specific XK activity, resulting from the introduction of the XKS1 into S. cerevisiae [8].
• However, overexpression of XKS1 shifted polyol formation from xylitol to arabinitol [9].

Regulatory relationships of XKS1

• Xylulokinase overexpression in two strains of Saccharomyces cerevisiae also expressing xylose reductase and xylitol dehydrogenase and its effect on fermentation of xylose and lignocellulosic hydrolysate [10].
• METHODS AND RESULTS: The cloned xylulokinase gene (XKS1) from S. cerevisiae was expressed under the control of the glyceraldehyde 3-phosphate dehydrogenase promoter and terminator [8].

Other interactions of XKS1

• The strain expressed XR, XDH, and XK activities of 0.4 to 0.5, 2.7 to 3.4, and 1.5 to 1.7 U/mg, respectively, and was stable for more than 40 generations in continuous fermentations [7].

Analytical, diagnostic and therapeutic context of XKS1

• Molecular cloning of XYL3 (D-xylulokinase) from Pichia stipitis and characterization of its physiological function [11].

References