earticle

영어

P. stipitis, the best known xylose fermenting yeast, has been served as a gene source for metabolic engineering of xylose fermentation in S. cerevisiae. Specifically, three genes (XYL1, XYL2, and XYL3) coding for the xylose metabolic pathway enzymes (xylose reductase, xylitol
dehydrogenase, and xyluokinase) have been introduced into S. cerevisiae. The resulting recombinant S. cerevisiae strains were able to assimilate xylose as a carbon source, but did not produce ethanol with high yields. Accumulated results from prior studies suggested that simultaneous perturbation of multiple genes might be required to facilitate high yield
xylose fermentation in S. cerevisiae. In order to identify such a set of gene targets enhancing xylose fermentation, we investigated the levels of mRNA transcripts of P. stipitis grown under four different conditions through EST analysis. We discovered two notable features in the gene
expression profiles. First, transcripts of glucose-6-phsphate dehydrogenase (GND1), transketolase (TKT1), and transaldolase (TAL1), involved in the pentose phosphate pathway, are strongly induced on xylose. Second, the expression of a NAD-specific glutamate
dehydrogenase (GDH2) is elevated on xylose under oxygen limited conditions. These results suggest that higher capacity of the pentose pathway and a cofactor regeneration system are necessary for efficient maintenance of xylose metabolism.