Expression of Escherichia coli otsA in a Saccharomyces cerevisiae tps1 mutant restores trehalose 6-phosphate levels and partly restores growth and fermentation with glucose and control of glucose influx into glycolysis

The TPS1 gene, encoding trehalose-6-phosphate synthase (TPS), exerts an ess ential control on the influx of glucose into glycolysis in the yeast Saccha romyces cerevisiae. The deletion of TPS1 causes an inability to grow on glu cose because of a hyperaccumulation of sugar phosphates and depletion of AT P and phosphate, We show that expression of the Escherichia coli homologue, otsA, in a yeast tpsl mutant results in high TPS activity. Although the tr ehalose 6-phosphate (Tre6P) level durning exponential growth on glucose was at least as high as in a wildtype yeast strain, growth on glucose was only partly restored and the lag phase was much longer. Measurement of the glyc olytic metabolites immediately after the addition of glucose showed that in spite of a normal Tre6P accumulation there was still a partial hyperaccumu lation of sugar phosphates. Strong elevation of the Tre6P level by the addi tional deletion of the TPS2 gene, which encodes Tre6P phosphatase, was not able to cause a strong decrease in the sugar phosphate levels in comparison with the wild-type strain. In addition, in chemostat experiments the short -term response to a glucose pulse was delayed, but normal metabolism was re gained over a longer period. These results show that Tre6P synthesis from a heterologous TPS enzyme can to some extent restore the control of glucose influx into glycolysis and growth on glucose in yeast. However, they also i ndicate that the yeast TPS enzyme, as opposed to the E. coli otsA gene prod uct, is able to increase the efficiency of the Tre6P control on glucose inf lux into yeast glycolysis.