The significance of genetic regulation in the control of glycolysis in Saccharomyces cerevisiae
The aim of this work was to establish the relative contribution of genetic regulation of the PYK1, PFK1 and PFK2 genes to the control of glycolysis. A series of isogenic mutant strains were constructed where the promoters and 5' untranslated sequences of the PYK1, PFK1 and PFK2 genes were replaced with those from PGK1. In addition , a second series of mutant strains were constructed where synthesis of Pyk1p and Pflkp was driven by the PGK1Δuas promoter. These latter series of mutants were designed to contain weak expression of Pyklp and Pflkp. Analysis of UKC1 (PGK::PYK1) in shake flask cultures revealed similar growth rates on glucose and on lactate and similar rates of ethanol production and glucose consumption to those of the wild-type strain. This suggested that the native genetic regulation did not appear to play a significant role in the control of glycolysis. Nonetheless, analysis of this strain in the fermentor revealed that genetic regulation of PYK1 may be important in co-ordinating Pyk1p synthesis, under the conditions studied. Analysis of YKC11 (PGKΔuas::PYK1) in both shake flask and fermentor experiments showed that genetic control was important in maintaining Pyk1p levels in order to sustain glycolytic flux. Shake flask analysis of the single and double PFK mutants under the control of the PGK1 promoter revealed that the genetic regulation of the PFK1 and PFK2 genes did not appear to be important in the control of glycolysis. Weak expression of the PFK1 and PFK2 genes, under the control of the PGKΔuas promoter showed the importance of genetic regulation in maintaining Pflkp levels to support glycolytic flux, under the conditions studied.