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Pearce AK, Crimmins K, Groussac E, Hewlins MJE, Dickinson JR, Francois J, Booth IR, Brown AJP. Pyruvate kinase (Pyk1) levels influence both the rate and direction of carbon flux in yeast under fermentative conditions. MICROBIOLOGY (READING, ENGLAND) 2001; 147:391-401. [PMID: 11158356 DOI: 10.1099/00221287-147-2-391] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Yeast phosphofructo-1-kinase (Pf1k) and pyruvate kinase (Pyk1) are allosterically regulated enzymes that catalyse essentially irreversible reactions in glycolysis. Both the synthesis and activity of these enzymes are tightly regulated. To separate experimentally the control of Pf1k and Pyk1 synthesis from their allosteric regulation, a congenic set of PFK1, PFK2 and PYK1 mutants was constructed in which these wild-type coding regions were driven by alternative promoters. Mutants carrying PGK1 promoter fusions displayed normal rates of growth, glucose consumption and ethanol production, indicating that the relatively tight regulation of Pyk1 and Pf1k synthesis is not essential for glycolytic control under fermentative growth conditions. Mutants carrying fusions to an enhancer-less version of the PGK1 promoter (PGK1(Delta767)) expressed Pyk1 and Pf1k at about 2.5-fold lower levels than normal. Physiological and metabolic analysis of the PFK1 PFK2 double mutant indicated that decreased Pf1k had no significant effect on growth, apparently due to compensatory increases in its positive effector, fructose 2,6-bisphosphate. In contrast, growth rate and glycolytic flux were reduced in the PGK1(Delta767)-PYK1 mutant, which had decreased Pyk1 levels. Unexpectedly, the reduced Pyk1 levels caused the flow of carbon to the TCA cycle to increase, even under fermentative growth conditions. Therefore, Pyk1 exerts a significant level of control over both the rate and direction of carbon flux in yeast.
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Affiliation(s)
- Amanda K Pearce
- Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1
| | - Kay Crimmins
- Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1
| | - Evelyne Groussac
- Centre de Bioingenierie Gilbert Durand, UMR-CNRS 5504 UR-INRA 792, Département de Génie Biochimique et Alimentaire, Institut National des Sciences Appliquées, 31077 Toulouse Cedex 04, France2
| | - Michael J E Hewlins
- Department of Chemistry, Cardiff University, PO Box 912, Cardiff CF10 3TB, UK3
| | - J Richard Dickinson
- Cardiff School of Biosciences, Cardiff University, PO Box 915, Cardiff CF10 3TL, UK4
| | - Jean Francois
- Centre de Bioingenierie Gilbert Durand, UMR-CNRS 5504 UR-INRA 792, Département de Génie Biochimique et Alimentaire, Institut National des Sciences Appliquées, 31077 Toulouse Cedex 04, France2
| | - Ian R Booth
- Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1
| | - Alistair J P Brown
- Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK1
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Petit T, Diderich JA, Kruckeberg AL, Gancedo C, Van Dam K. Hexokinase regulates kinetics of glucose transport and expression of genes encoding hexose transporters in Saccharomyces cerevisiae. J Bacteriol 2000; 182:6815-8. [PMID: 11073928 PMCID: PMC111426 DOI: 10.1128/jb.182.23.6815-6818.2000] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glucose transport kinetics and mRNA levels of different glucose transporters were determined in Saccharomyces cerevisiae strains expressing different sugar kinases. During exponential growth on glucose, a hxk2 null strain exhibited high-affinity hexose transport associated with an elevated transcription of the genes HXT2 and HXT7, encoding high-affinity transporters, and a diminished expression of the HXT1 and HXT3 genes, encoding low-affinity transporters. Deletion of HXT7 revealed that the high-affinity component is mostly due to HXT7; however, a previously unidentified very-high-affinity component (K(m) = 0.19 mM) appeared to be due to other factors. Expression of genes encoding hexokinases from Schizosaccharomyces pombe or Yarrowia lipolytica in a hxk1 hxk2 glk1 strain prevented derepression of the high-affinity transport system at high concentrations of glucose.
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Affiliation(s)
- T Petit
- Instituto de Investigaciones Biomédicas Alberto Sols, 28029 Madrid, Spain
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Current awareness on yeast. Yeast 2000. [DOI: 10.1002/1097-0061(20000115)16:1<89::aid-yea563>3.0.co;2-h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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