Flux regulation in glycogen-induced oscillatory glycolysis in cell-free extracts of Saccharomyces carlsbergensis |
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Authors: | Sreekantha Babu Jonnalagadda Joern-Ullrich Becker EE Selkov Augustin Betz |
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Institution: | 2. Institute of Botany, University of Bonn, Kirschallee 1, D-5300 Bonn 1, Germany;1. Institute of Biophysics of the USSR, Academy of Sciences, 142292 Pushchino, U.S.S.R. |
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Abstract: | To localise the controlling point of the glycolytic system, the temporal changes of concentrations of glycolytic intermediates have been analysed after addition of glycogen to a substrate-depleted yeast extract. Three sequential metabolic states are clearly observable: a transition state at which there is continuous accumulation of the intermediates before the glyceraldehydephosphate dehydrogenase (GAPDH, EC 1.2.1.12) step; a stationary state with all glycolytic intermediates having concentrations oscillating at nearly stationary mean values; and a depletion state at which the intermediates before the GAPDH step are being depleted due to the exhaustion of glycogen. In all these states, the mean ethanol production rate and the concentration of ATP and the intermediates beyond the GAPDH-step are maintained fairly constant, while the glycogen consumption rate and intermediate concentrations of the upper part of the glycolytic system change considerably: the glycogen consumption rate varies 4-fold and fructose-bis-phosphate concentration more than 10-fold. Doubling of the initial glycogen concentration and the addition of a great excess of fructose-bis-phosphate do not affect the ethanol production rate and the mean glycerate-3-phosphate (3-PGA) and pyruvate levels. By contrast, ethanol production was accelerated by an increase of the net ATP consumption rate resulting from either the addition of apyrase or by substitution of trehalose for glycogen. Neither the mean absolute ATP level nor the adenylate energy charge were measurably affected, however all this data can be interpreted in terms of a very strong stoichiometric regulation and stabilization of the lower part of the glycolytic system. |
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Keywords: | DAP dihydroxyacetone phosphate FBP fructose-1 6-bis-phosphate F6P fructose-6-phosphate GAP glyceraldehyde-3-phosphate GAPDH glyceraldehydephosphate dehydrogenase (EC 1 2 1 12) G6P glucose-6-phosphate PEP phospho-enol-pyruvate PFK phosphofructokinase (EC 2 7 1 11) 2-PGA glycerate-2-phosphate 3-PGA glycerate-3-phosphate PGK phosphoglycerate kinase (EC 2 7 2 3) |
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