© 1977 Oxford University Press
RESEARCH-ARTICLE |
Effects of Chloride Salts at High Concentrations on Glycolysis in vitro
Agronomy Department, University of Western Australia Nedlands, W.A. 6009, W. Australia
KC1, at 200 mM, decreased rates of glycolysis, in vitro, in the steady state and also increased the time required to reach the steady state of CO2 and ethanol formation after glucose addition.
KCl at 200 mM increased concentrations of fructose-1,6-diphosphate and decreased concentrations of pyruvate, at all times between 3 and 120 min after glucose addition. At early times after glucose addition, 200 mM KCl decreased concentrations of triose phosphates and 3-phos-phoglycerate. However, at later times, concentrations of these two intermediates became higher at 200 mM KC1 than at low Cl–; with triose phosphates this occurred for the first time at 20 min and with 3-phosphoglyeerate at 60 min after glucose addition. These and other experiments, including one using the crossover theorem of Chance, strongly suggested that the increased concentrations of fructose- 1,6-diphosphate and triose phosphates alleviated severe KCl inhibitions of enzymes catalysing reactions in the conversion of fructose-l,6-diphosphate to 1,3-diphosphoglycerate. Similar phenomena occurred for other parts of the pathway. Thus, the glycolytic sequence responded to high KCl and NaCl concentrations in a manner predicted from earlier published experiments with single enzymes, in which KCl and NaCl inhibitions were much smaller at high than at low substrate concentrations.
For the steady state, addition of purified enzymes showed that high KCl reduced glycolysis, at least partly by persistent inhibitions of glyceraldehyde-3-phosphate dehydrogenase and/or aldolase.
Overall, the data suggest that high KCl and NaCl concentrations have two main effects: (1) a transient reduction in rate of glycolysis—this effect disappears when substrates of certain enzymes have increased above the initial low levels; and (2) inhibitions which persist despite high intermediate concentrations, i.e. inhibitions which occur even in the ‘steady state’. The relevance of these in vitro data to in vivo responses at high salt concentrations is briefly discussed.