Open AccessA hysteretic cycle in glucose 6‐phosphate metabolism observed in a cell‐free yeast extract
Author(s) -
ESCHRICH Klaus,
SCHELLENBERGER Wolfgang,
HOFMANN Eberhard
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb15452.x
Subject(s) - phosphoenolpyruvate carboxykinase , yeast , pyruvate kinase , substrate (aquarium) , fructose , glucose 6 phosphate , glycolysis , biochemistry , phosphofructokinase , enzyme , biophysics , chemistry , biology , ecology
The dynamics of a partial glycolytic reaction sequence which converts glucose 6‐phosphate to triose phosphates is described. The study was performed with cell‐free extracts from baker's yeast harvested in the logarithmic and stationary growth phases. The experiments are based on a flow‐through reactor supplied with the desalted cell‐free extract as well as glucose 6‐phosphate, ATP and phospho enol pyruvate. In the reaction system the quasi‐irreversible reactions catalyzed by 6‐phosphofructo‐1‐kinase, pyruvate kinase, and fructose‐1,6‐bisphosphatase are involved. When substrate is supplied continuously, only stable stationary states can be observed. With transient perturbations of the substrate supply, multiple stationary states appear. Cyclic transitions between unique stable stationary states were induced by appropriate changes of the rate of substrate supply. A hysteretic cycle could then be demonstrated when, during reverse transitions, a parameter region of multistability was passed. The presence (in resting yeast) or absence (in growing yeast) of fructose‐1,6‐bisphosphatase did not significantly influence the dynamic capabilities of the investigated reation sequence. The kinetic properties of the cell‐free extracts fit mathematical models developed for in vitro systems reconstituted from purified enzymes.