Abstract
The role of AMP deaminase (EC 3.5.4.6) reaction in the stimulation of the regulatory enzymes of glycolysis was investigated using permeabilized yeast cells. 1) The addition of polyamine activated AMP deaminase in situ, resulting in the subsequent increase in ammonium production, which can stimulate the activity of 6-phosphofructokinase (EC 2.7.1.11) and pyruvate kinase (EC 2.7.1.40). 2) Zn2+ inhibited AMP deaminase activity, followed by a decrease in ammonium ion concentration which reduced the activity of phosphofructokinase. 3) Polyamine and Zn2+ did not activate or inhibit directly the activity of phosphofructokinase and pyruvate kinase. 4) A simple Michaelis-Menten relationship was observed between the various levels of ammonium ion and of fructose 1,6-biphosphate formed in situ, indicating that phosphofructokinase activity or glycolytic flux was dependent upon the level of ammonium produced through the action of AMP deaminase. 5) The increase in Pi concentration resulted in the decreased magnitude of activation by NH4+ and marked stimulation by Pi itself of phosphofructokinase, and further reduced the production of NH4+ through the inhibition of AMP deaminase, suggesting that phosphofructokinase activity may not be regulated by the level of NH4+ but by Pi concentration under conditions of increased Pi levels. The AMP deaminase-ammonium system shows a regulatory function in glycolysis of yeast cells in the presence of physiological Pi levels, whereas glycolysis may be principally controlled by Pi level under the conditions of elevated Pi concentration. Polyamines may play a part in the stimulation of glycolysis through the elevated level of ammonium ion under the conditions of increased ATP utilization during cell proliferation, and can participate in the catabolic processes as well as anabolic processes through the stimulation of the AMP deaminase-ammonium system.
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