Activities of both rat muscle and liver phosphofructokinases are significantly inhibited after a single ethanol intake in the dose of 2.5？g per kg of body weight. This inhibitory effect is indirect, since ethanol in concentration (50？mM) close to that established after 2.5？g per kg of body weight intake cannot decrease their activities in vitro. Inhibition of liver phosphofructokinase activity after the 5.0？g per kg ethanol intake may be direct, since liver phosphofructokinase activity decreases in vitro when ethanol is added to supernatants of rat liver tissue in 100？mM concentration. According to the results of molecular docking, ethanol at high concentrations can be bound by adenine-binding pocket of the allosteric ADP-binding site of liver phosphofructokinase (Asp543, Phe308, Phe538, and Phe671) and its activation by ADP can be blocked by C2H5OH molecule. Direct inhibition of muscle phosphofructokinase activity, probably due to the binding of ethanol to the similar ADP-binding site, is possible when the concentration of ethanol (500？mM) is much higher than the level which can be established in living cells. So, inhibition of muscle phosphofructokinase activity after a single 5.0？g per kg intake is indirect and probably linked with the inhibition of the enzyme by elevated citrate and phosphoenolpyruvate levels. 1. Introduction Phosphofructokinase catalyzes phosphorylation of fructose-6-phosphate to fructose-1,6-bisphosphate. This reaction is a key regulatory step in the glycolysis [1]. Phosphofructokinase activity is regulated through allosteric inhibition and activation. High ATP to ADP ratio inhibits phosphofructokinase and glycolysis as well [1]. Indeed, ADP (the product of the reaction) is an allosteric activator of the activity of that enzyme [2]. Phosphofructokinase is also activated by AMP and fructose-2,6-bisphosphate and inhibited by phosphoenolpyruvate and citrate [3]. Mammalian phosphofructokinase is a tetramer. There are three genes encoding monomers of phosphofructokinase. They are designated as muscle, liver, and platelet phosphofructokinases. The muscle enzyme is a homotetramer (composed of four identical muscle subunits) [1]. Liver also expresses predominantly homotetramer composed of four liver subunits [1]. Ethanol can be found in 163 entries in the Protein Data Bank (http://www.pdb.org/). It can interact with many proteins being a part of the solvent. Alcohol dehydrogenases bind (and metabolize) ethanol specifically [1]. Ethanol also binds α7-nAChRs (nicotinic acetylcholine receptors) as an agonist [4], GABA receptors
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