The Influence of Ethanol on Pyruvate Kinases Activity in Vivo, in Vitro, in Silico

Abstract

The influence of ethanol on enzymatic activities of muscle and liver pyruvate kinases has been studied in rats in series of in vivo and in vitro experiments accompanied by in silico study. Activity of muscle pyruvate kinase significantly decreased in experiments on acute alcohol intoxication (5.0g/kg of body weight), during chronic alcohol consumption (3.5g/kg of body weight 2 times a day for 14 and 28 days) and during the abstinence after the period of alcohol consumption (5.0g/kg of body weight 2 times a day for 5 days). Activity of liver pyruvate kinase was not decreased in rats after the period of alcohol consumption (5.0g/kg of body weight 2 times a day for 5 days) and during chronic alcohol consumption (3.5g/kg of body weight 2 times a day for 28 days). It even became significantly higher during the chronic alcohol consumption (3.5g/kg of body weight 2 times a day) lasting for 14 days. Inhibitory effect of alcohol bolus on activities of both pyruvate kinases should be linked with certain indirect mechanisms, since direct inhibitory effect was seen in vitro only after the addition of 500 mM ethanol to the rat muscle and liver supernatants. Since lactate dehydrogenase is used in a coupled assay for pyruvate kinase activity estimation we approved that 500mM ethanol did not inhibit lactate dehydrogenase activity in human plasma. Direct inhibition of pyruvate kinases activities should be due to the ability of ethanol to bind amino acid residues from the known allosteric site for alanine binding on muscle and liver pyruvate kinases shown by us with the help of molecular docking. Indirect activation of liver pyruvate kinase can be explained by the increase of glucose blood levels in rats during alcohol consumption promoting dephosphorylation of the enzyme as well as expression of the gene coding for it, and the decrease of alanine concentration in liver.