Stimulatory effect of phospholipase A 2 treatment on glucose utilization in human erythrocytes

Abstract

We examined whether modification of membrane phospholipids of human erythrocytes by hydrolysis with phospholipase A 2 (PLA 2 from bee venom) would affect glucose utilization, chosen as a typical model of intracellular metabolism, and, if so, intended to clarify the mechanism of the alteration of glycolysis. Treatment of erythrocytes with PLA 2 induced a marked shape change (i.e., crenation) and significantly increased the rate of lactate production from glucose. Available evidence indicated that there is no relevance of this cell-shape change to the alteration of glycolysis. The lack of a detectable effect of papain treatment on glycolysis in PLA 2-treated cells suggested that the increase in glycolysis by PLA 2 treatment might not be caused by the conformational change of band-3 protein through modulation of membrane phospholipids. The result of the measurement of lactate production in the presence and absence of ouabain did not support the idea that hydrolysis of phospholipids by PLA 2 treatment makes plasma membranes leaky to Na + and consequently enhances glycolysis through activation of Na + K +- ATPase . The action of PLA 2 on glycolysis was abolished by extraction of free fatty acids in the cell membrane with bovine serum albumin. Loading erythrocytes with free fatty acid (oleic acid, linoleic acid, or arachidonic acid) caused a significant increase in glycolysis. Analysis of glycolytic intermediates suggested that the enhancement of glycolysis was induced by activation of 6-phosphofructokinase. The data, thus, indicate that treatment of human erythrocytes with PLA 2 significantly accelerates glucose utilization and suggest that the stimulation of glycolysis is caused by activation of 6-phosphofructokinase through liberation of free fatty acids of membrane phospholipids by PLA 2.