Diacylglycerol breakdown in plasma membrane of rat intestinal epithelial cells Effect of E. coli heat‐stable toxin

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Abstract
Rat intestinal epithelial cells were isolated and the activity of the enzyme diacylglycerol lipase (DG lipase, EC 3.1.1.3) was investigated. When cells were treated with Escherichia coli heat-stable toxin (ST) liberation of endogenous glycerol and fatty acids was observed. The enzyme responsible for this effect could be demonstrated to be a DG lipase by using specific substrates. It was found that the activity of DG lipase was increased 5–6-fold with the substrates diolein and 1,2-dioleyl-rac-glycerol and triolein being neutral lipid insensitive to DG lipase. ST had no direct effect on the DG lipase. The enzyme DG lipase was activated via a chain reaction due to the hydrolysis of phosphatidylinositol (PI) by the enzyme PI-specific phospholipase C stimulated by ST.