The active site and the phospholipid activation of rat liver lysosomal lipase are not stereospecific

The stereochemical specificity of lysosomal lipase of rat liver was investigated using enantiomeric triacylglycerol analogs, sn-1-alkyl-2,3-diacylglycerol and sn-3-alkyl-1,2-diacylglycerol as substrates. Lysosomal lipase utilized both substrates with equal rates. The dependence of the activity of lysosomal lipase on the stereoconfiguration of activating acidic phospholipid was also studied. Our results showed that both sn-3-phospholipids (diphosphatidylglycerol, phosphatidylserine) and sn-1-phospholipids (bis(monoacylglycero)phosphate (BMP) were efficient activators of this enzyme and thus the stereochemical configuration of the activating phospholipid is not important. Accordingly, the rat liver lysosomal lipase lacks stereospecificity with respect to both the triacylglycerol substrate and the acidic phospholipid activator.