Lipolysis of Fluorescein and Eosin Esters. Kinetics of Hydrolysis

摘要

The enzymatic activity of steapsin lipase, porcine pancreas, wheat germ lipase, and acylase was assayed using the diacetyl, dipropionyl, dichloropropionyl, dibutyryl, divaleryl, and dicaproyl esters of fluorescein and the diacetyl, dipropionyl, and dibutyryl esters of eosin as substrates. The kinetic and thermodynamic parameters associated with the hydrolysis of the esters by the enzymes were determined. In addition, the action of sodium taurocholine on the enzymes was investigated by using soluble substrates, thereby eliminating any effect on an insoluble substrate. The eosin esters hydrolyzed extremely slowly in the presence of enzyme, even at pH's as high as 10.0. The hydrolysis rate of the fluorescein esters by all enzymes except porcine pancreas decreased in the order: acetate>propionate>butyrate>valerate>caproate. With porcine pancreas, divalerate and dicaproate had a higher hydrolysis rate than the dibutyrate. The order of activity is porcine pancreas>acylase>steapsin>wheat germ. Sodium taurocholate increased the rate of chymotrypsin hydrolysis of the fluorescein esters. No effect on lipase hydrolysis was observed, indicating that the probable effect of taurocholate in lipolytic hydrolysis is in making the substrate soluble. (Author)