HYDROLYSIS OF RETINYL ESTERS IN RAT-LIVER - DESCRIPTION OF A LYSOSOMAL ACTIVITY

When incorporated into liposomes made of phospholipids, retinyl palmit ate is an adequate substrate for an acidic REH (aREH). In rat liver, t his activity is mainly localized in the lysosomal fraction. Kinetic pa rameters have been determined for retinyl palmitate (K-m = 315 mu M; m aximal rate = 22.1 nmol retinol/h per mg protein). The aREH activity i s different from the lysosomal acidic cholesteryl ester hydrolase (aCE H): cholesteryl oleate does not inhibit aREH activity, neither do some aCEH specific inhibitors, and aREH does not hydrolyse cholesteryl est er. Involvement of aREH in the hydrolysis of lipid droplets retinyl es ters in fat storing cells is discussed.