INHIBITION OF RAT-LIVER RETINYL PALMITATE HYDROLASE ACTIVITY BY ETHER ANALOGS OF CHOLESTERYL ESTERS AND ACYLGLYCERIDES

In previous studies, retinyl palmitate hydrolase activity in rat liver was partly characterized and was found to correlate and to partially copurify with hydrolytic activities against cholesteryl oleate and triolein. Relationships between these 3 lipid ester hydrolase activities were further explored by use of nonhydrolyzable ether analogs of cholesteryl esters and acylglycerides. Cholesteryl ether analogs were potent inhibitors of all 3 hydrolase activities with relative potencies for the series of ethers of: linoleyl > oleyl = palmitoyl > n-butyl = n-propyl > ethyl = methyl. Retinyl palmitate hydrolase activity was most strongly inactivated by this series of analogs, with 48-86% of the activity inhibited at cholesteryl ether levels of 1 .mu.M. The acylglyceride ether analogs were much weaker inhibitors of the 3 hydrolase activities, with the triolein, diolein and dipalmitin analogs showing similar inhibitory potencies, greater than that of the monolein and monopalmitin analogs. The potential usefulness of ether analogs of cholesteryl esters and acylglycerides for exploring some of the characteristics of lipid ester hydrolase activities was demonstrated.