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. The present studies were designed to further explore relationships between these three lipid ester hydrolase activities, by use of non-hydrolyzable ether analogs of cholesteryl esters and acylglycerides. Cholesteryl ether analogs were potent inhibitors of all three hydrolase activities with relative potencies for the series of ethers of: linoleyl greater than oleyl = palmitoyl greater than n-butyl = n-propyl greater than 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 microM. The acylglyceride ether analogs were much weaker inhibitors of the three hydrolase activities, with the triolein, diolein and dipalmitin analogs showing similar inhibitory potencies, greater than that of the monolein and monopalmitin analogs. The data demonstrate the potential usefulness of ether analogs of cholesteryl esters and acylglycerides for exploring some of the characteristics of lipid ester hydrolase activities.