Kinetics and inhibition of lipid exchange catalyzed by plasma cholesteryl ester transfer protein (lipid transfer protein).

The cholesteryl ester transfer protein-catalyzed cholesteryl ester transfer is inhibited by two compounds identified by a large-scale screening of cholesterol backbone-containing molecules. Kinetic analysis shows that U-95,594, an amino steroid, inhibits competitively the cholesteryl ester transfer protein-catalyzed transfer of both cholesteryl esters and triglycerides, as well from high-density lipoproteins as from synthetic microemulsions. In contrast, U-617, an organomercurial derivative of cholesterol, inhibits competitively the transfer of cholesteryl ester from either donor but is without any effect on triglyceride transfer. In addition to the rapid, competitive inhibition of cholesteryl ester transfer, U-617 also slowly and reversibly reacts with cholesteryl ester transfer protein to produce an additional 10-fold decrease in cholesteryl ester transfer activity but, again, without effect on triglyceride transfer.