Purification and properties of cholesterol ester hydrolase from human aortic intima and media.

1. Cholesterol ester hydrolase of human aortic intima and media was isolated and purified about 650-fold with 10-15% recovery of the original activity by sequential precipitation with 35% acetone, gel filtration on Sephadex G-75 and DEAE-cellulose column chromatography. 2. Two pH optima of 4.5-5.0 and 7.0-7.5 were consistently observed for the partially purified cholesterol ester hydrolase of human aortic intima and media. 3. In the system used in the present study, the increasing concentration of emulsifiers, sodium taurocholate and phosphatidylcholine, inhibited the activity of the neutral enzymes but not on the acid enzymes. On the contrary, reaction products, cholesterol and oleic acid, were much more inhibitory on the acid enzymes than on the neutral ones. 4. Results of studies on the effect of presentation of substrate on the enzyme activity and on the difference between acid and neutral enzymes are also discussed.