The activity and properties of a hepatic acid cholesteryl ester hydrolase obtained from rats of different age groups.

The activity of lysosomal acid cholesteryl ester hydrolase (acid CEH, EC 3.1.1.13) in rat liver was determined at 3, 5, 7, 10 and 20 wk following birth. The levels of acid CEH activity showed a marked decrease as rats grew older, whereas those of other lysosomal marker enzymes, such as acid phosphatase, beta-glucuronidase and cathepsin B and D, showed only a slight decrease. On the other hand, acid CEH activity was detected in all subcellular fractions obtained from rat liver, but the enzyme activity in these fractions did not show the age-related decrease observed in the lysosomal fraction. The results presented here suggest that the marked alteration of lysosomal acid CEH activity that accompanies aging may be related to its possible involvement in the regulation of cholesterol concentration in rat liver.