Developmental changes of cholesterol ester hydrolases localized in myelin and microsomes of rat brain.

Abstract

AbstractWe Previously demonstrated two distinct cholesterol ester hydrolases in rat brain (Eto and Suzuki, 1971). One of the two hydrolases had a pH optimum of 6·6 and showed a bimodal subcellular distribution, in microsomes and myelin. A substantial activity of this enzyme was present in newborn rat brain. The activity remained relatively unchanged during the first 12 days and then increased sharply, concomitant with the period of active myelination (Eto and Suzuki, 1972a). The more recent investigation, however, clearly demonstrated that this pH 6·6 cholesterol ester hydrolase actually consists of two distinct cholesterol ester hydrolases, one primarily localized in microsomes and the other almost exclusively localized in the myelin sheath (Eto and Suzuki, 1972b, 1973). The microsomal hydrolase had a pH optimum of 6·0 and was activated by sodium taurocholate and Triton X‐100, particularly by the latter. The myelin enzyme had a pH optimum of 7·2. It was activated by sodium taurocholate but slightly inhibited by Triton X‐100. These new findings suggested that the previously reported developmental curve of the pH 6·6 cholesterol ester hydrolase was probably a composite of developmental changes of these two distinct cholesterol ester hydrolases. We report here the findings which confirm the above prediction and update the information regarding the developmental changes of the enzymes involved in cholesterol ester metabolism in rat brain.