Glucosidase and glucocerebrosidase activity in subcellular fractions of rat spleen.

Abstract

The glucocerebrosidase system was the first of the sphingolipid hydrolysing enzymes in which a heat stable factor has been shown to increase the enzymatic activity. Ho and her associates (1,2,3) have demonstrated that the heat stable factor or activator protein was present in the spleens of Gaucher patients and occured predominantly in the cytosol. It was devoid of enzymatic activity but associated with the catalytic protein found in normal spleen to render active enzyme. The activator stimulated both β -glucosidase and β -glucocerebrosidase activities. The Gaucher spleen effector was also active on lucocerebrosidase of calf spleen (4). Using purified enzyme from human placenta, it also increased the rate of hydrolysis of 4 methylumbelliferyl- β -glucoside but not of glucocerebroside at the pH optimum of the enzyme (5). The tacit assumption of these studies was that the heat stable factor found in Gaucher spleen was also present in normal liver and spleen. The difference was assumed to be quantitative — about 10–15 times more heat stable factor was present in Gaucher spleen than in normal spleen. Ho also suggested that some effector may already be bound to the membrane.