Mucopolysaccharidosis: Secondarily Induced Abnormal Distribution of Lysosomal Isoenzymes

Abstract

Total activities of acid hydrolases in liver of two patients with mucopolysaccharidosis are decreased for β-galactosidase, α-galactosidase, and arylsulfatase A; total activities of four other hydrolases are normal or increased. The isoenzyme distribution of five hydrolases (β-glucuronidase, α-glucosidase, β- galactosidase, N-acetyl-β-glucosaminidase, and α-galactosidase) is ábnormal in that the isoelectric points (by isoelectric focusing) of these enzymes are more acid than in control liver. Along with the isoenzyme abnormalities different kinds of glycolipids were stored in kidney, liver, and brain. The isoenzyme abnormalities can be reproduced in vitro by addition of chondroitin sulfate to a homogenate of normal liver, suggesting that stable binding occurs between mucopolysaccharides and the hydrolase molecules. After the addition of chondroitin sulfate, the total activity of β-galactosidase is inhibited, whereas other hydrolases are affected only slightly or not at all.