Urinary Excretion of Acid Hydrolases in Disease

Methods were devised for the assay in urine of four acid hydrolases, β-galactosidase, α-mannosidase, N-acetyl-β-glucosaminidase, and -glucuronidase. Highest activities were obtained by assay directly on centrifuged urine. In gel filtration and isoelectric focusing experiments, these enzymes had properties in the urine very similar to those in the kidneys, with the exception of N-acetyl-β-glucosaminidase B, which had only a low activity in the urine. The following findings support the theory that the enzymes derive from the kidneys and not plasma: In mucopolysaccharidosis and pregnancy, levels are high in plasma but low or normal in urine: the relation between the activity levels of the various enzymes is similar in kidney and urine, but not in plasma. The activities of these enzymes were studied in various disorders, including a few inborn lysosomal diseases. A deficiency of β-galactosidase could be demonstrated in mucopolysaccharidosis types II and III, but not type IV. To detect this deficiency, the activity of N-acetyl-β-glucosaminidase was used as reference.