Usefulness of 4-methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-beta-D-glucopyrano sid e for the diagnosis of GM2 gangliosidoses in leukocytes.

4-Methylumbelliferyl-6-sulfo-2-acetamido-2-deoxy-beta-D-glucopyranoside was synthesized and tested as a substrate for the diagnosis of GM2 gangliosidoses using leukocytes. Less than 2% of normal activity was measured in homogenates from patients with typical Tay-Sachs disease and from a patient with a variant form having 37% Hexosaminidase A by heat denaturation using the usual fluorogenic substrate. An adult patient had 8.5% of normal activity. Three patients with Sandhoff disease were found to have values ranging from 17% to 37% of normal. These values overlap the range found for carriers of Tay-Sachs disease, and suggest that the usefulness of this substrate, while excellent for diagnosing B variants of GM2 gangliosidosis, requires further study. Perhaps when used together with 4-methylumbelliferyl-2-acetamido-2-deoxy-beta-D-glucopyranoside excellent discriminations of patients, carriers and controls will be realized.