Leukocyte β-Galactosidase Activity in GM1-Gangliosidosis

Abstract

The recent article by Singer et al. entitled "Leukocyte beta-Galactosidase Activity in the Diagnosis of Generalized GM1-Gangliosidosis," prompts us to report the results of two years of routine service assay of this enzyme in leukocytes using the alternative substrate, 4-methyl-umbelliferyl β-D-galactopyranoside. The β-galactosidase assay medium contained McIlvaine phosphate-citric acid buffer, pH, 4.1 (40µl); 4-methylumbelliferyl β-D-galactopyranoside (1 mM in buffer, 150µl) and leukocyte extract in 0.2 MKCl (10µl). After incubation for 15 minutes at 30°C, the reaction was stopped by the addition of 0.25 M glycine-NaOH, pH, 10.4 (1 ml) and the fluorescence measured.