An electrophoretic variant of beta-galactosidase with altered catalytic properties in a patient with GM1 gangliosidosis.
In nine patients with GM1 gangliosidosis, liver ganglioside GM1 beta-galactosidase (EC 3.2.1.23) activity ranged from less than 0.01% to 0.05% of normal. In a tenth patient's liver, much higher activity was found (0.5% of normal). In this patient the residual enzyme had the same molecular weight as beta-galactosidase A, the major form of beta-galactosidase of normal human liver. No activity was found that corresponded to beta-galactosidase B, the minor form of human liver beta-galactosidase. On starch gel electrophoresis, the patient's enzyme migrated less anodally than normal beta-galactosidase A, both before and after treatment with neuraminidase. Beta-Galactosidase from the patient had a Km that was higher then normal; 5-fold higher with ganglioside GM1 and 2-fold higher with 4-methylumbelliferyl beta-galactoside. The patient's enzyme crossreacted immunologically with normal beta-galactosidase A and had about 100-fold more antigenic activity per unit catalytic activity than the normal enzyme. The results indicate that in this patient a beta-galactosidase A protein with altered charge and altered catalytic properties was present in relatively normal amounts, the first electrophoretic variant reported for a patient with a lysosomal hydrolase deficiency.
D001921:Brain / Q000201:enzymology; D002250:Carbon Radioisotopes; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D005696:Galactosidases / Q000172:deficiency / Q000302:isolation & purification / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000201:enzymology; D009154:Mutation; D013106:Sphingolipidoses / Q000201:enzymology* / Q000235:genetics
D002250:Carbon Radioisotopes; D005732:Gangliosides; D005696:Galactosidases; D006596:Hexosaminidases