[beta-galactosidosis--GM1 gangliosidosis and Morquio B disease].

beta-galactosidosis is a lysosomal storage disorder caused by a deficiency of acid beta-galactosidase, including to autosomal recessive diseases; GM1-gangliosidosis (neurovisceral form) and Morquio B disease (skeletal form). To date, 26 different mutations in the beta-galactosidase gene have been identified in patients with beta-galactosidosis from various ethnic groups. Transient expression of the mutant genes has confirmed that mutant enzymes responsible for infantile GM1-gangliosidosis have almost no detectable beta-galactosidase activity. But the other three forms (late infantile/juvenile, adult/chronic GM1-gangliosidosis and Morquio B disease) are characterized by specific mutant enzymes with significant residual enzyme activity. Heterogeneous patterns of post-translational processing and maturation in these mutant enzymes are closely related to the phenotypic variations in beta-galactosidosis.