MOLECULAR-FORM AND SUBCELLULAR-DISTRIBUTION OF ACID BETA-GALACTOSIDASE IN FIBROBLASTS FROM PATIENTS WITH G(M1) GANGLIOSIDOSIS, MORQUIO-B-DISEASE AND GALACTOSIALIDOSIS

The molecular form and subcellular distribution of acid beta-galactosi dase in cultured fibroblasts from patients with beta-galactosidase def iciency (G(M1)-gangliosidosis, Morquio B disease and galactosialidosis ) were studied, using antibodies against three different forms of the human enzyme: a high-molecular-weight multienzymic complex, a recombin ant 84-kDa precursor, and a 61--kDa tryptic product of the precursor. The mature enzyme from normal fibroblasts was immunoprecipitated by th e anti-complex and anti-64-kDa protein antibodies, but not by the anti -84-kDa precursor one, Immunofluorescence staining of normal fibroblas ts revealed the granular (lysosomal) distribution with anti-64-kDa pro tein antibody and the perinuclear reticular distribution with anti-84- kDa precursor antibody, probably representing the Golgi apparatus. Bot h patterns were demonstrated in Morquio B disease, but the residual en zyme activity was exclusively due to the mature enzyme, In Type 1 gala ctosialidosis, most of the expressed enzyme was detected as the precur sor form with a perinuclear reticular distribution. In Type 2 galactos ialidosis, more than half of the enzyme activity was due to the mature form with a lysosomal distribution. Fibroblasts from a patient with C -M1 gangliosidosis, expressing no beta-galactosidase mRNA, did not rea ct against either anti-64-kDa protein antibody or anti-84-kDa precurso r antibody. The combined use of Immunoprecipitation and immunostaining was useful for analysing the pathophysiology of the intracellular pro cessing and transport of the mutant beta-galactosidase. (C) 1997 Elsev ier Science B.V.