Mannosidosis: separation and characterization of two acid alpha-mannosidase forms in mutant fibroblasts.

Two acidic forms of alpha-mannosidase activity, A and B, are separated and characterized in fibroblasts from controls and patients with mannosidosis. In normal cells, A and B differ in adsorption on DEAE-cellulose, electrophoretic mobility, stability at 70 degrees C and resistance to freezing at --20 degrees C. In 5 of 6 mutant cell lines, A and B both exhibit altered Km's for artificial substrates and decreased thermal stability. Zn2+ has no effect on A or B in mutant or normal cells. In contrast, Co2+ slightly inhibits B in normal cells but markedly enhances the activity of B in mutant cells. The mutation in mannosidosis clearly results in an alteration in the biochemical characteristics of both major acidic forms of alpha-mannosidase.