Corneal alpha-galactosidase deficiency in macular corneal dystrophy

Glycosidases, which cleave sugar molecules from complex glycopolymers, have been previously quantified in normal human cornea in our laboratory. Data quantifying glycosidases in macular corneal dystrophy are lacking. Tissue obtained at keratoplasty from patients with macular dystrophy and normal corneas obtained from eye bank eyes were used to determine levels of glycosidase activity. A fluorometric technique was employed using 4-methyl-umbelliferyl-glycosides as substrates. The corneal tissues were homogenized, centrifuged, and the supernatants assayed for enzyme activity. Specific activities (μml mol/ mg protein/hour) were determined and Km and Vmax values were obtained for all but one enzyme. Activity of alphagalactosidase was significantly lower in cornea tissue and keratocytes from macular corneal dystrophy compared to normal.