Fucosidosis: Deficiency of Alpha-l-fucosidase in Cultured Skin Fibroblasts

Fucosidosis is a newly recognized inborn error of metabolism involving the accumulation o f fucolipids, fucoglycoproteins, a n d fucornucopolysaccharides. T h r e e families h a v e been reported in the literature (1, 2). 1 T h e enzymic defect in fucosidosis has been established b y Van Hoof and Hers (3) as a specific, nearly complete deficiency of the enzyme ~-L-fucosidase. Thusfar, no reports h a v e appeared in which ~-fucosidase has been shown to be deficient in cultured skin fibroblasts from affected patients, nor have normal values been given for the activity of the enzyme in amniotic cells. I n this s t u d y we demonstrate deficiency of a-fucosidase in cultured skin fibroblasts from two brothers with fucosidosis and give normal values for the a c t i v i t y of c~-fucosi-dase in amniotic cells. The clinical picture of the patients from whom skin biopsies were taken will be reported in detail elsewhere. We are indebted to Dr. George Donnell who sent fibroblasts to us. The initial diagnosis of fucosidosis in both brothers was made using the serum assay of c~-fucosidase which we reported (4). Fibroblasts were cultured as described previously (5-7). They were harvested for enzyme assay at 14 days after subculture by mechanical scraping from flasks and centrifuging the cells into a pellet. Alpha-L-fucosidase activity was determined as follows. The cell pellet was weighed, diluted in 5 volumes of distilled water, and homogenized in a ground glass homogenizer. 20 gl of homogenate were taken and to this was added 50 /zl of p-nitrophenyl O~-L-fucopyranoside (1.5 m~, pierce Chemical Co., Rockford, Ill., in citrate-phosphate buffer, 0.1 M with respect to phosphate, pH 5.8), and the sample was incubated at 37°C for 2 and 4 hr. The reaction was stopped by adding 100 #1 of 3% trichloroacetic acid. Samples were then centrifuged at 3000 g for 10 rain, the supernatant was aspirated, taking care not to disturb the sediment, and 350 #1 of glycine-carbonate buffer (0.25 M, pH 10) was added to the supernate. Optical density was then read at 420 m# on a spectrophotometer and p-nitrophenyl was quantified using a standard curve. Tissue blanks for each sample were prepared in the same manner, substituting distilled