Human serum α-l-fucosidase

Human serum α-l-fucosidase has been purified 241 200-fold with 35% yield by an affinity Chromatographie procedure utilizing agarose-ε{lunate}-aminocaproyl-fucosamine. Isoelectric focusing of the purified enzyme indicated the presence of several forms, with the form at pI 5.0 comprising the majority of the activity. Assay of the purified α-l-fucosidase showed only trace amounts of contaminating glycosidases present, with β-galactosidase being the largest contamnant (0.5% by activity). Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated the presence of two subunits with very similar molecular weights (56500 and 54000). Using the p-nitrophenyl substrate, the purified serum α-l-fucosidase had an apparent Michaelis constant of 0.52 mM and a broad pH optimum centered around pH 4.8 with a second, minor optimum at pH 6.1. Gel filtration on Sepharose 6-B indicated an apparent molecular weight of 296 000 ± 30 000. Preincubation with antibodies made previously against purified liver α-l-fucosidase led to quantitative immuno precipitation of the purified serum α-l-fucosidase. Assay of the purified serum α-l-fucosidase for sialic acid indicated the presence of 1.7 μg sialic acid per 100 μg enzyme, about twice that previously found for the purified liver enzyme.