alpha-l-Fucosidase was partially purified from the liver of a
fucosidosis patient by column chromatography either on
agarose-epsilon-aminohexanoylfucosamine or on
concanavalin A-Sepharose, despite no apparent enzymic activity in the crude liver supernatant. Mixing studies indicated that the liver of the
fucosidosis patient did not lack activators or contain inhibitors of
alpha-l-fucosidase activity. The partially purified
alpha-l-fucosidase from the liver of the
fucosidosis patient exhibits a 4-5-fold-increased Michaelis constant for the 4-methylumbelliferyl substrate (700-750mum) and a greatly decreased thermostability at 55 degrees C compared with the normal liver
enzyme. The pH-activity curve is similar to that for the normal
enzyme between pH5 and 8, but quite dissimilar in the
acid region (pH3.0-4.5): below pH4.5 the
alpha-l-fucosidase shows no activity, whereas the normal
enzyme retains considerable activity (>/=50% of maximal activity). Isoelectric focusing of the
alpha-l-fucosidase revealed one major form with pI5.8 and other possible minor forms. No cross-reacting material was detected when the
alpha-l-fucosidase was run in double-immunodiffusion experiments against the
immunoglobulin-G fraction of anti-(
alpha-l-fucosidase)
antibodies, but the
enzyme was immunoprecipitated by this
immunoglobulin-G fraction. For at least the
fucosidosis patient being studied here, all the data suggest retention of a thermolabile portion of normal
alpha-l-fucosidase (with characteristic Michaelis constant and pH-activity curve) or production of a kinetically altered
alpha-l-fucosidase with decreased catalytic activity but antigenic similarity to the normal
enzyme.