Biochemical studies on an unusual case of fucosidosis

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Abstract
Biochemical studies have been performed on the spleen and liver of a patient suspected of having fucosidosis. The specific, complete deficiency of 4‐methylumbelliferyl (4‐MU)‐α‐L‐fucosidase activity coupled with the massive liver accumulation of polar glycolipids (comparable to those found in a known case of fucosidosis), confirms the diagnosis of fucosidosis. The patient is unusual in that his liver retains 25–50 % of normal α‐L‐fucosidase activity for the p‐nitrophenyl (PNP) substrate. The patient's spleen showed complete deficiency of α‐L‐fucosidase activity for both 4‐MU‐ and PNP‐α‐L‐fucopyranoside. The patient's crude liver α‐L‐fucosidase was not significantly different in thermostability when compared to the crude enzyme from a normal liver.After partial purification on agarose‐ɛ‐aminocaproyl‐fucosamine and sepharose‐concanavalin A, the patient's liver α‐L‐fucosidase was found to possess both PNP and 4‐MU activities. This suggests that components in the patient's crude liver supernatant may inhibit 4‐MU‐α‐L‐fucosidase activity. This was demonstrated further when the patient's liver supernatant was found to inhibit significantly normal liver 4‐MU‐α‐L‐fucosidase activity. Kinetic and immunochemical characterization indicated that the patient's α‐fucosidase was similar, if not identical, to the normal liver enzyme. Apparent Km's for 4‐MU‐α‐L‐fucopyranoside were determined to be 0.1 mM and 0.12 mM for the patient and normal liver enzyme, respectively. The IgG fraction of antiserum prepared against purified normal liver α‐L‐fucosidase immunoprecipitated 81 % of the patient's α‐L‐fucosidase, suggesting similarity of antigenic determinants.

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