ENDOCYTOTIC INTERNALIZATION OF ALPHA-2-MACROGLOBULIN - ALPHA-GALACTOSIDASE CONJUGATE BY CULTURED FIBROBLASTS DERIVED FROM FABRY HEMIZYGOTE

Endocytotic internalization of .alpha.-galactosidase by cultured fibroblasts derived from a patient with Fabry''s disease was achieved via receptor-mediated endocytosis of .alpha.-2-macroglobulin (.alpha.-2-M). .alpha.-galactosidase of coffee beans was conjugated to .alpha.-2-M when the latter was treated with trypsin. Internalization of the conjugate resulted in an increase of .alpha.-galactosidase activity in the crude cell extracts. The observed internalization was blocked by the presence of bacitracin, an inhibitor of binding between .alpha.-2-M and its receptor on the cell surface. When the cells were incubated at 4.degree. C with the conjugate, internalization was also inhibited. The .alpha.-galactosidase activity in the cells was saturated when the concentration of the conjugate in the medium was 40 .mu.g/ml. Since non-conjugated .alpha.-galactosidase was not effectively internalized, the observed internalization of the conjugate was mediated by recognition of .alpha.-2-M by its receptor. The effective internalization of .alpha.-galactosidase described in this paper has a potential use in the enzyme replacement therapy of Fabry''s disease.