Embryonic and adult forms of two galactosyltransferases differ in their degrees of sialylation.

Embryonic and adult chicken liver galactosyltransferases behave differently on DEAE-Sepharose chromatography. After solubilization, two embryonic activities (one transfers galactose in a β1&-4 linkage to asialo-agalacto-α₁-acid glycoprotein and to N-acetylglucosamine; the other transfers galactose in a β-3 linkage to asialo-ovine submaxillary mucin) elute after the bulk of the protein, and after free glucose. The same two enzymes in adults elute more rapidly, almost coincident with the bulk of the protein, and before free glucose. The difference in elution patterns occurs when the column buffer contains 0.1 M NaCl. Without salt, both embryonic and adult transferases bind to the column, but with 0.5 M NaCl, the embryonic and adult transferases elute identically, and with the bulk of the protein. After treatment with neuraminidase, the embryonic transferase activities elute significantly earlier on a DEAE-Sepharose column in the presence of 0.1 M NaCl. The embryonic forms migrate more rapidly than do the adult forms on cellulose acetate electrophoresis, but neuraminidase treatment renders both enzyme forms immobile in this system. Neuraminidase treatment also inhibits the binding of the embryonic transferases to a wheat-germ-agglutinin-Sepharose column. Kinetically, the embryonic and adult transferases are indistinguishable. [ABSTRACT FROM AUTHOR]