Use of N-acetyl-2′-O-methyllactosamine as a specific acceptor for the determination of α-l-(1→3)-fucosyltransferase in human serum

A synthetic substrate, N-acetyl-2′-O-methyllactosamine, was employed as a specific acceptor for α-l-(1→3)-fucosyltransferase from human serum. The fucosyl linkage of the product from this substrate was characterized by hydrolysis with a specific α-l-(1→3)/(1→4)-fucosidase. Using this acceptor, the pH optimum for the serum α-l-(1→3)-fucosyltransferase was 6.5. The enzyme was activated by Mn²⁺ or Mg²⁺ ions and was inhibited by EDTA. The apparent K_m for this enzyme using N-acetyl-2′-O-methyllactosamine was 20.4 mm and V_max was 5.6 pmol/h/ml serum.