Use of N-acetyl-2'-O-methyllactosamine as a specific acceptor for the determination of alpha-L-(1----3)-fucosyltransferase in human serum.

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