Purification of the N-acetylglucosaminide alpha(1-3/4)fucosyltransferase of human milk.

The N-acetylglucosaminide alpha(1-3/4)fucosyltransferase has been purified 1.8 x 10(6)-fold from human milk by ion-exchange chromatography, affinity chromatography on GDP-agarose and HPLC. The alpha(1-3/4)fucosyltransferase behaves in gel filtration-HPLC as a molecule of M(r) 98,000, and differs from the alpha(1-3)fucosyltransferase which behaves like a molecule of about M(r) 47,000. The enzyme is a glycoprotein, and the purified preparation appears in SDS polyacrylamide gel electrophoresis as a band of M(r) 44,000. The results present the first purification of human milk alpha(1-3/4)fucosyltransferase to apparent homogeneity, and suggest that the alpha(1-3/4)- and alpha(1-3)fucosyltransferase of human milk differ in their native molecular sizes, the former being a dimer of two subunits.