Evidence that the aberrant alpha 1-->2fucosyltransferase found in colorectal carcinoma may be encoded by Fuc-TIII (Le) gene.

The accumulation of alpha 1-->2fucosylated antigens such as Le(b) and Y and the presence of aberrant alpha 1-->2 fucosyltransferase(s) (alpha 12FT) which showed new substrate specificities and must be involved in the accumulation of alpha 1-->2fucosylated antigens in colorectal carcinoma has been observed in our previous studies. In this study, we examined the substrate specificities of purified alpha 12FT from Colo201 cells and COS-1 cells transfected with the Fuc-TIII (Le) gene from a patient with colorectal carcinoma. It was demonstrated that activities of not only the Le gene related alpha 1-->3/4-fucosyltransferase but also the aberrant alpha 12FT were present in the purified preparation and in the extract of transfected COS-1 cells on which the Le(b) activity was expressed. These results suggested that the aberrant alpha 12FT was associated with the Le enzyme and that both enzymes could be encoded by the Fuc-TIII gene.