Involvement of beta-1,4-galactosyltransferase V in malignant transformation-associated changes in glycosylation

In spite of marked changes in the glycosylation upon malignant transformation of cells, no biological significance of beta-1, 4-galactosyltransferase (beta-1,4-GalT) activities has been elucidated. When beta-1,4-GalT activities toward 1 mM GlcNAcbeta-S-pNP were determined using homogenates of NIH3T3 and its transformant, MTAg, MTAg contained 1.3 times higher activities. Northern blot analysis, however, revealed that the beta-1,4-GalT V gene expression increases by three times with a decrease in that of beta-1,4-GalT II by one-fifth and without significant changes in those of other beta-1,4-GalTs in MTAg. Analysis of beta-1,4-GalT V acceptor-specificity showed that the GlcNAcbeta1-->6Man group of the GlcNAcbeta1-->6(GlcNAbeta1-->2)Manalpha1- branch is galactosylated. These results indicate that changes in beta-1,4-GalT II and V activities are important for the altered glycosylation.