β4GalT-II is a key regulator of glycosylation of the proteins involved in neuronal development

Seven members of the human β1,4-galactosyltransferase (β4GalTs) have been identified and characterized by many groups. β4GalTs play important roles in the extension of N- and O-linked glycans involved in several biological events. However, it has not been clear which β4GalTs can act on glycoproteins, such as α-dystroglycan and Notch receptors, involved in neuronal development. To clarify which β4GalTs can function, we determined the enzyme activities toward such motifs and the transcript levels in human normal tissues. Among human β4GalTs, both β4GalT-I and β4GalT-II could act efficiently on all substrates, but the relative activity of β4GalT-II was higher than that of β4GalT-I. Transcript of β4GalT-I was widely expressed except for brain, and on the other hand, that of β4GalT-II was expressed at high levels in the brain. Thus, these results suggest that among human β4GalTs, β4GalT-II is a major regulator of the synthesis of glycans involved in neuronal development.