The acceptor substrate specificity of human beta4-galactosyltransferase V indicates its potential function in O-glycosylation

FEBS Lett. 1999 Apr 30;450(1-2):52-6. doi: 10.1016/s0014-5793(99)00462-7.


In order to assess the function of the different human UDP-Gal:GlcNAc beta4-galactosyltransferases, the cDNAs of two of them, beta4-GalT I and beta4-GalT V, were expressed in the baculovirus/insect cell expression system. The soluble recombinant enzymes produced were purified from the medium and used to determine their in vitro substrate specificities. The specific activity of the recombinant beta4-GalT V was more than 15 times lower than that of beta4-GalT I, using GlcNAc beta-S-pNP as an acceptor. Whereas beta4-GalT I efficiently acts on all substrates having a terminal beta-linked GlcNAc, beta4-GalT V appeared to be far more restricted in acceptor usage. Beta4-GalT V acts with high preference on acceptors that contain the GlcNAc beta1-->6GalNAc structural element, as found in O-linked core 2-, 4- and 6-based glycans, but not on substrates related to V-linked or blood group I-active oligosaccharides. These results suggest that beta4-GalT V may function in the synthesis of lacNAc units on O-linked chains, particularly in tissues which do not express beta4-GalT I, such as brain.

Publication types

  • Comparative Study

MeSH terms

  • Baculoviridae / genetics
  • Blotting, Western
  • Carbohydrate Conformation
  • Carbohydrate Sequence
  • DNA, Complementary / metabolism
  • Galactosyltransferases / genetics
  • Galactosyltransferases / metabolism*
  • Glycosylation
  • Humans
  • Kinetics
  • Lactalbumin / metabolism
  • Molecular Sequence Data
  • Recombinant Proteins / metabolism
  • Substrate Specificity


  • DNA, Complementary
  • Recombinant Proteins
  • Lactalbumin
  • Galactosyltransferases