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The acceptor substrate specificity of human β4‐galactosyltransferase V indicates its potential function in O ‐glycosylation
Author(s) -
van Die Irma,
van Tetering Angelique,
Schiphorst Wietske E.C.M,
Sato Takeshi,
Furukawa Kiyoshi,
van den Eijnden Dirk H
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00462-7
Subject(s) - recombinant dna , glycosylation , acceptor , galactosyltransferase , glycoprotein , glycan , biochemistry , enzyme , substrate (aquarium) , chemistry , in vitro , function (biology) , microbiology and biotechnology , stereochemistry , biology , gene , genetics , ecology , physics , condensed matter physics
In order to assess the function of the different human UDP‐Gal:GlcNAc β4‐galactosyltransferases, the cDNAs of two of them, β4‐GalT I and β4‐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 β4‐GalT V was more than 15 times lower than that of β4‐GalT I, using GlcNAcβ‐S‐ p NP as an acceptor. Whereas β4‐GalT I efficiently acts on all substrates having a terminal β‐linked GlcNAc, β4‐GalT V appeared to be far more restricted in acceptor usage. β4‐GalT V acts with high preference on acceptors that contain the GlcNAcβ1→6GalNAc structural element, as found in O ‐linked core 2‐, 4‐ and 6‐based glycans, but not on substrates related to N ‐linked or blood group I‐active oligosaccharides. These results suggest that β4‐GalT V may function in the synthesis of lacNAc units on O ‐linked chains, particularly in tissues which do not express β4‐GalT I, such as brain.