期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：2
页码：406-411
DOI：10.1073/pnas.96.2.406
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Human and mouse cDNAs encoding a new {beta}-1,3-N-acetylglucosaminyltransferase ({beta}3GnT) have been isolated from fetal and newborn brain libraries. The human and mouse cDNAs included ORFs coding for predicted type II transmembrane polypeptides of 329 and 325 aa, respectively. The human and mouse {beta}3GnT homologues shared 90% similarity. The {beta}3GnT gene was widely expressed in human and mouse tissues, although differences in the transcript levels were visible, thus indicating possible tissue-specific regulation mechanisms. The {beta}3GnT enzyme showed a marked preference for Gal({beta}1-4)Glc(NAc)-based acceptors, whereas no activity was detected on type 1 Gal({beta}1-3)GlcNAc and O-glycan core 1 Gal({beta}1-3)GalNAc acceptors. The new {beta}3GnT enzyme was capable of both initiating and elongating poly-N-acetyllactosamine chains, which demonstrated its identity with the poly-N-acetyllactosamine synthase enzyme (E.C. 2.4.1.149 ), showed no similarity with the i antigen {beta}3GnT enzyme described recently, and, strikingly, included several amino acid motifs in its protein that have been recently identified in {beta}-1,3-galactosyltransferase enzymes. The comparison between the new UDP-GlcNAc:{beta}Gal {beta}3GnT and the three UDP-Gal:{beta}GlcNAc {beta}-1,3-galactosyltransferases-I, -II, and -III reveals glycosyltransferases that share conserved sequence motifs though exhibiting inverted donor and acceptor specificities. This suggests that the conserved amino acid motifs likely represent residues required for the catalysis of the glycosidic ({beta}1-3) linkage.
