1993 Volume 113 Issue 6 Pages 692-698
UDP-N-acetylglucosamine: β-D-mannoside β1, 4 N-acetylglucosaminyltransferase III (GnT-III) [EC 2. 4. 1. 144] catalyzes the addition of N-acetylglucosamine in β1-4 linkage to the β-linked mannose of the trimannosyl core of N-linked sugar chains to produce a bisecting GlcNAc residue. We have isolated six independent cDNA clones of human GnT-III from a fetal liver cDNA library. The cDNA sequence has an open reading frame that predicts a protein of 531 amino acids. The homology to rat GnT-III is 86% at the nucleotide level and is 91% at the amino acid level. The amino-terminal transmembrane domain and the catalytic domain are well conserved in the two species. Human GnT-III has a deletion of four amino acids in the “neck” region and several differences in the COON-terminal region compared with the rat sequence. Using one of the human cDNA clones as the probe, two overlapping genomic clones have been isolated from a human cosmid library. The GnT-III gene has been mapped to chromosome 22 q. 13. 1 using fluorescence in situ hybridization.
