Ihara Y, Nishikawa A, Tohma T, Soejima H, Niikawa N, Taniguchi N
Department of Biochemistry, Osaka University Medical School.
J Biochem. 1993 Jun;113(6):692-8. doi: 10.1093/oxfordjournals.jbchem.a124105.
UDP-N-acetylglucosamine:beta-D-mannoside beta 1,4 N-acetylglucosaminyltransferase III (GnT-III) [EC 2.4.1.144] catalyzes the addition of N-acetylglucosamine in beta 1-4 linkage to the beta-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 COOH-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 22q.13.1 using fluorescence in situ hybridization.
UDP-N-乙酰葡糖胺：β-D-甘露糖苷β1,4 N-乙酰葡糖胺基转移酶III（GnT-III）[EC 2.4.1.144]催化以β1-4连接的方式将N-乙酰葡糖胺添加到N-连接糖链三甘露糖核心的β-连接甘露糖上，从而产生一个平分型GlcNAc残基。我们从胎儿肝脏cDNA文库中分离出了6个独立的人GnT-III cDNA克隆。该cDNA序列有一个开放阅读框，预测编码一个含531个氨基酸的蛋白质。与人GnT-III在核苷酸水平的同源性为86%，在氨基酸水平为91%。两种物种中氨基端跨膜结构域和催化结构域都高度保守。与人GnT-III相比，大鼠序列在“颈部”区域有四个氨基酸缺失，在COOH端区域也有一些差异。以其中一个人cDNA克隆为探针，从人黏粒文库中分离出了两个重叠的基因组克隆。利用荧光原位杂交技术，已将GnT-III基因定位到22q.13.1染色体上。
