Molecular cloning and characterization of β1,4‐N‐acetylgalactosaminyltransferases IV synthesizing N,N′‐diacetyllactosediamine1

[摘要]

A sequence highly homologous to β1,4-N-acetylgalactosaminyltransferase III (β4GalNAc-T3) was found in a database of human expressed sequence tags. The full-length open reading frame of the gene, β4GalNAc-T4 (GenBank accession number AB089939), was cloned using the 5′ rapid amplification of cDNA ends method. It encodes a typical type II transmembrane protein of 1039 amino acids having 42.6% identity with β4GalNAc-T3. The recombinant enzyme transferred N-acetylgalactosamine to N-acetylglucosamine-β-benzyl with a β1,4-linkage to form N,N′-diacetyllactosediamine as did β4GalNAc-T3. In specificity toward oligosaccharide acceptor substrates, it was quite similar to β4GalNAc-T3 in vitro, however, the tissue distributions of the two enzymes were quite different. These results indicated that the two enzymes have similar roles in different tissues.

[学科分类] 生物化学/生物物理

[关键词] Glycosyltransferase;N-Acetylgalactosaminyltransferase;N-Glycan;N;N′-Diacetyllactosediamine;Glycodelin;Lutropin;LacdiNAc;N;N′-diacetyllactosediamine (GalNAcβ1-4GlcNAc);GalNAc;N-acetylgalactosamine;GlcNAc;N-acetylglucosamine;LH;lutropin;Man;mannose;Gd;glycodelin;NeuAc;N-acetylneuraminic acid;Gal;galactose;Le;Lewis;Lex;Galβ1-4(Fucα1-3)GlcNAc;Fuc;fucose;Ley;Fucα1-2Galβ1-4(Fucα1-3)GlcNAc;β4GalNAc-T;β1;4-N-acetylgalactosaminyltransferase;β4GT;β1;4-glycosyltransferase;EST;expressed sequence tag;ORF;open reading frame;RACE;rapid amplification of cDNA ends;HEK;human embryonic kidney;GlcA;glucuronic acid;pNp;para-nitrophenyl;Bz;benzyl;Glc;glucose;Xyl;xylose;MS;mass spectrometry;MALDI-TOF;matrix-assisted laser desorption/ionization-time of flight;GAPDH;glyceraldehyde-3-phosphate dehydrogenase;HPLC;high performance liquid chromatography