N-Acetyllactosaminide Beta-1,6-N-Acetylglucosaminyl-Transferase (GCNT2) (IGnT)
During the development, poly-N-acetyllactosamine in human erythrocytes changes from linear form, N-acetyllactosamine repeats (i-antigen), to branched form (I-antigen). This conversion takes place due to an appearance of N-acetyllactosaminide β-1,6-N-acetylglucosaminyltransferase (I enzyme, also called I-branching enzyme, or GCNT2), transferring N-acetylglucosamine to galactose residue of poly-N-acetyllactosamine. The presence of I-enzyme was assumed based on a structural change, which was described in (Fukuda et al. 1979, Fig. 33.1). These carbohydrate structure i/I antigens and adult patients with antibodies reacting against i antigen were recognized. Antigen in those patients exhibited coagulation of blood cells when exposed to low temperature that caused cold hemolytic anemia. By using these antibodies, Chinese hamster ovary (CHO) cells that was transfected with polyoma large T antigen was used for expression cloning of I enzyme. Upon cloning of I-branching enzyme, the amino acid sequence of I-branching enzyme was found to be highly homologous to β-1,6-N-acetylglucosaminyltransferase (GCNT1) (C2GnT-1), which forms core2 branch of O-glycans. C2GnT-1 enzyme transfers N-acetylglucosamine to GalNAc residue of Galβ1-3GalNAc-Ser/Thr in β-1.6 linkage. These studies established that the carbohydrate structure similar to each other has similar enzyme protein structure; thus, the concept of the gene family in glycosyltransferases was established.
KeywordsChinese Hamster Ovary Carbohydrate Structure Congenital Cataract Expression Cloning Breast Tumor Sample
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