Characterization of UDP-N-acetylglucosamine:alpha-6-d-mannoside beta-1,6-N-acetylglucosaminyltransferase V from a human hepatoma cell line Hep3B.
UDP-N-acetylglucosamine:alpha-6-d-mannoside beta-1, 6-N-acetylglucosaminyltransferase V (GlcNAcT-V) has been purified from cell extracts of the human hepatoma cell line, Hep3B, with 8.7% recovery. The purified enzymes had molecular masses of about 67 and 65 kDa on denaturated and natural conditions, respectively. The values of pI was 5.9. The GlcNAcT-V, when resolved by SDS-PAGE, was positive for Schiff staining, suggesting that the enzyme is glycoprotein. When GlcN,GlcN-biant-PA and UDP-GlcNAc were used as substrates, the enzyme displayed a temperature optimum of around 50 degrees C and optimum an pH of 6.5. The enzyme was stable in response to incubation from pH 4.5 to pH 10.5 at 4 degrees C for 24 h. The presence of UDP-GlcNAc and GlcN,GlcN-bi-PA protected the enzyme from heat inactivation, the extent depending upon the substrate concentration. The activity of the enzyme was stimulated by Mn2+ ion; however, it was inhibited by Fe3+. The enzyme activity was inhibited by another series of NDP-sugars including ADP-, CDP-, GDP-, and TDP-GlcNAc. Studies on the activity of the enzyme toward a variety of pyridylaminated sugars showed that the enzyme is most active toward biantennary (GlcN,GlcN-bi-PA) sugars. The enzymes had apparent Km values of 1.28 and 5.8 mM for GlcN,GlcN-bi-PA and UDP-GlcNAc, respectively. In order to isolate the GlcNAcT-V gene, PCR primers of GNN-1 and GNN-8 were designed and the amplified PCR product carrying the gene was cloned and sequenced. Nucleotide sequence analysis showed a 2220-bp open reading frame encoding a 740-amino-acid protein. This was almost same as the previously reported human sequences, except for some sequence differences in three amino acids. The three amino acid changes were as follows: 375V --> L, 555T --> R, and 592A --> G. These studies represent the detailed characterization of a purified GlcNAcT-V from human hepatoma cell Hep3B.
Park
C
C
College of Oriental Medicine, Dongguk University, Sukjang-Dong 707, Kyungju City, Kyungpook, 780-714, Korea.
Jin
U H
UH
Lee
Y C
YC
Cho
T J
TJ
Kim
C H
CH
D001483:Base Sequence; D002240:Carbohydrate Sequence; D006528:Carcinoma, Hepatocellular / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D017351:N-Acetylglucosaminyltransferases / Q000737:chemistry* / Q000302:isolation & purification; D013696:Temperature; D014407:Tumor Cells, Cultured
D007477:Ions; D017351:N-Acetylglucosaminyltransferases; C052254:alpha-1,6-mannosylglycoprotein beta 1,6-N-acetylglucosaminyltransferase