Objective. The goal of this paper is to investigate the relationship between the N-glycosylation of acetylglucosaminyltransferase V（Glc NAcT-V） and its activity and to know which site among the 6 N-glycosylation sites in the GlcNAcT-V gene is the most important. Methods.Wild type of GlcNAcTV was transfected into COS7 cells and its activity was measured 48 h later. The first site （Asn 110） was mutated with sitedirected mutagenesis and transfected into COS7 cells. Results. It was found that after the cells were added tunicamycin（TM

1 μ g/ml）

the activity was 117% of the wild type. The activity of the cells with mutating GlcNAcTV was about 120% of the wild type RTPCR showed that there was no significant change in mRNA expression among the three groups. Conclusion.The Nglycosylation is important for its activity. Our results suggest that the Nlinked carbohydrates on GlcNAcTV are required for the posttranscriptional activity of the enzyme.