Activity of UDP-GlcNAc: α-Mannoside β(1,6)N-acetylglucosaminyltransferase (GnT V) in cultured cells using a synthetic trisaccharide acceptor

N-acetylglucosaminyltransferase V activity has been measured under saturating conditions in the extracts of seven cultured cell lines using as substrates, UDP-[ 3H]-GlcNAc and a synthetic 8-methoxylcarbonyloctyl trisaccharide. The unreacted sugar-nucleotide and its breakdown products were separated from the radiolabeled tetrasaccharide product by reversephase chromatography. Enzyme activity was present in six of the cell lines, which were derived originally from either human, mouse, or hamster tissues, with the highest activity in mouse lymphoma BW5147 cells. The PHA R 2.1 variant cell line, derived from the BW5147 line, expressed no detectable activity.