N-acetylglucosaminyltransferase (GnT) assays using fluorescent oligosaccharide acceptor substrates: GnT-III, IV, V, and IX (GnT-Vb).

Determining glycosyltransferase activities gives a clue for better understanding an underlying mechanism for glycomic alterations of carrier molecules. N-glycan branch formation is concertedly regulated by cooperative and competitive activities of N-acetylglucosaminyltransferases (GnTs). Here, we describe methods for large scale preparation of the oligosaccharide acceptor substrate, fluorescence-labeling of oligosaccharides by pyridylamination, quality control, and reversed phase HPLC-based measurement of GnT activities including GnT-III, IV, V, and IX.