Initiation of poly-N-acetyllactosamine chain biosynthesis occurs preferentially on complex multiantennary asparagine-linked oligosaccharides.

An N-acetyl-beta-D-glucosaminyltransferase activity involved in the initiation of poly-N-acetyllactosamine chain biosynthesis can be solubilized from Ehrlich ascites tumor cell microsomal membranes. The ability of this enzyme to act on linear and branched acceptor substrates has been studied. The results indicate that complex-type tri- and tetra-antennary oligosaccharides exhibiting the branching pattern beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----6)-[beta-D-Galp-(1----4)-beta- D- Glcp-NAc-(1----2)]-D-Man are the preferred substrates for the enzyme, and therefore, may represent the structures upon which the generation of poly-N-acetyllactosamine chains proceeds more efficiently.