 The resulting product, GDP-L-colitose, is then incorporated into the O-antigen by glycosyltransferases and "O"-antigen processing proteins.Further reactions join the O-antigen to the core polysaccharide to form the full lipopolysaccharide.ColD is a PLP-dependent enzyme responsible for the removal of the C-3' hydroxyl group during the biosynthesis of GDP-colitose.