Colominic acid (Polysialic acid) is a linear small polysaccharide containing α-2,8-linked sialic acid (neurominic acid) with (n = 8 to >100) residues.
Polysialic acid is an unusual post translational modification polysaccharide that is widely expressed in nature in bacterial capsules, fish, sea urchin eggs, embryonic tissues, amphibians, animal and human brains, and in a variety of cancers. The major carrier of polysialic acids in mammals is the neural cell adhesion molecule (a glycoprotein that belongs to the immunoglobulin superfamily).