Role of sialic acid on the viscosity of canine tracheal mucin glycoprotein.

The role of sialic acid on the viscosity of canine tracheal mucin (CTM) was investigated. The mucin glycoprotein, purified from canine tracheal mucus, was subjected to mild acid hydrolysis with aqueous acetic acid and autohydrolysis in water, in which approximately 50% drop in the relative viscosity (nr) occurred. Carbohydrate compositional analysis before and after mild acid hydrolysis and autohydrolysis showed the complete removal of glycosidically bound sialic acid residues while all other sugar residues (i.e. galactose, N-acetyl galactosamine and N-acetyl glucosamine) remained unaltered, indicating that sialic acid residues are contributing towards the viscosity of CTM to a greater extent.