Release and Breakdown of Sialic Acid from Human Salivary Mucin and its Role in the Formation of Dental Plaque

Abstract

SIALIC acid is a constituent of human salivary mucin obtained by precipitating the mucin from saliva with either ammonium sulphate, weak acids, acetone or alcohol. Dried salivary mucin contains 2 per cent sialic acid¹. In man, so far, the only sialic acid to be found from over a dozen different sources² has been N-acetylneuraminic acid (NANA), and it is reasonable to assume that it exists in this form also in human salivary mucin. Sialic acid, estimated as NANA by Svennerholm's method³, is found in freshly collected, human, wax-stimulated saliva. There was a wide variation between different individuals and between the same individuals on different occasions. The mean of 40 determinations gave a value of 45 µg/ml. with a standard deviation of 12 µg/ml. and a range of 19–85 µg/ml. Dental plaque, however, which is believed to contain mucin⁴, contained zero or trace amounts of NANA in over 40 determinations. The sialic acid must be lost from the mucin either when present in the saliva or else very rapidly during formation of the dental plaque.