Studies on the к-casein complex: II. The isolation of a sialic acid-containing fraction by disrupting the complex at low pH in the presence of sodium chloride

Abstract

When crude /c-casein was precipitated at pH 3 in the presence of 0*4 MNaCl the supernatant contained up to 80% of the total sialic acid but no detectable cystine or cysteine. Two fractions were obtained from this supernatant by chromatography on DEAE cellulose; one containing 4-6 % sialic acid and the other only onetenth of this amount.Most of the sialic acid of the sialic acid-rich fraction was soluble in 12 % trichloracetic acid following treatment with rennin. It is suggested that the glycopeptide released by the action of the enzyme on casein originates from this fraction.