Determination of the HNK-1 epitope (3-sulphated glucuronic acid) in intact chondroitin sulphates by ELISA. Application to squid skin proteoglycans and their oversulphated carbohydrate structures

The reactivity of the HNK-1 monoclonal antibody to chondroitin sulphates and derived disaccharides was studied using an ELISA inhibition test. The antibody readily reacted with its specific epitope (3-sulphated glucuronic acid) in intact chondroitin sulphates as well as with the equivalent oversulphated Δ 4-disaccharides obtained by chondroitinase digestion and identified as sulphated at C-3 of the hexuronate. It is showed that by using the oversulphated Δ 4-disaccharides as standards in an ELISA inhibition test, the amount of 3-sulphated glucuronic acid can be estimated also in the polymer preparations. When applying this ELISA test to the PG populations isolated from squid skin, most of the oversulphation seen in HPLC analyses of these preparations was found to be associated with 3-sulphation of the glucuronic acid.