Studies in immunochemistry. 20. The action of papain and ficin on blood-group-specific substances

Abstract

The digestion of the blood-group-specific mucopolysaccharides with activated crystalline papain or ficin at pH 4-0 or 7-6 brings about a rapid fall in viscosity and a considerable, but limited, loss in the capacity of the materials to inhibit specific hemagglutination. The rate and extent of hydrolysis depend on the concentration of the enzyme and on the pH. The influence of the presence of activators and an inhibitor, p-chloromercuribenzoate, is considered. Trypsin, chymotrypsin, plasmin, pepsin and a mould protease appear to have no action on the group-specific mucopolysaccharides. The results suggest that there are a limited number of peptide bonds broken. The minimum number is probably about 4 in the initial phase of the reaction for a mucopolysaccharide of about 2-50X105 molecular weight. The changes in viscosity and serological activity and the liberation of titratable groups occur simultaneously and early in the hydrolysis and take place irrespective of the serological specificity of the mucopolysaccharide. These findings suggest that the kind of linkages broken are common to all the group-specific substances tested and therefore involve structures not primarily responsible for serological specificity.