the mixtures were subjected to alkaline proteinase and trypsinase digestion at 50 C for 24 h, added with the same volume of 0.2 M sodium phosphate buffer (pH 7.4), containing 6.4 mg papain in the presence of 18 mg EDTA and 8 mg cysteine, and incubated at 50 C for 24 h. The reaction was ended by heating the mixtures at 100 C for 5 min.