Abstract
Tritiated human and porcine thyroglobulins were readily isolated after the enzymatic oxidation and reduction with galactose oxidase and catalase. Following gel chromatography only a single radioactive peak was eluted in the region which corresponds to the 19S protein. More tritium was incorporated into thyroglobulin (specific activity about 1.4 μCi/mg) after oxidation with galactose oxidase than in a control without the enzyme (specific activity about 0.21 μCi/mg).
No differences were detectable between the tritiated and the unlabelled protein using immunoelectrophoresis or immunodiffusion. These results indicate the presence of terminal galactose residues in purified thyroglobulin from two species and confirm that tritiation of the protein containing intact sialic acid residues can be effected.