Recovery of Thyroxine from Thyroid Protein Hydrolyzed with Pancreatic and Bacterial Proteases

Two proteolytic enzyme preparations, one bacterial (Pronase) and the other pancreatic (Viokase), were compared for effectiveness in hydrolyzing thyroidal iodoprotein. The bacterial preparation is shown to be superior. It released iodotyrosines and thyroxine from thyroprotein more rapidly than did the pancreatic preparation. Pronase, however, was more active in deiodinating thyroxine. It is recommended that, for the accurate determination of the thyroxine in iodoproteins, periodic chromatographic analyses of thyroid digests be made to determine when maximal yields of thyroxine occur.