THE HYDROLYSIS OF RAT THYROGLOBULIN BY THYROIDAL ENZYMES1

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Abstract
A saline extract containing thyroglobulin and a proteolytic enzyme was prepared from the thyroid glands of rats injected with radioiodide. The extent of hydrolysis of thyroglobulin after incubation of this extract was assessed by salting out, dialysis, chromatography and electrophoresis. As measured by salting out techniques, the hydrolysis of thyroglobulin occurred between pH 2.5 and 5.5, with peak activity at pH 4.9. 55% of the thyroglobulin was hydrolyzed at 48 hours, after which no further hydrolysis was observed. By paper chromatography, thyroxine, mono- and di-iodotyrosine and iodide were identified as products. Triiodo-thyronine was not detected. The salting out curve for rat thyroglobulin in phosphate buffer is similar to that described for other species.