The properties of thyroglobulin. XV. The function of the protein in the control of diiodotyrosine synthesis.

Thyroglobulin has been iodinated at pH 9.35 and the distribution of iodoamino acids has been determined. Iodination results in a decrease in the tyrcsyl and an increase in the diiodotyrosyl difference spectra peaks. The spectral changes indicate that tyrosyl groups, which are more or less shielded from the solvent, can also react with iodine. Based on recent model studies on the rates of iodination of Nacetyltyrosine and N-acetyliodotyrosine, it is suggested that the environment of the tyrosyl groups determines the relative amounts of monoiodotyrosine and diiodotyrosine that are synthesized. A functional role of the native form of the protein is thus envisioned in the control of the products formed by iodination.