[14C-1-Tyrosine metabolism on rat thyroid gland]

Amino acid composition of incubation medium, thyroid tissue hydrolysate and purified thyreoglobulin (Tr) preparations, isolated after 5 hour incubation with 14C-1-tyrosine in Jey medium is studied by means of electrophoresis and autoradiography. 5 radioactivity stains are detected on radioelectrophoregram of incubation medium, 2 of them corresponding to tyrosine and serine. 2 stains corresponding to diiodotyrosine and triiodotyronine are found in hydrolysate of thyroid tissue. No radioactive stains were found on radioelectrophoregrams of thyreoglobulin. The data obtained indicate that in the reaction of condensation of iodotyrosines into iodotyronine a lateral chain of iodotyrosine (serine) splits off. Thyroid hormones biosyntesis takes place by condensation of either a single free molecule of iodotyrosine with iodotyrosyl residue of polypeptide chain of pre-synthesized thyreoglobulin, or two free molecules of iodotyrosine.