<P> Thyroglobulin ( Tg ) is a 660 kDa , dimeric protein produced by the follicular cells of the thyroid and used entirely within the thyroid gland . Thyroxine is produced by attaching iodine atoms to the ring structures of this protein 's tyrosine residues ; thyroxine ( T ) contains four iodine atoms , while triiodothyronine ( T ) , otherwise identical to T , has one less iodine atom per molecule . The thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland . Each thyroglobulin molecule contains approximately 100 - 120 tyrosine residues , a small number of which ( < 20 ) are subject to iodination catalysed by thyroperoxidase . The same enzyme then catalyses `` coupling '' of one modified tyrosine with another , via a free radical - mediated reaction , and when these iodinated bicyclic molecules are released by hydrolysis of the protein , T3 and T4 are the result . hence , each Tg protein molecule ultimately yields very small amounts of thyroid hormone ( experimentally observed to be on the order of 5 - 6 molecules of either T4 or T3 per original molecule of Tg ) . </P>
<P> Thyroglobulin ( Tg ) is a 660 kDa , dimeric protein produced by the follicular cells of the thyroid and used entirely within the thyroid gland . Thyroxine is produced by attaching iodine atoms to the ring structures of this protein 's tyrosine residues ; thyroxine ( T ) contains four iodine atoms , while triiodothyronine ( T ) , otherwise identical to T , has one less iodine atom per molecule . The thyroglobulin protein accounts for approximately half of the protein content of the thyroid gland . Each thyroglobulin molecule contains approximately 100 - 120 tyrosine residues , a small number of which ( < 20 ) are subject to iodination catalysed by thyroperoxidase . The same enzyme then catalyses `` coupling '' of one modified tyrosine with another , via a free radical - mediated reaction , and when these iodinated bicyclic molecules are released by hydrolysis of the protein , T3 and T4 are the result . hence , each Tg protein molecule ultimately yields very small amounts of thyroid hormone ( experimentally observed to be on the order of 5 - 6 molecules of either T4 or T3 per original molecule of Tg ) . </P>
protein that serves as the precursor molecular for thyroid hormones
protein that serves as the precursor molecular for thyroid hormones
Thyroglobulin ( Tg )
Thyroglobulin ( Tg )