Tyrosine Metabolism via Thyroid Hormones and Other Halogenated Derivatives

Tyrosine Metabolism via Thyroid Hormones and Other Halogenated Derivatives 

In higher organisms a portion of the tyrosine is metabolized via the thyroid hormones. Physiologically these are highly active substances, and the amount of tyrosine metabolized by this pathway is probably relatively small. However, no quantitative figures appear to be available. 

The exact nature of the thyroid hormone, whether protein or otherwise, and the physiological and endocrinological aspects, such as the mutual interaction of thyroid and pituitary, cannot be discussed here. Excellent reviews are available elsewhere (e.g., 8, 31, 358, 673, 703, 751). 

Degradative studies suggested the presence of two benzene rings, a phenolic oxygen, an ether oxygen, and an alanine side chain. Of the possible structures, that now accepted for thyronine was considered most likely and was proved by synthesis (350). The position of the iodine 

The study of the thyroid hormones was greatly facilitated when radioactive isotopes of iodine became available. Using I it was soon con6rmed (576, 612, 665, 666) that activity administered as iodide was converted in the thyroid to diiodotyrosine and then thyroxine. 

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V. Tyrosine Metabolism via Thyroid Hormones and Other Halogenated Derivatives. 71... 

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