From Big Medical Encyclopedia

IODTYROSINES — the components of specific protein of a thyroid gland of thyreoglobulin participating in synthesis of its hormones; the iodated derivative amino acids of tyrosine. K Y. belong: monoiodtyrosine and diiodotyrosine:

Diiodotyrosine (DIT) is discovered in 1896 by E. Drechsel as a product of alkaline hydrolysis of a horn skeleton of corals of Gorgonia cavolinii and called yodgorgonovy to - that. Monoiodtyrosine (MEATH) K. Fink is open (To. Fink) and R. R. Fink in 1948 in hydrolyzates of a thyroid gland.

Y. are formed in follicular cells (according to other data, in a cavity of follicles) a thyroid gland in the course of iodination of molecules of thyreoglobulin at biosynthesis of this glycoprotein. Reaction happens under the influence of enzyme of the peroxidase oxidizing with the participation of hydrogen peroxide the iodide absorbed by a thyroid gland in elementary iodine which reacts with tyrosine in a molecule of thyreoglobulin with formation of monoiodtyrosine; at additional iodination of monoiodtyrosine there is a diiodotyrosine:

H 2 O 2 + 2I - +> 2H - 2H 2 O + I 2

I 2 + tyrosine -> MEATH + I - + H +

MEATH + I 2 -> DIT + I - + H +

Y. in a thyroid gland are in the connected state, in structure thyreoglobulin (see), are also released at euzymatic hydrolysis of thyreoglobulin in follicles of gland. Condensation Y. leads to formation of thyroid hormones thyroxine (see) and triiodothyronine (see). Thyroxine and triiodothyronine cosecrete in blood, and free Y. are deiodinated with the participation of enzymes of a deiodinase and, as a rule, do not come to the circulating blood. The iodide which is released during the deiodinating of iodtyrosines is used in processes of biosynthesis of thyroid hormones again. In the thyreoglobulin emitted from a thyroid gland, a ratio MEATH: DIT depends on amount of iodine. At the person in the molecule of thyreoglobulin containing 0,3 — 0,5% of iodine, number of the remains MEATH equally 6 — 7, the remains of DIT — 3 — 4. At increase in extent of iodination up to 1,0 — 1,2% the number of the remains increases, and the number of the remains of DIT can equal or exceed number of the remains MEATH. In the thyreoglobulin with the low content of iodine emitted from a nodal craw, the number of the remains is reduced also a ratio MEATH: DIT is more sharply shifted to the right. Biol, role And. it is limited to participation in biosynthesis yodtironin (see), hormonal activity Y. do not possess.

In a free look Y. are found in insignificant quantities in a thyroid gland. Emergence in blood Y. it is observed at thyrotoxicosis (see), thyroiditis (see), at destruction of a thyroid gland a radioiodine and surgical interventions on it.

Drugs Y. Betazinum (see) and diiodotyrosine are used at treatment of diseases of a thyroid gland. Diiodotyrosine possesses thyreostatic action, is more effective at a thyrotoxicosis of easy and average degree; a dose of drug 0,1 — 0,15 g a day.

Bibliography Thyroid hormones, under the editorship of. I. X. Turakulova, Tashkent, 1972.

I. X. Turakulov.