Thyronine

Only the small amounts of T and T that are free in the circulation can be metabolized. The main route is deiodination of T to T and i-T, and from these to other inactive thyronines (21). Most of the Hberated iodide is reabsorbed in the kidney. Another route is the formation of glucuronide and sulfate conjugates at the 4 -OH in the Hver. These are then secreted in the bile and excreted in the feces as free phenols after hydrolysis in the lower gut. 

In a procedure known as the iodonium condensation, substituted diaryhodonium compounds react with tyrosines. Thyronines with substituents other than NO2 or I at the 3 and 5 positions are obtained. 

Synthesis L-diiodo thyronine (1.05 g) is dissolved in ammonia (specific gravity 0.880)... 

Purification The crude precipitate is dissolved in boiling 2N HCl (300 ml) and filtered from the relatively insoluble thyroxine hydrochloride. The hot filtrate is brought to pH 4 with 5N NaOH and triiodo thyronine again separates after chilling at 0° to 4°C it is collected, washed with water and dried. The yield of triiodo thyronine is 70 to 75% of the theoretical. This triiodo thyronine still contains some thyroxine (about 10%). 

The final purification consists of chromatographic separation of thyroxine and triiodo thyronine on a kieselguhr column using 20% chloroform in n-butanol equilibrated with... 

N NaOH as the developing solvent. 80 to 100 mg triiodo thyronine is purified during... 

Pyridinol carbamate 160 ,170 -Dihyd roxy progesterone Algestone acetophenide L-Diiodo thyronine Liothyronine p-Diisobutylphenol... 

The thyroid hormones T3 and T4 are unique in that iodine (as iodide) is an essential component of both. In most parts of the world, iodine is a scarce component of soil, and for that reason there is htde in food. A complex mechanism has evolved to acquire and retain this cmcial element and to convert it into a form suitable for incorporation into organic compounds. At the same time, the thyroid must synthesize thyronine from tyrosine, and this synthesis takes place in thyroglobuhn (Figure 42-11). 

PNP-DTP has been used to photoaffinity label the thyroid hormone nuclear receptors in intact cells by preparing a derivative of 3,5,3 -triiodo-L-thyronine with the crosslinker (Pascual et al., 1982 Casanova et al., 1984). Effective photoreactive conjugation was found to occur after irradiation with UV light at 254 or 310 nm. 

Triiodothyronine is not classified as a thyroid inhibitor it is an amino acid derivative of thyronine and results from the oxidative coupling of monoiodotyrosyl and diiodotyrosyl residues. Iodine 131, the most often used radioisotope of I, is rapidly absorbed by the thyroid and is deposited in follicular colloid. Prom the site of its deposition, Bll causes fibrosis of the thyroid subsequent to pyknosis and necrosis of the follicular cells. 

Thyronines Tryptamine HPLC-hv-EC see arylalkylamines +0.85/+1.0 glassy carbon 241... 

Thyroxine (57) was rapidly photodeiodinated by light filtered to give wavelengths above 300 nm. In the first few minutes the main product was 3,3, 5-triiodothyronine, but by 15 min, 3,5-diiodothyronine and 3-iodothyronine were present in major amounts. There were also traces of 3,3, 5-triiodothyronine and 3,3 -diiodothyronine. In some runs traces of 3,3, 5 -triiodothyronine and 3, 5 -diiodothyronine were detected. Over 30 min the main product was 3-iodothyronine. Further deiodination to thyronine was very slow, presumably because the UV spectra had lower-wavelength maxima as iodine was removed. Similar photolysis of 3,3, 5-triiodothyronine for 10 min also gave 3,5-diiodo-... 

Triethylenetetramine [112-24-3] (+)-3,3, 5-Triiodo-L-thyronine 343 ID I(3)498B, N(1)267C YE6650000... 

The hormone triiodothyronine (T3) accelerates both total energy expenditure and protein degradation. The hormone secreted by the thyroid gland is thyroxine, which is converted to the active hormone T3 in a process that removes an iodine atom from the 5 position of the thyronine ring. If, however, an iodine atom is removed from the 3 position, the result is the formation of reverse-Ts... 

The thyroid hormone thyroxine (tetraiodo-thyronine, T4) and its active form triiodothyronine (T3) are derived from the amino acid tyrosine. The iodine atoms at positions 3 and 5 of the two phenol rings are characteristic of them. Post-translational synthesis of thyroxine takes place in the thyroid gland from tyrosine residues of the protein thyro-globulin, from which it is proteolytically cleaved before being released, iodothyronines are the only organic molecules in the animal organism that contain iodine. They increase the basal metabolic rate, partly by regulating mitochondrial ATP synthesis, in addition, they promote embryonic development. 

The most important pathway for the metabolism of T4 is monodeiodination. The removal of an iodide from the outer ring of T4 yields T3. Since the affinity of nuclear TRs is much higher for T3 than T4, outer ring monodeiodination of T4 to yield T3 produces a more active metabolite. Conversely, removal of an iodide from the inner ring of T4 yields an inactive metabolite, rTj. Both T3 and rT3 may undergo subsequent deiodinations to yield totally deiodinated thyronine (To). 

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