Diiodo-L-tyrosine

Chemical Name 0-(4-hydroxy-3-iodophenyl)-3,5-diiodo-L-tyrosine... 

Several compounds can be oxidized by peroxidases by a free radical mechanism. Among various substrates of peroxidases, L-tyrosine attracts a great interest as an important phenolic compound containing at 100 200 pmol 1 1 in plasma and cells, which can be involved in lipid and protein oxidation. In 1980, Ralston and Dunford [187] have shown that HRP Compound II oxidizes L-tyrosine and 3,5-diiodo-L-tyrosine with pH-dependent reaction rates. Ohtaki et al. [188] measured the rate constants for the reactions of hog thyroid peroxidase Compounds I and II with L-tyrosine (Table 22.1) and showed that Compound I was reduced directly to ferric enzyme. Thus, in this case the reaction of Compound I with L-tyrosine proceeds by two-electron mechanism. In subsequent work these authors have shown [189] that at physiological pH TPO catalyzed the two-electron oxidation not only L-tyrosine but also D-tyrosine, A -acetyltyrosinamide, and monoiodotyrosine, whereas diiodotyrosine was oxidized by a one-electron mechanism. 

Oza VB, Salamonczyk GM, Guo Z, Sih CJ (1997) Model Reactions of Thyroxine Biosynthesis. Identification of the Key Intermediates in Thyroxine Formation from 3,5-Diiodo-L-tyrosine and 4-FIydroxy-3,5-diiodophenylpyruvic Acid. J Am Chem Soc 119 11315... 

C20H14O3 (-t-)-BP-7b,8a-diol-9a, 10a-epoxide 2 63323-31-9 25.00 1.2374 2 32126 C20H20I2N205 N-acetyl-L-phenylalan -3,5-diiodo-L-tyrosine 3786-011 Hl T202O n... 

Liothyronine, 0-(4-Hydroxy-3 iodophenyl)-3,5-diiodo-L-tyrosine L-3-[4-(4-hydroxy-3-iodophertoxy)-3,5-diiodophenyljalanine 4 -(3 -iodo -4 -hydroxyphenoxy) -3,5 -diiodophenylalanine 3,5,3 -triiodothyronine T-3 Triothy-rone. C HyljNO mol wt 651.01. C 27 68%, H 1.86%, I 58.48%, N 2.15%, O 9.33%, Amino acid found in human plasma and thyroid gland, similar to thyroxine q-v. Gross, Pitt-Rivers, Lancet 1952, I, 439. Formation from diiodo-thyronine Roche et al., Biockem. Blophys. Acta 11, 215... 

The thyroid gland also contains two quantitatively important iodinated amino acids, diiodo-L-tyrosine (DIT) and monoiodo-L-tyrosine (MIT). In addition, there are small amounts of other iodothyronines, such as 3,3 -diiodo-L-thyronine (T2) and 3,3, 5 -triiodo-L-thyronine (reverse T3 [rTs]). None of the latter compounds possesses any significant hormonal activity. Chemically, MIT is 3-iodo-L-tyrosine, and DIT is 3,5-diiodo-L-tyrosine. The coupling of the two outer rings of DIT or of one outer ring of DIT with that of MIT (each with the net loss of... 

Optically Active. Glycyl-l-tyrosine. Glycyl-d-alanine. Glycyl-d-tryptophane. Glycyl-l-phenylalanine. Glycyl-3, 5-diiodo-l-tyrosine. dl-Alanyl-d-alanine. 1-AlanyI-glycine. d-Alanyl-d-alanine. d-AIanyl-l-leucine. d-Alanyl-d-tryptophane. 

The iodinated amino acids which have been identified to date in the thyroid gland are 3-monoiodo-L-tyrosine or MIT (8,38,40,62), 3,5-diiodo-L-tyrosine or DIT (9,20), 3,5,3 -triiodo-L-thyronine or TRITh (17,41,42), 3,5,3, 5 -tetraiodo-L-thyronine or thyroxine or Tx (19,24), and 2 (or 4)-monoiodo-L-histidine or MIH (43). TRITh and Tx are the two constituents of the thyroid hormone MIT and DIT are their precursors. The formation of all of these iodo derivatives during the hormone genesis, their secretion, the circulation of some of them in blood, and their metabolism can be followed by radiochromatography and, for certain problems, by paper electrophoresis. 

Diiodo-L-tyrosine and L-thyroxine were considered, up to 1947, to be the only iodinated amino acids of thyroglobulin. MIT, MIH, TRITh, and, eventually, traces of a DITh in this protein have been characterized in the last five years by the use of radiochromatography. 

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