Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

3,5,3'-triiodotyronine formation was studied in vitro after iodination of goiter thyroglobulin catalyzed by purified thyroid peroxidase. A fractionnal number of T3 is always obtained per mole of thyroglobulin in both in vitro and in vivo. This result cannot be explained by a heterogeneity in thyroglobulin iodination or in a partial conversion of T3 to T4. It is suggested that thyroglobulin is heterogenous either in its primary sequence or in its teritiary configuration. Thyroglobulin contains tyrosine residues which are specific for the T3 formation and moreover T3 is not the precursor of T4. The efficiency of T3 formation was studied: the maximal number of T3 molecules is obtained with 30 iodine atoms per mole of thyroglobulin. In addition the results suggest that the tyrosines which are coupled with a high efficiency are iodinated sequentially.
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PMID:[In vitro synthesis of 3,5,3'-triiodothyronine catalyzed by thyroid peroxidase (author's transl)]. 65 17

Two patients (G2, G3) with iodine organification defect were studied. The first patient (G2), a 25-year-old women with no clinical hypothyroidism, had had her goiter for 10 years; 62% of the thyroidal iodine was released by perchlorate indicating iodine organification defect. The thyroid tissue obtained at thyroidectomy contained a normal concentration of thyroid peroxidase (I2 formation from I-) when tested after solubilization of the enzyme by trypsin and digitonin treatment of the particulate material. 1. The enzymatic activity (G2-TPO) behaved on DEAE cellulose chromatography very differently from those of hog (P-TPO) or another human goiter peroxidase (G1-TPO) (Pommier, et al., J Clin Endocrinol Metab 39: 69, 1974): the molarity of elution was 2M NaCl instead of 0.15 mM. 2. Both P-TPO and G2-TPO catalyzed iodide peroxidation (I- leads to I2) but the Km (iodide) value for G2-TPO was much lower (2.3 x 10(-2) M) when compared with that of P-TPO (3.7 x 10(-3) M) or G1-TPO (3.5 x 10(-3) M). In addition, the optimum pH for this reaction differed markedly (pH 6.1 instead of 7.9). 3. G2-TPO was poorly efficient in catalyzing the oxidation of gaiacol to tetragaiacol. 4. G2-TPO was unable to perform the iodination of non-iodinated goiter thyroglobulin whatever the pH and the iodide concentration. 5. Thyroglobulin from this goiter (G2) was almost not iodinated (0.0014%), i.e., 0.07 atoms iodine/mole thyroglobulin), and its total content in the gland was very low (0.3-4 g/1000 g wet tissue instead of 25 g). A clear discrepancy was thus shown between the euthyroid state of this patient and the total lack of iodinating activity of the isolated peroxidase. The second patient (G3), a 17-year-old man with clinical hypothyroidism, had had his goiter for 5 years. 100% of the thyroidal iodine was released by perchlorate indicating a complete iodine organification defect. The thyroid tissue obtained at thyroidectomy contained no peroxidase activity when tested before and after treatment of the particulate material by trypsin and digitonin and even in the presence of hematin. Thyroglobulin from this goiter, which was almost non-iodinated (0.0014%), was present in normal amounts in the gland (congruent to 25 g/1000 g).
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PMID:Thyroid iodine organification defects: a case with lack of thyroglobulin iodination and a case without any peroxidase activity. 126 32

The content and distribution of iodoamino acids in thyroglobulin of the cryopreserved thyrotoxically-changed thyroid parenchyma were studied, as was thyroglobulin iodination. Thyroid tissue obtained during operations of patients with diffuse-toxic goiter was investigated. The thyroid parenchyma was cryopreserved according to the method developed at the Institute of Cryobiology and Cryomedicine Problems, Academy of Sciences of the Ukrainian SSR. The tissues were stored for 4-6 months. Thyroglobulin was isolated by gel filtration of the thyroid saline extract through a column packed with Sephadex G-200. Thyroglobulin was iodinated with KI + I2 water solution, pH 9.2, at 37 C for 30 min. The amount of iodine added was 100 moles of I2 per protein mole. Protein concentration was determined by the biuret reaction. Thyroglobulin iodoamino acid composition was determined by direct spectrophotometry. Absorption spectra were measured by an EPS-3T recording spectrophotometer ("Hitachi", Japan). The processes of freezing (-196 degrees C) and thawing of the thyroid parenchyma were shown to induce no changes in the thyroglobulin iodoamino acid composition. Cryopreservation of the thyroid parenchyma considerably affected iodine incorporation and formation of iodoamino acids in the thyroglobulin during its in vitro iodination. It may be supposed that cryopreservation of the thyroid tissue affects the thyroglobulin conformational status, that results in increased iodination of this iodoprotein.
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PMID:[Effect of cryopreservation of thyroid parenchyma on iodoamino acid composition of thyroglobulin and its iodination]. 398 96