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The Biochemical Journal Jan 1972Insulin dissolved in aqueous or methanolic buffer was iodinated to give preparations containing an average of between one and five iodine atoms per insulin monomer. The...
Insulin dissolved in aqueous or methanolic buffer was iodinated to give preparations containing an average of between one and five iodine atoms per insulin monomer. The resultant preparations were fragmented in various ways and the ratio of tyrosine to monoiodotyrosine and di-iodotyrosine was determined in each fragment. This has allowed the distribution of iodine between the combined A-chain tyrosine residues and the individual B-chain tyrosine residues to be determined. The hormonal activity of each of these iodinated insulin preparations was measured from their effect on the production of (14)CO(2) from [1-(14)C]glucose by isolated adipose cells. The results were interpreted as meaning that the iodination of tyrosine residue A19 or B16 leads to the inactivation of insulin. Speculations are made about the nature of an interaction between insulin and a receptor site on the target tissue.
Topics: Animals; Biological Assay; Carbon Dioxide; Carbon Isotopes; Glucose; In Vitro Techniques; Insulin; Iodine; Methanol; Monoiodotyrosine; Receptors, Drug; Tyrosine
PubMed: 5075226
DOI: 10.1042/bj1260123 -
Toxicological Sciences : An Official... Dec 2018The enzyme iodotyrosine deiodinase (dehalogenase, IYD) catalyzes iodide recycling and promotes iodide retention in thyroid follicular cells. Loss of function or chemical...
The enzyme iodotyrosine deiodinase (dehalogenase, IYD) catalyzes iodide recycling and promotes iodide retention in thyroid follicular cells. Loss of function or chemical inhibition of IYD reduces available iodide for thyroid hormone synthesis, which leads to hormone insufficiency in tissues and subsequent negative developmental consequences. IYD activity is especially critical under conditions of lower dietary iodine and in low iodine environments. Our objective was to evaluate the toxicological relevance of IYD inhibition in a model amphibian (Xenopus laevis) used extensively for thyroid disruption research. First, we characterized IYD ontogeny through quantification of IYD mRNA expression. Under normal development, IYD was expressed in thyroid glands, kidneys, liver, and intestines, but minimally in the tail. Then, we evaluated how IYD inhibition affected developing larval X. laevis with an in vivo exposure to a known IYD inhibitor (3-nitro-l-tyrosine, MNT) under iodine-controlled conditions; MNT concentrations were 7.4-200 mg/L, with an additional 'rescue' treatment of 200 mg/L MNT supplemented with iodide. Chemical inhibition of IYD resulted in markedly delayed development, with larvae in the highest MNT concentrations arrested prior to metamorphic climax. This effect was linked to reduced glandular and circulating thyroid hormones, increased thyroidal sodium-iodide symporter gene expression, and follicular cell hypertrophy and hyperplasia. Iodide supplementation negated these effects, effectively rescuing exposed larvae. These results establish toxicological relevance of IYD inhibition in amphibians. Given the highly conserved nature of the IYD protein sequence and scarcity of environmental iodine, IYD should be further investigated as a target for thyroid axis disruption in freshwater organisms.
Topics: Animals; Iodide Peroxidase; Iodides; Larva; Metamorphosis, Biological; Monoiodotyrosine; RNA, Messenger; Symporters; Thyroid Gland; Thyroid Hormones; Tyrosine; Xenopus laevis
PubMed: 30137636
DOI: 10.1093/toxsci/kfy203 -
The Journal of Biological Chemistry Jan 2015Reductive dehalogenation is not typical of aerobic organisms but plays a significant role in iodide homeostasis and thyroid activity. The flavoprotein iodotyrosine...
Reductive dehalogenation is not typical of aerobic organisms but plays a significant role in iodide homeostasis and thyroid activity. The flavoprotein iodotyrosine deiodinase (IYD) is responsible for iodide salvage by reductive deiodination of the iodotyrosine derivatives formed as byproducts of thyroid hormone biosynthesis. Heterologous expression of the human enzyme lacking its N-terminal membrane anchor has allowed for physical and biochemical studies to identify the role of substrate in controlling the active site geometry and flavin chemistry. Crystal structures of human IYD and its complex with 3-iodo-l-tyrosine illustrate the ability of the substrate to provide multiple interactions with the isoalloxazine system of FMN that are usually provided by protein side chains. Ligand binding acts to template the active site geometry and significantly stabilize the one-electron-reduced semiquinone form of FMN. The neutral form of this semiquinone is observed during reductive titration of IYD in the presence of the substrate analog 3-fluoro-l-tyrosine. In the absence of an active site ligand, only the oxidized and two-electron-reduced forms of FMN are detected. The pH dependence of IYD binding and turnover also supports the importance of direct coordination between substrate and FMN for productive catalysis.
Topics: Biocatalysis; Catalytic Domain; Crystallography, X-Ray; Electron Transport; Electrons; Escherichia coli; Flavin Mononucleotide; Flavins; Gene Expression; Humans; Hydrogen-Ion Concentration; Iodide Peroxidase; Iodides; Models, Molecular; Monoiodotyrosine; Oxidation-Reduction; Protein Binding; Recombinant Proteins; Substrate Specificity; Tyrosine
PubMed: 25395621
DOI: 10.1074/jbc.M114.605964 -
The Biochemical Journal Nov 1975(125)I-labelled asialo-fetuin, administered intravenously, rapidly accumulates in rat liver and the radioactivity is subsequently cleared from the liver within 60min....
(125)I-labelled asialo-fetuin, administered intravenously, rapidly accumulates in rat liver and the radioactivity is subsequently cleared from the liver within 60min. Plasma radioactivity reaches a minimum between 10 and 15 min after injection and rises slightly during the period of liver clearance. Free iodide is the only radioactive compound found in plasma during this latter period. Fractionation of rat liver at 5 and 13min after injection of (125)I-labelled asialo-fetuin supports the hypothesis that asialo-glycoprotein is taken into liver by pinocytosis after binding to the plasma membrane and is then hydrolysed by lysosomal enzymes. At 5min, radioactivity was concentrated 23-fold in a membrane fraction similarly enriched in phosphodiesterase I, a plasma-membrane marker enzyme, whereas at 13min the radioactivity appeared to be localized within lysosomes. Separation of three liver fractions (heavy mitochondrial, light mitochondrial and microsomal) on sucrose gradients revealed the presence of two populations of radioactive particles. One population banded in a region coincident with a lysosomal marker enzyme. The other, more abundant, population of radioactive particles had a density of 1.13 and contained some phosphodiesterase, but very little lysosomal enzyme. These latter particles appear to be pinocytotic vesicles produced after uptake of the asialo-fetuin bound by the plasma membrane. Lysosomal extracts extensively hydrolyse asialo-fetuin during incubation in vitro at pH4.7 and iodotyrosine is completely released from the iodinated glycoprotein. Protein digestion within lysosomes was demonstrated by incubating intact lysosomes containing (125)I-labelled asialo-fetuin in iso-osmotic sucrose, pH7.2. The radioactive hydrolysis product, iodotyrosine, readily passed through the lysosomal membrane and was found in the external medium. These results are not sufficient to account for the presence of free iodide in plasma, but this was explained by the observation that iodotyrosines are deiodinated by microsomal enzymes in the presence of NADPH.
Topics: Animals; Cell Membrane; Centrifugation, Isopycnic; Chromatography, Gel; Esterases; Fetal Proteins; Glycoproteins; Iodides; Liver; Lysosomes; Male; Monoiodotyrosine; NAD; Phosphoric Diester Hydrolases; Pinocytosis; Proteins; Rats; alpha-Fetoproteins
PubMed: 56934
DOI: 10.1042/bj1520271 -
PloS One 2012Homeothermal animals, such as mammals, maintain their body temperature by heat generation and heat dissipation, while poikilothermal animals, such as insects, accomplish...
Homeothermal animals, such as mammals, maintain their body temperature by heat generation and heat dissipation, while poikilothermal animals, such as insects, accomplish it by relocating to an environment of their favored temperature. Catecholamines are known to regulate thermogenesis and metabolic rate in mammals, but their roles in other animals are poorly understood. The fruit fly, Drosophila melanogaster, has been used as a model system for the genetic studies of temperature preference behavior. Here, we demonstrate that metabolic rate and temperature sensitivity of some temperature sensitive behaviors are regulated by dopamine in Drosophila. Temperature-sensitive molecules like dTrpA1 and shi(ts) induce temperature-dependent behavioral changes, and the temperature at which the changes are induced were lowered in the dopamine transporter-defective mutant, fumin. The mutant also displays a preference for lower temperatures. This thermophobic phenotype was rescued by the genetic recovery of the dopamine transporter in dopamine neurons. Flies fed with a dopamine biosynthesis inhibitor (3-iodo-L-tyrosine), which diminishes dopamine signaling, exhibited preference for a higher temperature. Furthermore, we found that the metabolic rate is up-regulated in the fumin mutant. Taken together, dopamine has functions in the temperature sensitivity of behavioral changes and metabolic rate regulation in Drosophila, as well as its previously reported functions in arousal/sleep regulation.
Topics: Animals; Dopamine; Dopamine Plasma Membrane Transport Proteins; Dopaminergic Neurons; Drosophila Proteins; Drosophila melanogaster; Environment; Metabolism; Monoiodotyrosine; Temperature
PubMed: 22347491
DOI: 10.1371/journal.pone.0031513 -
The Journal of Biological Chemistry Jan 1997A fragment of bovine thyroglobulin encompassing residues 1218-1591 was prepared by limited proteolysis with thermolysin and continuous-elution polyacrylamide gel...
A fragment of bovine thyroglobulin encompassing residues 1218-1591 was prepared by limited proteolysis with thermolysin and continuous-elution polyacrylamide gel electrophoresis in SDS. The reduced and carboxymethylated peptide was digested with endoproteinase Asp-N and fractionated by reverse-phase high performance liquid chromatography. The fractions were analyzed by electrospray and fast atom bombardment mass spectrometry in combination with Edman degradation. The post-translational modifications of all seven tyrosyl residues of the fragment were characterized at an unprecedented level of definition. The analysis revealed the formation of: 1) monoiodotyrosine from tyrosine 1234; 2) monoiodotyrosine, diiodotyrosine, triiodothyronine (T3), and tetraiodothyronine (thyroxine, T4) from tyrosine 1291; and 3) monoiodotyrosine, diiodotyrosine, and dehydroalanine from tyrosine 1375. Iodothyronine formation from tyrosine 1291 accounted for 10% of total T4 of thyroglobulin (0.30 mol of T4/mol of 660-kDa thyroglobulin), and 8% of total T3 (0.08 mol of T3/mol of thyroglobulin). This is the first documentation of the hormonogenic nature of tyrosine 1291 of bovine thyroglobulin, as thyroxine formation at a corresponding site was so far reported only in rabbit, guinea pig, and turtle thyroglobulin. This is also the first direct identification of tyrosine 1375 of bovine thyroglobulin as a donor residue. It is suggested that tyrosyl residues 1291 and 1375 may support together the function of an independent hormonogenic domain in the mid-portion of the polypeptide chain of thyroglobulin.
Topics: Amino Acid Sequence; Animals; Cattle; Chromatography, High Pressure Liquid; Mass Spectrometry; Molecular Sequence Data; Peptide Fragments; Protein Processing, Post-Translational; Thermolysin; Thyroglobulin; Thyroxine; Triiodothyronine; Tyrosine
PubMed: 8995307
DOI: 10.1074/jbc.272.1.639 -
The Journal of Clinical Investigation Jun 1973A specific and reproducible double antibody radioimmunoassay for the measurement of thyroglobulin (HTg) in human serum has been developed. Since antithyroglobulin...
A specific and reproducible double antibody radioimmunoassay for the measurement of thyroglobulin (HTg) in human serum has been developed. Since antithyroglobulin autoantibodies combine with the [(131)I] HTg tracer, antibody-positive sera were rejected for measurement. Specificity is demonstrated in that thyroid analogous such as thyroxine (T(4)), triiodothyronine (T(2)) monoiodotyrosine (MIT) and diiodotyrosine (DIT) did not crossreact. Sera previously reacted with anti-HTg-Sepharose contained no immunoassayable HTg. Finally, sera obtained from patients after total thyroid ablation for thyroid carcinoma did not contain demonstrable HTg. The sensitivity of the assay is 1.6 ng/ml, and HTg was detectable in 74% of 95 normal subjects. The mean concentration was 5.1 ng/ml +/-0.49 SEM (range <1.6-20.7 ng/ml). Day to day variation in HTg levels is large in some euthyroid subjects and nearly absent in others. HTg was detectable in 90% of the sera obtained in 23 pregnant women at delivery in whom a mean concentration of 10.1 ng/ml +/-1.3 SEM was observed. The mean level for the corresponding newborn infants at birth was 29.3 ng/ml +/-4.7 SEM a value significantly higher than the mean maternal HTg concentration (P <0.01). A group of 17 thyrotoxic individuals all had elevated HTg levels; the mean for this group was 344.8 ng/ml +/-90.7 SEM. In the acute phase of subacute thyroiditis HTg was also elevated in all of 12 patients, and the mean for this group was 136.8 ng/ml +/-74.6 SEM.
Topics: Adolescent; Adult; Animals; Blood Protein Electrophoresis; Centrifugation, Density Gradient; Chromatography, Ion Exchange; Cross Reactions; Female; Graves Disease; Humans; Hyperthyroidism; Immunoelectrophoresis; Infant, Newborn; Iodine Radioisotopes; Male; Pregnancy; Protein Binding; Rabbits; Radioimmunoassay; Thyroglobulin; Thyroiditis
PubMed: 4739914
DOI: 10.1172/JCI107303 -
Anatomical Record (Hoboken, N.J. : 2007) Jul 2008This paper details linear hair re-growth patterns observed in rats. Adult rats were shaved and observed. The first wave of hair re-growth did not distribute everywhere,...
This paper details linear hair re-growth patterns observed in rats. Adult rats were shaved and observed. The first wave of hair re-growth did not distribute everywhere, but along specific craniocaudally-oriented lines. The hair-lines were 2-15 mm wide and ran from the head, through the torso to the limbs, and were symmetrical along the left and right sides of the body. The symmetric hair-lines from both sides of the body converged around the mouth, nose, and at the pubic region or ventral midline to form a system of hair-loop-lines (HLLs). The loops can be differentiated into four main patterns. The Dorsal Loop and the Lateral Dorsal Loop run along the dorsum and hindlimb. The Ventral Loop and Lateral Ventral Loop travel along the thorax, abdomen, and forelimb. These hair-lines coincide with our previously observed sympathetic-substance lines (SSLs) in the rat's skin. Histological observation indicates that rat hair follicles along the hair-lines were at anagen phase. The catecholamine histofluorescent check showed abundant sympathetic nerve fibers beneath the hair-lines. After the rats' hairs were dyed, and selected portions shaved, re-growth was only observed on the shaved portions, indicating that the linear hair growth closely correlated with the shaving. Lastly we examine the cause of the preferential re-growth and briefly discuss the purpose and physiological role of the HLL.
Topics: Age Factors; Animals; Autoradiography; Catecholamines; Female; Hair; Iodine Radioisotopes; Male; Monoiodotyrosine; Nerve Fibers; Radionuclide Imaging; Radiopharmaceuticals; Rats; Rats, Wistar; Skin
PubMed: 18543289
DOI: 10.1002/ar.20702 -
International Journal of Molecular... Nov 2013Planaria are the simplest organisms with bilateral symmetry and a central nervous system (CNS) with cephalization; therefore, they could be useful as model organisms to...
Planaria are the simplest organisms with bilateral symmetry and a central nervous system (CNS) with cephalization; therefore, they could be useful as model organisms to investigate mechanistic aspects of parkinsonism and to screen potential therapeutic agents. Taking advantage of the organism's anti-tropism towards light, we measured a significantly reduced locomotor velocity in planaria after exposure to 3-iodo-L-tyrosine, an inhibitor of tyrosine hydroxylase that is an enzyme catalyzing the first and rate-limiting step in the biosynthesis of catecholamines. A simple semi-automatic assay using videotaped experiments and subsequent evaluation by tracking software was also implemented to increase throughput. The dopaminergic regulation of locomotor velocity was confirmed by bromocriptine, a drug whose mechanisms of action to treat Parkinson's disease is believed to be through the stimulation of nerves that control movement.
Topics: Animals; Bromocriptine; Humans; Light; Locomotion; Models, Animal; Monoiodotyrosine; Parkinson Disease; Planarians; Protein Binding; Receptors, Dopamine; Tyrosine 3-Monooxygenase
PubMed: 24287905
DOI: 10.3390/ijms141223289 -
The New England Journal of Medicine Apr 2008DEHAL1 has been identified as the gene encoding iodotyrosine deiodinase in the thyroid, where it controls the reuse of iodide for thyroid hormone synthesis. We screened...
DEHAL1 has been identified as the gene encoding iodotyrosine deiodinase in the thyroid, where it controls the reuse of iodide for thyroid hormone synthesis. We screened patients with hypothyroidism who had features suggestive of an iodotyrosine deiodinase defect for mutations in DEHAL1. Two missense mutations and a deletion of three base pairs were identified in four patients from three unrelated families; all the patients had a dramatic reduction of in vitro activity of iodotyrosine deiodinase. Patients had severe goitrous hypothyroidism, which was evident in infancy and childhood. Two patients had cognitive deficits due to late diagnosis and treatment. Thus, mutations in DEHAL1 led to a deficiency in iodotyrosine deiodinase in these patients. Because infants with DEHAL1 defects may have normal thyroid function at birth, they may be missed by neonatal screening programs for congenital hypothyroidism.
Topics: Adult; Amino Acid Sequence; Child; DNA Mutational Analysis; Female; Frameshift Mutation; Goiter; Homozygote; Humans; Hypothyroidism; Iodide Peroxidase; Male; Middle Aged; Molecular Sequence Data; Monoiodotyrosine; Mutation, Missense; Open Reading Frames; Phenotype; Polymerase Chain Reaction; Sequence Deletion
PubMed: 18434651
DOI: 10.1056/NEJMoa0706819