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Steven E Rokita - One of the best experts on this subject based on the ideXlab platform.
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redox control of Iodotyrosine deiodinase
Protein Science, 2019Co-Authors: Jimin Hu, Qi Su, J L Schlessman, Steven E RokitaAbstract:The redox chemistry of flavoproteins is often gated by substrate and Iodotyrosine deiodinase (IYD) has the additional ability to switch between reaction modes based on the substrate. Association of fluorotyrosine (F-Tyr), an inert substrate analog, stabilizes single electron transfer reactions of IYD that are not observed in the absence of this ligand. The co-crystal of F-Tyr and a T239A variant of human IYD have now been characterized to provide a structural basis for control of its flavin reactivity. Coordination of F-Tyr in the active site of this IYD closely mimics that of Iodotyrosine and only minor perturbations are observed after replacement of an active site Thr with Ala. However, loss of the side chain hydroxyl group removes a key hydrogen bond from flavin and suppresses the formation of its semiquinone intermediate. Even substitution of Thr with Ser decreases the midpoint potential of human IYD between its oxidized and semiquinone forms of flavin by almost 80 mV. This decrease does not adversely affect the kinetics of reductive dehalogenation although an analogous Ala variant exhibits a 6.7-fold decrease in its kcat /Km . Active site ligands lacking the zwitterion of halotyrosine are not able to induce closure of the active site lid that is necessary for promoting single electron transfer and dehalogenation. Under these conditions, a basal two-electron process dominates catalysis as indicated by preferential reduction of nitrophenol rather than deiodination of iodophenol.
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toward a halophenol dehalogenase from Iodotyrosine deiodinase via computational design
ACS Catalysis, 2018Co-Authors: Steven E RokitaAbstract:Reductive dehalogenation offers an attractive approach for removing halogenated pollutants from the environment, and Iodotyrosine deiodinase (IYD) may contribute to this process after it can be engineered to accept a broad range of substrates. The selectivity of IYD is controlled in part by an active site loop of ∼26 amino acids. In the absence of a substrate, the loop is disordered and only folds into a compact helix-turn-helix upon halotyrosine association. The design algorithm of Rosetta was applied to redesign this loop for response to 2-iodophenol rather than Iodotyrosine. One strategy using a restricted number of substitutions for increasing the inherent stability of the helical regions failed to generate variants with the desired properties. A series of point mutations identified strong epistatic interactions that impeded adaptation of IYD. This limitation was overcome by a second strategy that placed no restrictions on side-chain substitution by Rosetta. Nine representative designs containing betw...
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the distribution and mechanism of Iodotyrosine deiodinase defied expectations
Archives of Biochemistry and Biophysics, 2017Co-Authors: Qi Su, Steven E RokitaAbstract:Iodotyrosine deiodinase (IYD) is unusual for its reliance on flavin to promote reductive dehalogenation under aerobic conditions. As implied by the name, this enzyme was first discovered to catalyze iodide elimination from Iodotyrosine for recycling iodide during synthesis of tetra- and triiodothyronine collectively known as thyroid hormone. However, IYD likely supports many more functions and has been shown to debrominate and dechlorinate bromo- and chlorotyrosines. A specificity for halotyrosines versus halophenols is well preserved from humans to bacteria. In all examples to date, the substrate zwitterion establishes polar contacts with both the protein and the isoalloxazine ring of flavin. Mechanistic data suggest dehalogenation is catalyzed by sequential one electron transfer steps from reduced flavin to substrate despite the initial expectations for a single two electron transfer mechanism. A purported flavin semiquinone intermediate is stabilized by hydrogen bonding between its N5 position and the side chain of a Thr. Mutation of this residue to Ala suppresses dehalogenation and enhances a nitroreductase activity that is reminiscent of other enzymes within the same structural superfamily.
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active site binding is not sufficient for reductive deiodination by Iodotyrosine deiodinase
Biochemistry, 2017Co-Authors: Nattha Ingavat, Jennifer M Kavran, Steven E RokitaAbstract:The minimal requirements for substrate recognition and turnover by Iodotyrosine deiodinase were examined to learn the basis for its catalytic specificity. This enzyme is crucial for iodide homeostasis and the generation of thyroid hormone in chordates. 2-Iodophenol binds only very weakly to the human enzyme and is dehalogenated with a kcat/Km that is more than 4 orders of magnitude lower than that for Iodotyrosine. This discrimination likely protects against a futile cycle of iodinating and deiodinating precursors of thyroid hormone biosynthesis. Surprisingly, a very similar catalytic selectivity was expressed by a bacterial homologue from Haliscomenobacter hydrossis. In this example, discrimination was not based on affinity since 4-cyano-2-iodophenol bound to the bacterial deiodinase with a Kd lower than that of Iodotyrosine and yet was not detectably deiodinated. Other phenols including 2-iodophenol were deiodinated but only very inefficiently. Crystal structures of the bacterial enzyme with and without...
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functional analysis of Iodotyrosine deiodinase from drosophila melanogaster
Protein Science, 2016Co-Authors: Abhishek Phatarphekar, Steven E RokitaAbstract:The flavoprotein Iodotyrosine deiodinase (IYD) was first discovered in mammals through its ability to salvage iodide from mono- and diIodotyrosine, the by-products of thyroid hormone synthesis. Genomic information indicates that invertebrates contain homologous enzymes although their iodide requirements are unknown. The catalytic domain of IYD from Drosophila melanogaster has now been cloned, expressed and characterized to determine the scope of its potential catalytic function as a model for organisms that are not associated with thyroid hormone production. Little discrimination between iodo-, bromo-, and chlorotyrosine was detected. Their affinity for IYD ranges from 0.46 to 0.62 μM (Kd) and their efficiency of dehalogenation ranges from 2.4 – 9 x 103 M−1 s−1 (kcat/Km). These values fall within the variations described for IYDs from other organisms for which a physiological function has been confirmed. The relative contribution of three active site residues that coordinate to the amino acid substrates was subsequently determined by mutagenesis of IYD from Drosophila to refine future annotations of genomic and meta-genomic data for dehalogenation of halotyrosines. Substitution of the active site glutamate to glutamine was most detrimental to catalysis. Alternative substitution of an active site lysine to glutamine affected substrate affinity to the greatest extent but only moderately affected catalytic turnover. Substitution of phenylalanine for an active site tyrosine was least perturbing for binding and catalysis.
Jose C Moreno - One of the best experts on this subject based on the ideXlab platform.
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towards the pre clinical diagnosis of hypothyroidism caused by Iodotyrosine deiodinase dehal1 defects
Best Practice & Research Clinical Endocrinology & Metabolism, 2014Co-Authors: Ainhoa Iglesias, Laura Garcianimo, Jose Cocho A De Juan, Jose C MorenoAbstract:DEHAL1 (also named IYD) is the thyroidal enzyme that deiodinates mono- and diIodotyrosines (MIT, DIT) and recycles iodine, a scarce element in the environment, for the efficient synthesis of thyroid hormone. Failure of this enzyme leads to the Iodotyrosine deiodinase deficiency (ITDD), characterized by hypothyroidism, compressive goiter and variable mental retardation, whose diagnostic hallmark is the elevation of Iodotyrosines in serum and urine. However, the specific diagnosis of this type of hypothyroidism is not routinely performed, due to technical and practical difficulties in Iodotyrosine determinations. A handful of mutations in the DEHAL1 gene have been identified as the molecular basis for the ITDD. Patients harboring DEHAL1 defects so far described all belong to consanguineous families, and psychomotor deficits were present in some affected individuals. This is probably due to the lack of biochemical expression of the disease at the beginning of life, which causes ITDD being undetected in screening programs for congenital hypothyroidism, as currently performed. This worrying feature calls for efforts to improve pre-clinical detection of Iodotyrosine deiodinase deficiency during the neonatal time. Such a challenge poses questions of patho-physiological (natural history of the disease, environmental factors influencing its expression) epidemiological (prevalence of ITDD) and technical nature (development of optimal methodology for safe detection of pre-clinical ITDD), which will be addressed in this review.
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genetics and phenomics of hypothyroidism and goiter due to Iodotyrosine deiodinase dehal1 gene mutations
Molecular and Cellular Endocrinology, 2010Co-Authors: Jose C Moreno, Theo J VisserAbstract:Abstract Iodotyrosine deiodinase is a thyroidal enzyme that deiodinates mono- and di-Iodotyrosines (MIT, DIT) and recycles iodine, a scarce element in the environment, for the efficient synthesis of thyroid hormone. Failure of this enzyme leads to hypothyroidism, goiter and mental retardation, a clinical phenotype yet described in the 1950s, whose diagnostic hallmark is the elevation of Iodotyrosines in serum and urine. DEHAL1, the gene responsible for this activity, was recently isolated and the molecular basis for the Iodotyrosine deiodinase deficiency (ITDD) unraveled. The current clinical picture of mutations in DEHAL1 mostly recapitulates the “classical” phenotype of ITDD, including the psychomotor deficits. This is probably due to the lack of expression of the disease at the beginning of life, which causes ITDD being undetected in current screening programs for congenital hypothyroidism. This worrying feature calls for efforts to improve the preclinical detection of Iodotyrosine deiodinase deficiency in the neonatal time.
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mutations in the Iodotyrosine deiodinase gene and hypothyroidism
The New England Journal of Medicine, 2008Co-Authors: Jose C Moreno, Willem Klootwijk, Hans Van Toor, Graziella Pinto, Mariella Dalessandro, Aubene Leger, David Goudie, Michel Polak, Annette Gruters, Theo J VisserAbstract: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.
Francoise Courtin - One of the best experts on this subject based on the ideXlab platform.
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cloning and characterization of a novel isoform of Iodotyrosine dehalogenase 1 dehal1 dehal1c from human thyroid comparisons with dehal1 and dehal1b
Thyroid, 2006Co-Authors: Sedami Gnidehou, Renee Ohayon, Mariesophie Noelhudson, Stanislas Morand, Alphonse Sezan, Francoise Courtin, Ludovic Lacroix, Jacques Francon, Alain Virion, Corinne DupuyAbstract:The human Iodotyrosine dehalogenase 1 (DEHAL1) gene is composed of six exons. Two isoforms (DEHAL1 and DEHAL1B) have been published in GenBank, both of which have a nitroreductase domain and arise from differential splicing in exon 5. We recently showed that the DEHAL1 isoform is a transmembrane protein that efficiently catalyzes the NADPH-dependent deiodination of mono (L-MIT) and diIodotyrosine (L-DIT) in human embryonic kidney-293 (HEK293) cells. In the present study, we establish the existence of a new transcript, DEHAL1C, in the human thyroid with a terminal exon that lacks in the DEHAL1 transcript. This exon is the complete exon 5, which is spliced in the DEHAL1B mRNA variant. These two variants encode proteins with differing C-terminal domains. Using quantitative reverse transcription polymerase chain reaction, we found that the expression of the mRNA of DEHAL1C and DEHAL1B was lower than that of DEHAL1 mRNA in the thyroid. We also observed that human DEHAL1B and DEHAL1C proteins are rapidly degrad...
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Iodotyrosine dehalogenase 1 dehal1 is a transmembrane protein involved in the recycling of iodide close to the thyroglobulin iodination site
The FASEB Journal, 2004Co-Authors: Sedami Gnidehou, B Caillou, Monique Talbot, Renee Ohayon, Jacques Kaniewski, Mariesophie Noelhudson, Stanislas Morand, Diane Agnangji, Alphonse Sezan, Francoise CourtinAbstract:SPECIFIC AIMSIn the thyroid, Iodotyrosine dehalogenase acts on the mono (L-MIT) and diIodotyrosines (L-DIT) released during thyroglobulin hydrolysis and liberates iodide, which can then reenter hormone-producing pathways. This deiodinating activity is so efficient that only negligible amounts of Iodotyrosines are secreted by the thyroid. It has been reported that Iodotyrosine deiodination occurs predominantly in the microsomes and is mediated by NADPH. Recently, two cDNAs, 7,401 and 7,513-base-pairs long, and encoding proteins with a conserved nitroreductase domain were published in GenBank as Iodotyrosine dehalogenase 1 (DEHAL1) and Iodotyrosine dehalogenase 1B (DEHAL1B). Because the DEHAL1 protein has a complete nitroreductase domain, we chose to study the localization and the activity of this isoform first.PRINCIPAL FINDINGS1. DEHAL1 belongs to the nitroreductase familyA 7401 base pair cDNA, isolated from human thyroid was published in GenBank as Iodotyrosine dehalogenase protein mRNA (accession #AY259...
Theo J Visser - One of the best experts on this subject based on the ideXlab platform.
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genetics and phenomics of hypothyroidism and goiter due to Iodotyrosine deiodinase dehal1 gene mutations
Molecular and Cellular Endocrinology, 2010Co-Authors: Jose C Moreno, Theo J VisserAbstract:Abstract Iodotyrosine deiodinase is a thyroidal enzyme that deiodinates mono- and di-Iodotyrosines (MIT, DIT) and recycles iodine, a scarce element in the environment, for the efficient synthesis of thyroid hormone. Failure of this enzyme leads to hypothyroidism, goiter and mental retardation, a clinical phenotype yet described in the 1950s, whose diagnostic hallmark is the elevation of Iodotyrosines in serum and urine. DEHAL1, the gene responsible for this activity, was recently isolated and the molecular basis for the Iodotyrosine deiodinase deficiency (ITDD) unraveled. The current clinical picture of mutations in DEHAL1 mostly recapitulates the “classical” phenotype of ITDD, including the psychomotor deficits. This is probably due to the lack of expression of the disease at the beginning of life, which causes ITDD being undetected in current screening programs for congenital hypothyroidism. This worrying feature calls for efforts to improve the preclinical detection of Iodotyrosine deiodinase deficiency in the neonatal time.
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mutations in the Iodotyrosine deiodinase gene and hypothyroidism
The New England Journal of Medicine, 2008Co-Authors: Jose C Moreno, Willem Klootwijk, Hans Van Toor, Graziella Pinto, Mariella Dalessandro, Aubene Leger, David Goudie, Michel Polak, Annette Gruters, Theo J VisserAbstract: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.
Sedami Gnidehou - One of the best experts on this subject based on the ideXlab platform.
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cloning and characterization of a novel isoform of Iodotyrosine dehalogenase 1 dehal1 dehal1c from human thyroid comparisons with dehal1 and dehal1b
Thyroid, 2006Co-Authors: Sedami Gnidehou, Renee Ohayon, Mariesophie Noelhudson, Stanislas Morand, Alphonse Sezan, Francoise Courtin, Ludovic Lacroix, Jacques Francon, Alain Virion, Corinne DupuyAbstract:The human Iodotyrosine dehalogenase 1 (DEHAL1) gene is composed of six exons. Two isoforms (DEHAL1 and DEHAL1B) have been published in GenBank, both of which have a nitroreductase domain and arise from differential splicing in exon 5. We recently showed that the DEHAL1 isoform is a transmembrane protein that efficiently catalyzes the NADPH-dependent deiodination of mono (L-MIT) and diIodotyrosine (L-DIT) in human embryonic kidney-293 (HEK293) cells. In the present study, we establish the existence of a new transcript, DEHAL1C, in the human thyroid with a terminal exon that lacks in the DEHAL1 transcript. This exon is the complete exon 5, which is spliced in the DEHAL1B mRNA variant. These two variants encode proteins with differing C-terminal domains. Using quantitative reverse transcription polymerase chain reaction, we found that the expression of the mRNA of DEHAL1C and DEHAL1B was lower than that of DEHAL1 mRNA in the thyroid. We also observed that human DEHAL1B and DEHAL1C proteins are rapidly degrad...
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Iodotyrosine dehalogenase 1 dehal1 is a transmembrane protein involved in the recycling of iodide close to the thyroglobulin iodination site
The FASEB Journal, 2004Co-Authors: Sedami Gnidehou, B Caillou, Monique Talbot, Renee Ohayon, Jacques Kaniewski, Mariesophie Noelhudson, Stanislas Morand, Diane Agnangji, Alphonse Sezan, Francoise CourtinAbstract:SPECIFIC AIMSIn the thyroid, Iodotyrosine dehalogenase acts on the mono (L-MIT) and diIodotyrosines (L-DIT) released during thyroglobulin hydrolysis and liberates iodide, which can then reenter hormone-producing pathways. This deiodinating activity is so efficient that only negligible amounts of Iodotyrosines are secreted by the thyroid. It has been reported that Iodotyrosine deiodination occurs predominantly in the microsomes and is mediated by NADPH. Recently, two cDNAs, 7,401 and 7,513-base-pairs long, and encoding proteins with a conserved nitroreductase domain were published in GenBank as Iodotyrosine dehalogenase 1 (DEHAL1) and Iodotyrosine dehalogenase 1B (DEHAL1B). Because the DEHAL1 protein has a complete nitroreductase domain, we chose to study the localization and the activity of this isoform first.PRINCIPAL FINDINGS1. DEHAL1 belongs to the nitroreductase familyA 7401 base pair cDNA, isolated from human thyroid was published in GenBank as Iodotyrosine dehalogenase protein mRNA (accession #AY259...
