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The metabolism and de-bromination of bromotyrosine in vivo

Mani, AR; Moreno, JC; Visser, TJ; Moore, KP; (2016) The metabolism and de-bromination of bromotyrosine in vivo. Free Radical Biology and Medicine , 90 pp. 243-251. 10.1016/j.freeradbiomed.2015.11.030. Green open access

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Abstract

During inflammation, leukocyte-derived eosinophil peroxidase catalyses the formation of hypobromous acid, which can brominate tyrosine residues in proteins to form bromotyrosine. Since eosinophils are involved in the pathogenesis of allergic reactions, such as asthma, urinary bromotyrosine level has been used for the assessment of children with asthma. However, little is known about the metabolism and disposition of bromotyrosine in vivo. The aim of this study was to identify the major urinary metabolites formed during bromotyrosine metabolism and to develop mass spectrometric methods for their quantitation. Deuterium-labeled bromotyrosine was synthesized by deuterium exchange. [D3]bromotyrosine (500nmole) was injected intraperitoneally into Sprague-Dawley rats and urine was collected for 24h in a metabolic cage. (13)C-labeled derivatives of bromotyrosine and its major urinary metabolite were synthesized and used as internal standards for quantitation. Following solid phase extraction, urine samples were derivatized to the pentafluorobenzyl ester, and analyzed using isotope dilution gas chromatography and negative-ion chemical ionization mass spectrometry. A novel brominated metabolite, 3-bromo-4-hydroxyphenylacetic acid (bromo-HPA), was identified as the major brominated metabolite of bromotyrosine. Bromo-HPA only accounted for 0.43±0.04% of infused [D3]bromotyrosine and 0.12±0.02% of infused [D3]bromotyrosine was excreted in the urine unchanged. However, ~1.3% (6.66±1.33nmole) of infused [D3]bromotyrosine was excreted in the urine as the de-brominated metabolite, [D3]4-hydroxyphenylacetic acid, which is also a urinary metabolite of tyrosine in mammals. We also tested whether or not iodotyrosine dehalogenase can catalyse de-bromination of bromotyrosine and showed that iodotyrosine dehalogenase is able to de-brominate free bromotyrosine in vitro. We identified bromo-HPA as the main brominated urinary metabolite of bromotyrosine in rats. However, de-halogenation of bromotyrosine is the major metabolic pathway to eliminate free brominated tyrosine in vivo.

Type: Article
Title: The metabolism and de-bromination of bromotyrosine in vivo
Location: United States
Open access status: An open access version is available from UCL Discovery
DOI: 10.1016/j.freeradbiomed.2015.11.030
Publisher version: http://dx.doi.org/10.1016/j.freeradbiomed.2015.11....
Language: English
Additional information: © 2015 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
Keywords: 3-Bromo-4-hydroxyphenylacetic acid, 4-Hydroxyphenylacetic acid, Bromotyrosine, De-halogenation, Urine
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Medical Sciences > Div of Medicine > Department of Education
URI: https://discovery.ucl.ac.uk/id/eprint/1476534
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