DOCSLIB.ORG

The Enterohepatic Circulation of Glutathione

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Enterohepatic Circulation of Glutathione THE ENTEROHEPATIC CIRCULATION OF GLUTATHIONE CONJUGATES OF XENOBIOTICS IN THE RAT BY MARTIN ALEXANDER PUE Being a thesis submitted for the degree of Doctor of Philosophy in the University of London October, 1983 Department of Biochemistry St. Mary's Hospital Medical School Paddington London CONTENTS Page No. ABSTRACT 3 ACKNOWLEDGEMENTS 5 ABBREVIATIONS 6 CHAPTER 1 INTRODUCTION 9 CHAPTER 2 GENERAL MATERIALS AND METHODS 85 CHAPTER 3 GLUTATHIONE CONJUGATION AND ENTERO- 95 HEPATIC CIRCULATION IN THE METABOLISM OF NAPHTHALENE CHAPTER 4 GLUTATHIONE CONJUGATION AND ENTERO- 14-1 HEPATIC CIRCULATION IN THE METABOLISM OF 1-CHL0R0-2,4-DINITROBENZENE CHAPTER 5 GLUTATHIONE CONJUGATION AND ENTERO- 176 HEPATIC CIRCULATION IN THE METABOLISM OF BROMSULPHTHALEIN CHAPTER 6 IN VITRO METABOLISM OF GLUTATHIONE CON- 193 JUGATES CHAPTER 7 GENERAL DISCUSSION 220 REFERENCES 240 - 2 - ABSTRACT The relationships between the excretion of xenobiotics in bile as glutathione S-conjugates and in urine as mercapturic acids have been investigated in the rat using three compounds, naphthalene, 1-chloro-2,4- dinitrobenzene and bromsulphthalein. These three compounds have been shown to be excreted in the bile of rats as the respective glutathione S-derivatives following intra- venous administration of the parent xenobiotic. Following intra- duodenal administration of the radiolabelled glutathione S-conjugates of naphthalene and 1-chloro-2,4-dinitrobenzene, radioactive metabolites were absorbed from the gastrointestinal tract and excreted in urine, especially, and in bile, principally as the corresponding mercapturic acids. Absorption and biliary excretion of material derived from the infused glutathione conjugates was observed to be rapid. A very low absorption and excretion of metabolites derived from bromsulphthalein- glutathione was observed i.e. metabolites of bromsulphthalein showed negligible enterohepatic circulation. The mechanisms involved in the enterohepatic circulation of the glutathione S-conjugates of naphthalene and 1-chloro-2,4-dinitro- benzene were investigated. Intestinal bacteria did not seem to be involved in the absorption and metabolism of these conjugates, since oral antibiotic-pretreatment of rats did not significantly alter the enterohepatic recycling of material derived from the conjugates. Possible tissue sites for the metabolism of the glutathione conjugates of naphthalene and 1-chloro-2,4-dinitrobenzene were investigated in - 3 - incubations of isolated kidney, small intestine and liver cells. Isolated kidney cells extensively hydrolysed both S-(1,2-dihydrohydroxy- naphthyl)glutathione and S-(2,4-dinitrophenyl)glutathione to the respective cysteine derivatives. Kidney cells were also active in the formation of the mercapturic acid derivative of naphthalene. Isolated small intestinal and liver cells metabolised the glutathione S-conju- gates to the corresponding cysteine derivatives, although at significantly lower rates than kidney cells. The extent of hydrolysis of the glutathione conjugates by the isolated cell preparations was in agreement with the activity of y-glutamyltransferase measured for the different cell types. The metabolic cooperation of the kidney, small intestine and liver in the metabolism of glutathione S-conjugates and excretion as mercapturic acids is discussed in the light of the results presented and data in the literature. - 4 - ACKNOWLEDGEMENTS I would like to thank the Department of Biochemistry, St. Mary's Hospital Medical School, London, and my supervisor, Dr. Paul Hirom, for the opportunity and resources to carry out the work described in this thesis. I am also very grateful towards Dr. Kevin Ghipman and Dr. Peter Millburn for their encouragement and helpful discussions of my work, and Mr. Graham Frost for his expert technical assistance at the bench, and, in the initial stages, his animal surgery. I must also thank the Medical Research Council and ICI Scholarship Trust for providing me with a grant and finance for my research. I would also like to thank Prof. Sten Orrenius of the Karolinska Institute, Stockholm, Sweden, who allowed me a short stay in his department to learn the cell isolation techniques, described in Chapter 6, in the laboratory of Dr. Kari Ormstad. Drs. Frank Cottee and Brian Reagan of Shell Research Centre, Sitting- bourne, U.K. taught me all I know on FAB and NMR mass spectrometry and I am grateful for their time and effort spent in the analyses of my samples. I would like to express my many thanks to Alison Stokes and Gill Richardson-Jones for making sense of my writing and grammar and for the typing and retyping of this manuscript. I must also thank Hester Hawkins at Smith, Kline & French for her help with the illustrations and reprographics. Finally, I would like to thank my parents for their support and encourage- ment over the years of my training and education, and my fiancee, Karen, without whose patience and understanding this work would not have been possible. To these three special people, I dedicate this thesis. - 5 - ABBREVIATIONS ATP - adenosine 5-triphosphate BSP - bromsulphthalein BSP-GSH - S-glutathione conjugate of bromsulphthalein CYS, Cys - cysteine CYSGLY - cysteinylglycine DDT - 2,2-di(£-chlorophenyl)-1,1,1-trichloroethane DNP - 2,4-dinitrophenyl EDTA - ethylenediaminetetraacetic acid EGTA - ethyleneglycol-bis-(3-aminoethyl ether)-N,N,NT,N*-tetra- acetic acid EI - electron impact FAB - fast atom bombardment Y-GCNA - y-glutamylcarboxynitroanilide GSH - reduced glutathione GSSG - oxidised glutathione Hepes - N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid h.p.l.c. - high performance liquid chromatography i.d. - intraduodenal i.p. - intraperitoneal i.v. - intravenous MA - mercapturic acid NADH - reduced nicotinamide-adenine dinucleotide NADPH - reduced nicotinamide-adenine dinucleotide phosphate NMR - nuclear magnetic resonance p.c. - paper chromatography S.D. - standard deviation t.l.c. - thin-layer chromatography Tris - tris(hydroxymethyl)aminomethane ENZYME NOMENCLATURE Enzyme names and classification numbers are used as recommended by the Nomenclature Committee of the IUB on the Nomenclature and Classi- fication of Enzymes (1978), Enzyme Nomenclature, Academic Press, N.Y. Cystathionase - EC 4»4*1»1 Cysteine conjugate B-lyase - EC 4«4»1.13 Leucine aminopeptidase - EC 3•4•11•1 - 6 - Glucose-6-phosphate dehydrogenase - EC 1.1.1.49 Y-Glutamyltransferase - EC 2.3.2.2 Glutathione peroxidase - EC 1.11.1.9 Glutathione S-transferase - EC 2.5.1.18 - 7 - The work and results reported in this thesis were carried out in the Department of Biochemistry, St. Mary's Hospital Medical School, London, U.K. between October, 1979 and March, 1983. MARTIN A. PUE - 8 - CHAPTER ONE INTRODUCTION CONTENTS Page No. LIST OF TABLES 11 LIST OF FIGURES 12 1.1 Introduction - Glutathione 13 1.2 Historical aspects 15 1.2 ii Localisation and levels 16 1.2 iii Structure 18 1.2 iv Functions 21 1.2 v Protective role of glutathione 22 1.2 vi Activation by reaction with glutathione 26 1.2 vi (a) Xenobiotic activation 26 1.2 vi (b) Endogenous compound 29 activation 1.3 i Mercapturic acid formation 29 1.3 ii Premercapturic acids 31 1.4 Enzymology of the mercapturic acid pathway 33 1.4 i Glutathione S-transferases 35 1.4 i (a) Nature of glutathione 36 S-transferases 1.4 i (b) Mode of action 41 1.4 i (c) Cellular localisation 42 1.4 i (d) Tissue distribution 43 1.4 i (e) Substrates of glutathione 45 S-transferases 1.4 i (f) Ligandin 47 1.4 i (g) Importance of ligand 50 binding by the transferases - 9 - Contents (contd.) Page No. 1.4 ii Y-Glutamyltransferase 52 1.4 iii Aminopeptidases 56 1.4 iv N-Acetyltransferase 57 1.5 Metabolic degradation of mercapturic acids 58 1.5 i Deacetylation 59 1.5 ii Cysteine conjugate 6-lyase 60 1.5 iii S-Oxidation 64 1.6 Excretion of conjugated xenobiotics 65 1.7 Biliary excretion 65 1.7 i Biliary excretion of glutathione 68 conjugates 1.8 Intestinal metabolism of conjugates of xenobiotics 73 1.8 i Bacterial metabolism 73 1.8 i (a) Hydrolysis of glucuronides 74 by intestinal microflora 1.8 i (b) Metabolism of glutathione 75 conjugates by intestinal microflora 1.8 ii Intestinal tissue metabolism 76 1.8 ii (a) Hydrolysis of glucuronides 77 by intestinal tissue 1.8 ii (b) Metabolism of glutathione 78 conjugates by intestinal tissue 1.9 i Enterohepatic circulation of 3-glu- 79 curonic acid conjugates 1.9 ii Enterohepatic circulation of glutathione 81 S-conjugates 1.10 Purpose of the study 83 - 10 - CHAPTER ONE LIST OF TABLES Page No. Table 1.1 Levels of reduced glutathione (GSH) 17 in liver and some extrahepatic tissues of rat and rabbit Table 1.2 Functions of glutathione 23 Table 1.3 Classifications used for the nomencla- 4.0 ture of the basic glutathione S-trans- ferases of rat liver cytosol Table 1.4- Glutathione S-transferase activity 4-4- towards styrene oxide in several tissues of rat and rabbit Table 1.5 Compounds which bind to the glutathione 4-9 S-transferases (ligandins) as non- substrates Table 1.6 Distribution of Y-glutamyltransferase 53 in rat tissues Table 1.7 Substrate specificity of cysteine con- 62 jugate 3-lyase from rat liver cytosol Table 1.8 Examples of compounds excreted in bile 69 as glutathione conjugates Table 1.9 Examples of compounds which undergo 80 enterohepatic circulation following biliary excretion as 6-glucuronides in the rat - 11 - CHAPTER ONE LIST OF FIGURES Page No. Figure 1.1 Structure of glutathione . 19 Figure 1.2 Mercapturic acid pathway 34 - 12 - 1.1 Introduction - Glutathione Chemical compounds entering the organism which are unable to be utilised as a food source by that organism are termed foreign compounds or xenobiotics. Such xenobiotics may include drugs, naturally occurring compounds, environmental contaminants or metals. The majority of these compounds are metabolised and transformed into other substances by processes within the organism. The metabolic conversions such xenobio- tics undergo are referred to as detoxication mechanisms and are now reasonably well understood (Williams, 1959; Parke, 1968).
Load more

Recommended publications
  • Table of Contents
    Table of contents SUMMARY IX ZUSAMMENFASSUNG XI 1. INTRODUCTION 1 1.1 The immune system 1 1.1.1 Function 1 1.1.2 Overview 1 1.1.3 Function of MHC molecules 1 1.1.4 The Major Histocompatibility Complex (MHC) Genes 2 1.1.5 Structure of MHC molecules 2 1.2 Antigen presentation 5 1.2.1 Outline of the conventional MHC class I pathway 5 1.3 The components of the peptide loading complex 7 1.3.1 Transporter associated with antigen presentation (TAP) 7 1.3.2 Calreticulin and calnexin 9 1.3.4 ERp 57/ER60 10 1.3.5 Tapasin (Tpn) 11 1.4 (a) The proteasomes 12 1.4 (b) Cytosolic peptidase 15 1.5 Endoplasmic Reticulum Associated Peptidase/s 16 1.6 Protein sorting 17 1.6.2 Vesicular transport in the Golgi apparatus 20 1.6.3 Endocytic pathway 20 1.6.4 Endocytic proteases 24 1.6.4.1 Biosynthesis and transport of cathepsins 25 1.6.4.2 Activation of cathepsins 26 1.6.4.3 Inhibitors of endosomal proteases. 26 1.7 Antigen processing by alternative pathways 27 1.8 Aim of the thesis 30 i 2. MATERIALS AND METHODS 31 2.1 Materials 31 2.1.1 Bacterial strains 31 2.1.2 Plasmids 31 2.1.2.1 Construction of plasmids 31 2.1.3 Primer list 32 2.1.4 PCR conditions 33 2.1.5 Antibiotics 34 2.1.6 Chemicals 34 2.1.7 Media for bacterial cells 34 2.1.8 Protein Chemicals 35 2.1.9 Animal cell culture media 37 2.1.11 Antibodies 39 2.1.11 siRNA oligonucleotides.
    [Show full text]
  • Serine Proteases with Altered Sensitivity to Activity-Modulating
    (19) & (11) EP 2 045 321 A2 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.: 08.04.2009 Bulletin 2009/15 C12N 9/00 (2006.01) C12N 15/00 (2006.01) C12Q 1/37 (2006.01) (21) Application number: 09150549.5 (22) Date of filing: 26.05.2006 (84) Designated Contracting States: • Haupts, Ulrich AT BE BG CH CY CZ DE DK EE ES FI FR GB GR 51519 Odenthal (DE) HU IE IS IT LI LT LU LV MC NL PL PT RO SE SI • Coco, Wayne SK TR 50737 Köln (DE) •Tebbe, Jan (30) Priority: 27.05.2005 EP 05104543 50733 Köln (DE) • Votsmeier, Christian (62) Document number(s) of the earlier application(s) in 50259 Pulheim (DE) accordance with Art. 76 EPC: • Scheidig, Andreas 06763303.2 / 1 883 696 50823 Köln (DE) (71) Applicant: Direvo Biotech AG (74) Representative: von Kreisler Selting Werner 50829 Köln (DE) Patentanwälte P.O. Box 10 22 41 (72) Inventors: 50462 Köln (DE) • Koltermann, André 82057 Icking (DE) Remarks: • Kettling, Ulrich This application was filed on 14-01-2009 as a 81477 München (DE) divisional application to the application mentioned under INID code 62. (54) Serine proteases with altered sensitivity to activity-modulating substances (57) The present invention provides variants of ser- screening of the library in the presence of one or several ine proteases of the S1 class with altered sensitivity to activity-modulating substances, selection of variants with one or more activity-modulating substances. A method altered sensitivity to one or several activity-modulating for the generation of such proteases is disclosed, com- substances and isolation of those polynucleotide se- prising the provision of a protease library encoding poly- quences that encode for the selected variants.
    [Show full text]
  • 03-232 Biochemistry Exam II – 2012 -Key Name:______Instructions: This Exam Consists of 100 Points on 6 Pages
    03-232 Biochemistry Exam II – 2012 -Key Name:________________________ Instructions: This exam consists of 100 points on 6 pages. Please use the space provided to answer the question or the back of the preceding page. In questions with choices, all your answers will be graded and you will receive the best grade. Allot 1 min/2 points. A B 1. (10 pts) One protein (protein A) binds naphthalene (ligand) by sandwiching it between two tryptophan residues. Another protein Trp L Trp Tyr L Tyr (protein B) also binds naphthalene by sandwiching it between two OH tyrosine residues, however the binding is weaker. The structure of the H protein-ligand complex is shown on the right (side view), the structures N of tryptophan, naphthalene (ligand), and tyrosine are shown as well. i) What are the principal energetic factor(s) that are responsible for binding of naphthalene to these proteins? (4 pts) Tryptophan(Trp) naphthalene (L) Tyrosine (Tyr) ii) Why does the tyrosine containing protein show weaker binding? (4 pts) ii) Which kinetic rate constant, the off-rate (kOFF) or the on-rate (kON), would be most different between the two proteins? In what way would it differ? Why? (2 pts) i) van der waals (H) and the hydrophobic effect (S) (3 pts for one, 4 points for two). ii) van der waals is reduce because the contact between the tyrosine and the ligand will be smaller. There will be a smaller hydrophobic effect as well because the non-polar surface area of tyrosine is smaller than tryptophan. Therefore in protein B, a smaller number of ordered water molecules will be released.
    [Show full text]
  • Discovery of Oxidative Enzymes for Food Engineering. Tyrosinase and Sulfhydryl Oxi- Dase
    Dissertation VTT PUBLICATIONS 763 1,0 0,5 Activity 0,0 2 4 6 8 10 pH Greta Faccio Discovery of oxidative enzymes for food engineering Tyrosinase and sulfhydryl oxidase VTT PUBLICATIONS 763 Discovery of oxidative enzymes for food engineering Tyrosinase and sulfhydryl oxidase Greta Faccio Faculty of Biological and Environmental Sciences Department of Biosciences – Division of Genetics ACADEMIC DISSERTATION University of Helsinki Helsinki, Finland To be presented for public examination with the permission of the Faculty of Biological and Environmental Sciences of the University of Helsinki in Auditorium XII at the University of Helsinki, Main Building, Fabianinkatu 33, on the 31st of May 2011 at 12 o’clock noon. ISBN 978-951-38-7736-1 (soft back ed.) ISSN 1235-0621 (soft back ed.) ISBN 978-951-38-7737-8 (URL: http://www.vtt.fi/publications/index.jsp) ISSN 1455-0849 (URL: http://www.vtt.fi/publications/index.jsp) Copyright © VTT 2011 JULKAISIJA – UTGIVARE – PUBLISHER VTT, Vuorimiehentie 5, PL 1000, 02044 VTT puh. vaihde 020 722 111, faksi 020 722 4374 VTT, Bergsmansvägen 5, PB 1000, 02044 VTT tel. växel 020 722 111, fax 020 722 4374 VTT Technical Research Centre of Finland, Vuorimiehentie 5, P.O. Box 1000, FI-02044 VTT, Finland phone internat. +358 20 722 111, fax + 358 20 722 4374 Edita Prima Oy, Helsinki 2011 2 Greta Faccio. Discovery of oxidative enzymes for food engineering. Tyrosinase and sulfhydryl oxi- dase. Espoo 2011. VTT Publications 763. 101 p. + app. 67 p. Keywords genome mining, heterologous expression, Trichoderma reesei, Aspergillus oryzae, sulfhydryl oxidase, tyrosinase, catechol oxidase, wheat dough, ascorbic acid Abstract Enzymes offer many advantages in industrial processes, such as high specificity, mild treatment conditions and low energy requirements.
    [Show full text]
  • Nano-Evolution and Protein-Based Enzymatic Evolution Predicts the Novel
    View Article Online View Journal Nanoscale Advances Accepted Manuscript This article can be cited before page numbers have been issued, to do this please use: G. Nazarbek, A. Kutzhanova, L. Nurtay , C. Mu, B. Kazybay, X. Li, C. Ma, A. Amin and Y. Xie, Nanoscale Adv., 2021, DOI: 10.1039/D1NA00475A. Volume 1 Number 1 This is an Accepted Manuscript, which has been through the January 2018 Pages 1-200 Royal Society of Chemistry peer review process and has been accepted Nanoscale for publication. Advances Accepted Manuscripts are published online shortly after acceptance, rsc.li/nanoscale-advances before technical editing, formatting and proof reading. Using this free service, authors can make their results available to the community, in citable form, before we publish the edited article. We will replace this Accepted Manuscript with the edited and formatted Advance Article as soon as it is available. You can find more information about Accepted Manuscripts in the Information for Authors. Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal’s standard ISSN 2516-0230 Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains. rsc.li/nanoscale-advances Page 1 of 25 Nanoscale Advances 1 Nano-evolution and protein-based enzymatic evolution predicts the novel View Article Online
    [Show full text]
  • This Exam Contains 8 Pages and Consists of 90 Points
    Biochemistry I Exam 2 – 2007 Name:_____________________________ This exam contains 8 pages and consists of 90 points. Allot 2 pts/min. 1. (15 pts) Provide a brief and general description of allosteric effects in biochemical systems (10 pts). Your answer should clearly define tense and relaxed states as well as homotropic and heterotropic compounds. Use either oxygen transport to the tissues or the adaptation of oxygen transport at high altitudes to illustrate your answer (5 pts). 1. ____________/15 2. ____________/12 3. ____________/ 8 4. ____________/12 5. ____________/ 5 6. ____________/10 7. ____________/10 8. ____________/18 Total___________/90 1 Biochemistry I Exam 2 – 2007 Name:_____________________________ 2. (12 pts) Please answer one of the following three choices. Please indicate your choice Choice A: Briefly describe in general terms, using the framework of transition state theory, how enzymes increase the rate of reactions. Choice B: Most proteins (enzymes) are highly specific for their ligands (substrates). Briefly discuss why this is the case and illustrate your answer using any protein or enzyme that we have discussed in the course so far. Choice C: Most enzymes utilize specific residues to accomplish chemical catalysis. Discuss the role of such residues in either the mechanism of serine proteases or HIV protease. 3. (8 pts) Please do one of the following two choices. Choice A: Enzyme kinetic measurements are usually performed under conditions of “steady-state”. Briefly describe what “steady-state” means. Choice B: In enzyme kinetic measurements it is customary to measure the initial rate of the reaction. Why is this important? 2 Biochemistry I Exam 2 – 2007 Name:_____________________________ 4.
    [Show full text]
  • Systematic Evaluation of Genetic Variants for Polycystic Ovary Syndrome in a Chinese Population
    RESEARCH ARTICLE Systematic Evaluation of Genetic Variants for Polycystic Ovary Syndrome in a Chinese Population Yuping Xu1,2,3, Zhiqiang Li4, Fenglian Ai1,2,3, Jianhua Chen4, Qiong Xing1,2,3, Ping Zhou1,2,3, Zhaolian Wei1,2,3, Yongyong Shi4*, Xiao-Jin He1,2,3*, Yunxia Cao1,2,3* 1 Reproductive Medicine Center, Department of Obstetrics and Gynecology, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022, China, 2 Institute of Reproductive Genetics, Anhui Medical University, Hefei, 230022, China, 3 Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs, Hefei, 230022, China, 4 The Bio-X Institutes, Shanghai Jiao Tong University, 1954 Huashan Road, Shanghai, 200030, China * [email protected] (YC); [email protected] (YS); [email protected] (XH) Abstract − To date, eleven genome-wide significant (GWS) loci (P < 5×10 8) for polycystic ovary syn- OPEN ACCESS drome (PCOS) have been identified through genome-wide association studies (GWAS). Citation: Xu Y, Li Z, Ai F, Chen J, Xing Q, Zhou P, et Some of the risk loci have been selected for replications and validated in multiple ethnicities, al. (2015) Systematic Evaluation of Genetic Variants however, few previous studies investigated all loci. Scanning all the GWAS variants would for Polycystic Ovary Syndrome in a Chinese demonstrate a more informative profile of variance they explained. Thus, we analyzed all Population. PLoS ONE 10(10): e0140695. the 17 single nucleotide polymorphisms (SNPs) mapping to the 11 GWAS loci in an inde- doi:10.1371/journal.pone.0140695 pendent sample set of 800 Chinese subjects with PCOS and 1110 healthy controls system- Editor: Stephen L Atkin, Weill Cornell Medical − atically.
    [Show full text]
  • Free Radicals, Natural Antioxidants, and Their Reaction Mechanisms Cite This: RSC Adv.,2015,5, 27986 Satish Balasaheb Nimse*A and Dilipkumar Palb
    RSC Advances REVIEW View Article Online View Journal | View Issue Free radicals, natural antioxidants, and their reaction mechanisms Cite this: RSC Adv.,2015,5, 27986 Satish Balasaheb Nimse*a and Dilipkumar Palb The normal biochemical reactions in our body, increased exposure to the environment, and higher levels of dietary xenobiotic's result in the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). The ROS and RNS create oxidative stress in different pathophysiological conditions. The reported chemical evidence suggests that dietary antioxidants help in disease prevention. The antioxidant compounds react in one-electron reactions with free radicals in vivo/in vitro and prevent oxidative damage. Therefore, it is very important to understand the reaction mechanism of antioxidants with the free radicals. This review elaborates the mechanism of action of the natural antioxidant compounds and Received 28th October 2014 assays for the evaluation of their antioxidant activities. The reaction mechanisms of the antioxidant Accepted 12th March 2015 assays are briefly discussed (165 references). Practical applications: understanding the reaction DOI: 10.1039/c4ra13315c mechanisms can help in evaluating the antioxidant activity of various antioxidant compounds as well as Creative Commons Attribution 3.0 Unported Licence. www.rsc.org/advances in the development of novel antioxidants. 1. Introduction and background enzymes convert dangerous oxidative products to hydrogen peroxide (H2O2) and then to water, in a multi-step process in Antioxidants are molecules that inhibit or quench free radical presence of cofactors such as copper, zinc, manganese, and reactions and delay or inhibit cellular damage.1 Though the iron. Non-enzymatic antioxidants work by interrupting free antioxidant defenses are different from species to species, the radical chain reactions.
    [Show full text]
  • GLUTATHIONE) OXIDASE from Y-GLUTAMYLTRANSFERASE
    Volume 124, number 2 FEBS LETTERS February 1981 RESOLUTION OF A RENAL SULFHYDRYL (GLUTATHIONE) OXIDASE FROM y-GLUTAMYLTRANSFERASE Samy ASHKAR, Francis BINKLEY and Dean P. JONES Department of Biochemistry, School of Medicine, Emory University,Atlanta, GA 30322, USA Received 2 January 1981 1. Introduction with 0.9% NaCl (w/v) at O”C, decapsulated and homogenized in cold 0.08 M Tris-HCl (pH 7.6) con- Rapid oxidation of GSH by kidney extracts was taining 1 mM EDTA. The homogenate was centrifuged recognized by Ames and Elvehem 30 years ago [ 11, at 800 X g for 15 min. The supernatant was recentri- but further investigation of this process did not fuged at 100 000 X g for 2 h and the supernatant dis- proceed until it was recently rediscovered in studies carded. The precipitate was resuspended in 0.08 M of GSH metabolism by isolated kidney cells [2,3]. Tris-HCl (pH 7.6) containing 1% Triton X-100 (v/v) The reaction requires molecular oxygen [3] and has and 1 mM DTT, and allowed to stand overnight at the stoichiometry: 4°C. Samples (1 ml) were applied to a descending gel filtration column (Bio-Rad P-200, 1.5 X 35 cm) pre- 2GSH+02 + GSSG + H,Oz [4] equilibrated with 0.08 M Tris-HCl (pH 7.6) contain- ing 30% glycerol (v/v) at room temperature and eluted The reaction was shown to be insensitive to inhibi- with the same buffer; active fractions were pooled. tion by 20 mM serine-borate [3], a complex that Sulfhydryl oxidation was measured as disappear- gives essentially complete inhibition of y-glutamyl ance of free sulfhydryl according to (93 as modified transferase (?-CT) [5].
    [Show full text]
  • Characterization of Cytosolic Glutathione Peroxidase And
    Aquatic Toxicology 130–131 (2013) 97–111 Contents lists available at SciVerse ScienceDirect Aquatic Toxicology jou rnal homepage: www.elsevier.com/locate/aquatox Characterization of cytosolic glutathione peroxidase and phospholipid-hydroperoxide glutathione peroxidase genes in rainbow trout (Oncorhynchus mykiss) and their modulation by in vitro selenium exposure a a b a d c a,∗ D. Pacitti , T. Wang , M.M. Page , S.A.M. Martin , J. Sweetman , J. Feldmann , C.J. Secombes a Scottish Fish Immunology Research Centre, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, United Kingdom b Integrative and Environmental Physiology, Institute of Biological and Environmental Sciences, University of Aberdeen, Aberdeen AB24 2TZ, United Kingdom c Trace Element Speciation Laboratory, Department of Chemistry, University of Aberdeen, Aberdeen AB24 3UE, United Kingdom d Alltech Biosciences Centre, Sarney, Summerhill Rd, Dunboyne, Country Meath, Ireland a r t i c l e i n f o a b s t r a c t Article history: Selenium (Se) is an oligonutrient with both essential biological functions and recognized harmful effects. Received 4 July 2012 As the selenocysteine (SeCys) amino acid, selenium is integrated in several Se-containing proteins Received in revised form (selenoproteins), many of which are fundamental for cell homeostasis. Nevertheless, selenium may exert 19 December 2012 toxic effects at levels marginally above those required, mainly through the generation of reactive oxygen Accepted 20 December 2012 species (ROS). The selenium chemical speciation can strongly affect the bioavailability of this metal and its impact on metabolism, dictating the levels that can be beneficial or detrimental towards an organism.
    [Show full text]
  • Vitamin C and Human Health
    Vitamin C and Human Health Edited by Anitra C. Carr and Margreet M.C. Vissers Printed Edition of the Special Issue Published in Nutrients www.mdpi.com/journal/nutrients Anitra C. Carr and Margreet M.C. Vissers (Eds.) Vitamin C and Human Health This book is a reprint of the special issue that appeared in the online open access journal Nutrients (ISSN 2072-6643) in 2013 (available at: http://www.mdpi.com/journal/nutrients/special_issues/vitamin_C_and_human_health). Guest Editors Anitra C. Carr Research Fellow & Centre Co-ordinator, Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch 8140, New Zealand Margreet C. M. Vissers Professor & Associate Dean (Research), Centre for Free Radical Research, Department of Pathology, University of Otago Christchurch 8140, New Zealand Editorial Office MDPI AG Klybeckstrasse 64 Basel, Switzerland Publisher Shu-Kun Lin Production Editor Martyn Rittman 1. Edition 2014 MDPI • Basel • Beijing ISBN 978-3-906980-62-1 © 2014 by the authors; licensee MDPI, Basel, Switzerland. All articles in this volume are Open Access distributed under the Creative Commons Attribution 3.0 license (http://creativecommons.org/licenses/by/3.0/), which allows users to download, copy and build upon published articles even for commercial purposes, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications. However, the dissemination and distribution of copies of this book as a whole is restricted to MDPI, Basel, Switzerland. III Table of Contents Anitra C. Carr and Margreet M.C. Vissers Preface Guest Editors ................................................................................................................ V 1. Methodology Overview Alexander J.
    [Show full text]
  • Riboflavin: the Health Benefits of a Forgotten Natural Vitamin
    International Journal of Molecular Sciences Review Riboflavin: The Health Benefits of a Forgotten Natural Vitamin Nittiya Suwannasom 1,2 , Ijad Kao 1 , Axel Pruß 1, Radostina Georgieva 1,3 and Hans Bäumler 1,* 1 Institute of Transfusion Medicine, Center of Tumor Medicine, Charité—Universitätsmedizin Berlin, Charitéplatz 1, 10117 Berlin, Germany; [email protected] (N.S.); [email protected] (I.K.); [email protected] (A.P.); [email protected] (R.G.) 2 School of Medical Sciences, University of Phayao, Phayao 56000, Thailand 3 Biophysics and Radiology, Department of Medical Physics, Faculty of Medicine, Trakia University, 6000 Stara Zagora, Bulgaria * Correspondence: [email protected] Received: 3 January 2020; Accepted: 29 January 2020; Published: 31 January 2020 Abstract: Riboflavin (RF) is a water-soluble member of the B-vitamin family. Sufficient dietary and supplemental RF intake appears to have a protective effect on various medical conditions such as sepsis, ischemia etc., while it also contributes to the reduction in the risk of some forms of cancer in humans. These biological effects of RF have been widely studied for their anti-oxidant, anti-aging, anti-inflammatory, anti-nociceptive and anti-cancer properties. Moreover, the combination of RF and other compounds or drugs can have a wide variety of effects and protective properties, and diminish the toxic effect of drugs in several treatments. Research has been done in order to review the latest findings about the link between RF and different clinical aberrations. Since further studies have been published in this field, it is appropriate to consider a re-evaluation of the importance of RF in terms of its beneficial properties.
    [Show full text]