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Arnhold J, Malle E. Halogenation Activity of Mammalian Heme Peroxidases. Antioxidants (Basel) 2022; 11:antiox11050890. [PMID: 35624754 PMCID: PMC9138014 DOI: 10.3390/antiox11050890] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 12/10/2022] Open
Abstract
Mammalian heme peroxidases are fascinating due to their unique peculiarity of oxidizing (pseudo)halides under physiologically relevant conditions. These proteins are able either to incorporate oxidized halides into substrates adjacent to the active site or to generate different oxidized (pseudo)halogenated species, which can take part in multiple (pseudo)halogenation and oxidation reactions with cell and tissue constituents. The present article reviews basic biochemical and redox mechanisms of (pseudo)halogenation activity as well as the physiological role of heme peroxidases. Thyroid peroxidase and peroxidasin are key enzymes for thyroid hormone synthesis and the formation of functional cross-links in collagen IV during basement membrane formation. Special attention is directed to the properties, enzymatic mechanisms, and resulting (pseudo)halogenated products of the immunologically relevant proteins such as myeloperoxidase, eosinophil peroxidase, and lactoperoxidase. The potential role of the (pseudo)halogenated products (hypochlorous acid, hypobromous acid, hypothiocyanite, and cyanate) of these three heme peroxidases is further discussed.
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Affiliation(s)
- Jürgen Arnhold
- Medical Faculty, Institute of Medical Physics and Biophysics, Leipzig University, 04107 Leipzig, Germany
- Correspondence: (J.A.); or (E.M.)
| | - Ernst Malle
- Gottfried Schatz Research Center, Division of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
- Correspondence: (J.A.); or (E.M.)
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Tonoyan L, Montagner D, Friel R, O'Flaherty V. Antimicrobials offered from nature: Peroxidase-catalyzed systems and their mimics. Biochem Pharmacol 2020; 182:114281. [PMID: 33075313 DOI: 10.1016/j.bcp.2020.114281] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/07/2020] [Accepted: 10/08/2020] [Indexed: 10/23/2022]
Abstract
The control of antimicrobial resistance requires the development of novel antimicrobial alternatives and naturally occurring peroxidase-catalyzed systems may be of great value in this era of emerging antimicrobial resistance. In the peroxidase system, a peroxidase enzyme catalyzes the oxidation of a halide/pseudohalide, at the expense of hydrogen peroxide, to generate reactive products with broad antimicrobial properties. The appropriate use of peroxidase systems needs a better understanding of the identities and properties of the generated antimicrobial oxidants, specific targets in bacterial cells, their mode of action and the factors favoring or limiting their activity. Here, the ABCs (antibacterial activity, bacterial "backtalk" and cytotoxicity) of these systems and their mimics are discussed. Particular attention is paid to the concomitant use of thiocyanate and iodide dual substrates in peroxidase/peroxidase-free systems with implications on their antimicrobial activity. This review also provides a summary of actual applications of peroxidase systems as bio-preservatives in oral healthcare, milk industry, food/feed specialties and related products, mastitis and wound treatment; lastly, this review points to opportunities for further research and potential applications.
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Affiliation(s)
- Lilit Tonoyan
- Department of Microbiology, School of Natural Sciences and Ryan Institute, National University of Ireland Galway, Galway, Ireland.
| | - Diego Montagner
- Department of Chemistry, Maynooth University, Maynooth, Ireland; Kathleen Lonsdale Institute for Human Health Research, Maynooth University, Maynooth, Ireland
| | - Ruairi Friel
- Westway Health, Unit 120, Business Innovation Centre, National University of Ireland Galway, Galway, Ireland
| | - Vincent O'Flaherty
- Department of Microbiology, School of Natural Sciences and Ryan Institute, National University of Ireland Galway, Galway, Ireland.
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3
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Mediavilla JJV, Perez BF, Cordoba MCFD, Espina JA, Ania CO. Photochemical Degradation of Cyanides and Thiocyanates from an Industrial Wastewater. Molecules 2019; 24:molecules24071373. [PMID: 30965653 PMCID: PMC6480199 DOI: 10.3390/molecules24071373] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/05/2019] [Accepted: 04/06/2019] [Indexed: 11/16/2022] Open
Abstract
We have explored the simultaneous degradation of cyanides and thiocyanate present in wastewaters from a cokemaking factory using photoassisted methods under varied illumination conditions (from simulated solar light to UV light). Overall, the photochemical degradation of cyanides was more efficient than that of thiocyanates, regardless of the illumination conditions, the effect being more pronounced in the absence of a photocatalyst. This is due to their different degradation mechanism that in the case of thiocyanates is dominated by fast recombination reactions and/or charge transfer reactions to electron scavengers. In all cases, cyanate, ammonia, nitrates, and nitrites were formed at different amounts depending on the illumination conditions. The conversion yield under simulated solar light was almost complete for cyanides and quite high for thiocyanates after 6 h of illumination. Regarding toxicity, photochemical oxidation at 254 nm and under simulated solar light decreased significantly the toxicity of the pristine wastewater, showing a correlation with the intensity of the irradiation source. This indicate that simulated light can be effectively used to reduce the toxicity of industrial effluents, opening an interesting perspective for optimizing cyanide detoxification systems based on natural light.
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Affiliation(s)
| | - Begoña Fernandez Perez
- Escuela Técnica Superior de Ingeniería de Minas, Universidad de Oviedo, 33001 Oviedo, Spain.
| | | | - Julia Ayala Espina
- Escuela Técnica Superior de Ingeniería de Minas, Universidad de Oviedo, 33001 Oviedo, Spain.
| | - Conchi O Ania
- CEMHTI, CNRS (UPR 3079), Université d'Orléans, 45071 Orléans, France.
- Instituto Nacional del Carbón (INCAR, CSIC), Apdo. 73, 33080 Oviedo, Spain.
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Eiserich JP, Ott SP, Kadir T, Morrissey BM, Hayakawa KA, La Merrill MA, Cross CE. Quantitative assessment of cyanide in cystic fibrosis sputum and its oxidative catabolism by hypochlorous acid. Free Radic Biol Med 2018; 129:146-154. [PMID: 30213640 DOI: 10.1016/j.freeradbiomed.2018.09.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 09/07/2018] [Indexed: 02/06/2023]
Abstract
RATIONALE Cystic fibrosis (CF) patients are known to produce cyanide (CN-) although challenges exist in determinations of total levels, the precise bioactive levels, and specificity of its production by CF microflora, especially P. aeruginosa. Our objective was to measure total CN- levels in CF sputa by a simple and novel technique in P. aeruginosa positive and negative adult patients, to review respiratory tract (RT) mechanisms for the production and degradation of CN-, and to interrogate sputa for post-translational protein modification by CN- metabolites. METHODS Sputa CN- concentrations were determined by using a commercially available CN- electrode, measuring levels before and after addition of cobinamide, a compound with extremely high affinity for CN-. Detection of protein carbamoylation was measured by Western blot. MEASUREMENTS AND MAIN RESULTS The commercial CN- electrode was found to overestimate CN- levels in CF sputum in a highly variable manner; cobinamide addition rectified this analytical issue. Although P. aeruginosa positive patients tended to have higher total CN- values, no significant differences in CN- levels were found between positive and negative sputa. The inflammatory oxidant hypochlorous acid (HOCl) was shown to rapidly decompose CN-, forming cyanogen chloride (CNCl) and the carbamoylating species cyanate (NCO-). Carbamoylated proteins were found in CF sputa, analogous to reported findings in asthma. CONCLUSIONS Our studies indicate that CN- is a transient species in the inflamed CF airway due to multiple biosynthetic and metabolic processes. Stable metabolites of CN-, such as cyanate, or carbamoylated proteins, may be suitable biomarkers of overall CN- production in CF airways.
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Affiliation(s)
- Jason P Eiserich
- Department of Internal Medicine, Division of Pulmonary/Critical Care and Sleep Medicine, University of California, Davis, CA 95616, United States; Department of Physiology and Membrane Biology, University of California, Davis, CA 95616, United States
| | - Sean P Ott
- Department of Internal Medicine, Division of Pulmonary/Critical Care and Sleep Medicine, University of California, Davis, CA 95616, United States
| | - Tamara Kadir
- Department of Internal Medicine, Division of Pulmonary/Critical Care and Sleep Medicine, University of California, Davis, CA 95616, United States
| | - Brian M Morrissey
- Department of Internal Medicine, Division of Pulmonary/Critical Care and Sleep Medicine, University of California, Davis, CA 95616, United States
| | - Keri A Hayakawa
- Department of Internal Medicine, Division of Pulmonary/Critical Care and Sleep Medicine, University of California, Davis, CA 95616, United States
| | - Michele A La Merrill
- Department of Environmental Toxicology, University of California, Davis, CA 95616, United States
| | - Carroll E Cross
- Department of Internal Medicine, Division of Pulmonary/Critical Care and Sleep Medicine, University of California, Davis, CA 95616, United States; Department of Physiology and Membrane Biology, University of California, Davis, CA 95616, United States.
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5
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New insights into thiocyanate oxidation by human myeloperoxidase. J Inorg Biochem 2016; 162:117-126. [PMID: 27343172 DOI: 10.1016/j.jinorgbio.2016.06.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 05/26/2016] [Accepted: 06/14/2016] [Indexed: 11/20/2022]
Abstract
Human myeloperoxidase (MPO) uses chloride and thiocyanate as physiological substrates at neutral pH. Oxidation of thiocyanate to hypothiocyanite mediated by the redox intermediate Compound I rapidly restores the ferric state of MPO. At low thiocyanate concentration and in the presence of hydrogen peroxide the observed reaction sequence is Compound I→ferric MPO→Compound II→MPO-cyanide complex, whereas at high thiocyanate concentrations and in the absence of H2O2 the only observed transition is Compound I→ferric MPO. The reaction of ferric MPO with hypothiocyanite directly forms the MPO-cyanide complex, whereas a transient product derived from the reaction between hypothiocyanite and hydrogen peroxide is demonstrated to mediate the conversion of ferric MPO to Compound II. Mechanisms for those reactions are discussed and proposed.
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Flemmig J, Gau J, Schlorke D, Arnhold J. Lactoperoxidase as a potential drug target. Expert Opin Ther Targets 2015; 20:447-61. [DOI: 10.1517/14728222.2016.1112378] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jörg Flemmig
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstraße 16 – 18, 04107 Leipzig, Germany
- Translational Centre for Regenerative Medicine (TRM) Leipzig, University of Leipzig, Leipzig, Germany
| | - Jana Gau
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstraße 16 – 18, 04107 Leipzig, Germany
| | - Denise Schlorke
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstraße 16 – 18, 04107 Leipzig, Germany
- Translational Centre for Regenerative Medicine (TRM) Leipzig, University of Leipzig, Leipzig, Germany
| | - Jürgen Arnhold
- Institute for Medical Physics and Biophysics, Medical Faculty, University of Leipzig, Härtelstraße 16 – 18, 04107 Leipzig, Germany
- Translational Centre for Regenerative Medicine (TRM) Leipzig, University of Leipzig, Leipzig, Germany
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7
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The Role of Posttranslational Protein Modifications in Rheumatological Diseases: Focus on Rheumatoid Arthritis. J Immunol Res 2015; 2015:712490. [PMID: 26090496 PMCID: PMC4451265 DOI: 10.1155/2015/712490] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Revised: 01/16/2015] [Accepted: 02/05/2015] [Indexed: 01/12/2023] Open
Abstract
The definition of posttranslational modification (PTM) encompasses a wide group of chemical reactions that allow modification and modulation of protein functions. The regulation of PTMs is crucial for the activity and survival of the cells. Dysregulation of PTMs has been observed in several pathological conditions, including rheumatoid arthritis (RA). RA is a systemic autoimmune disease primarily targeting the joints. The three PTMs mainly involved in this disease are glycosylation, citrullination, and carbamylation. Glycosylation is essential for antigen processing and presentation and can modulate immunoglobulin activity. Citrullination of self-antigens is strongly associated with RA, as demonstrated by the presence of antibodies directed to anti-citrullinated proteins in patients' sera. Carbamylation and its dysregulation have been recently associated with RA. Aim of this review is to illustrate the most significant alterations of these PTMs in RA and to evaluate their possible involvement in the pathogenesis of the disease.
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Whitehouse M, Butters D, Vernon-Roberts B. Conditional pharmacology/toxicology V: ambivalent effects of thiocyanate upon the development and the inhibition of experimental arthritis in rats by aurothiomalate (Myocrysin®) and metallic silver. Inflammopharmacology 2013; 21:291-300. [PMID: 23686086 DOI: 10.1007/s10787-013-0173-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/26/2013] [Indexed: 10/26/2022]
Abstract
This article discusses the bizarre and contrary effects of thiocyanate, the major detoxication product of hydrogen cyanide inhaled from tobacco smoke or liberated from cyanogenic foods, e.g. cassava. Thiocyanate both (1) promotes inflammatory disease in rats and (2) facilitates the anti-inflammatory action of historic metal therapies based on gold (Au) or silver (Ag) in three models of chronic polyarthritis in rats. Low doses of nanoparticulate metallic silver (NMS) preparations, i.e. zerovalent silver (Ag°) administered orally, suppressed the mycobacterial ('adjuvant')-induced arthritis (MIA) in rats. Similar doses of cationic silver, Ag(I), administered orally as silver oxide or soluble silver salts were inactive. By contrast, NMS only inhibited the development of the collagen-induced arthritis (CIA) and pristane-induced arthritis (PIA) in rats when thiocyanate was also co-administered in drinking water. These (a) arthritis-selective and (b) thiocyanate-inducible effects of Ag° were also observed in some previous, and now extended, studies with the classic anti-arthritic drug, sodium aurothiomalate (ATM, Myocrisin(®)) and its silver analogue (STM), administered subcutaneously to rats developing the same three forms of polyarthritis. In the absence of either Ag° or ATM, thiocyanate considerably increased the severity of the MIA, CIA and PIA, i.e. acting as a pro-pathogen. Hitherto, thiocyanate was considered relatively harmless. This may not be true in rats/people with immuno-inflammatory stress and concomitant leukocyte activation. Collectively, these findings show how the drug action of a xenobiotic might be determined by the nature (and severity) of the experimental inflammation, as an example of conditional pharmacology. They also suggest that an incipient toxicity, even of normobiotics such as thiocyanate, might likewise be modulated beneficially by well-chosen xenobiotics (drugs, nutritional supplements, etc.), i.e. conditional toxicology (Powanda 1995). Thus, both the disease and the environment may determine (1) the therapeutic action and/or (2) adverse effect(s) of xenobiotics--and even some normobiotics.
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Affiliation(s)
- Michael Whitehouse
- Discipline of Pathology, School of Medicine, University of Adelaide, Adelaide, SA 5005, Australia.
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10
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Souza CEA, Maitra D, Saed GM, Diamond MP, Moura AA, Pennathur S, Abu-Soud HM. Hypochlorous acid-induced heme degradation from lactoperoxidase as a novel mechanism of free iron release and tissue injury in inflammatory diseases. PLoS One 2011; 6:e27641. [PMID: 22132121 PMCID: PMC3222650 DOI: 10.1371/journal.pone.0027641] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2011] [Accepted: 10/21/2011] [Indexed: 12/02/2022] Open
Abstract
Lactoperoxidase (LPO) is the major consumer of hydrogen peroxide (H2O2) in the airways through its ability to oxidize thiocyanate (SCN−) to produce hypothiocyanous acid, an antimicrobial agent. In nasal inflammatory diseases, such as cystic fibrosis, both LPO and myeloperoxidase (MPO), another mammalian peroxidase secreted by neutrophils, are known to co-localize. The aim of this study was to assess the interaction of LPO and hypochlorous acid (HOCl), the final product of MPO. Our rapid kinetic measurements revealed that HOCl binds rapidly and reversibly to LPO-Fe(III) to form the LPO-Fe(III)-OCl complex, which in turn decayed irreversibly to LPO Compound II through the formation of Compound I. The decay rate constant of Compound II decreased with increasing HOCl concentration with an inflection point at 100 µM HOCl, after which the decay rate increased. This point of inflection is the critical concentration of HOCl beyond which HOCl switches its role, from mediating destabilization of LPO Compound II to LPO heme destruction. Lactoperoxidase heme destruction was associated with protein aggregation, free iron release, and formation of a number of fluorescent heme degradation products. Similar results were obtained when LPO-Fe(II)-O2, Compound III, was exposed to HOCl. Heme destruction can be partially or completely prevented in the presence of SCN−. On the basis of the present results we concluded that a complex bi-directional relationship exists between LPO activity and HOCl levels at sites of inflammation; LPO serve as a catalytic sink for HOCl, while HOCl serves to modulate LPO catalytic activity, bioavailability, and function.
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Affiliation(s)
- Carlos Eduardo A. Souza
- Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, Michigan, United States of America
| | - Dhiman Maitra
- Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, Michigan, United States of America
| | - Ghassan M. Saed
- Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, Michigan, United States of America
| | - Michael P. Diamond
- Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, Michigan, United States of America
| | | | - Subramaniam Pennathur
- Division of Nephrology, Department of Internal Medicine, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Husam M. Abu-Soud
- Department of Obstetrics and Gynecology, The C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, Michigan, United States of America
- Department of Biochemistry and Molecular Biology, Wayne State University School of Medicine, Detroit, Michigan, United States of America
- * E-mail:
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Lemma K, Ashby MT. Reactive Sulfur Species: Kinetics and Mechanism of the Reaction of Hypothiocyanous Acid with Cyanide To Give Dicyanosulfide in Aqueous Solution. Chem Res Toxicol 2009; 22:1622-8. [DOI: 10.1021/tx900212r] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kelemu Lemma
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
| | - Michael T. Ashby
- Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019
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12
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Pro-inflammatory activity in rats of thiocyanate, a metabolite of the hydrocyanic acid inhaled from tobacco smoke. Inflamm Res 2009; 58:693-704. [DOI: 10.1007/s00011-009-0038-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2007] [Revised: 03/17/2009] [Accepted: 03/18/2009] [Indexed: 10/20/2022] Open
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Abstract
Various microorganisms can produce (cyanogenesis) or degrade cyanide. They degrade cyanide either to detoxify it, or to use it as a source of nitrogen for growth. Significant amounts of cyanide are formed as a secondary metabolite by a wide range of fungi and a few bacteria by decarboxylation of glycine. When cyanide has been formed by the snow mould fungus it is degraded by conversion to carbon dioxide and ammonia via an unknown pathway. In contrast, cyanogenic bacteria either do not further catabolize cyanide or they convert it into beta-cyanoalanine by addition to cysteine or O-acetylserine. Several non-cyanogenic fungi that are pathogens of cyanogenic plants are known to degrade cyanide by hydration to formamide by the enzyme cyanide hydratase. Such fungi can be immobilized and used in packed-cell columns to continuously detoxify cyanide. ICI Biological Products Business market a preparation of spray-dried fungal mycelia, 'CYCLEAR', to detoxify industrial wastes. Novo Industri have also introduced a cyanidase preparation to convert cyanide directly into formate and ammonia. Bacteria have been isolated that use cyanide as a source of nitrogen for growth. Because cyanide, as KCN or NaCN, is toxic for growth, the bacteria (Pseudomonas fluorescens) have to be grown in fed-batch culture with cyanide as the limiting nutrient. Cyanide is converted to carbon dioxide and ammonia (which is then assimilated) by an NADH-linked cyanide oxygenase system.
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Affiliation(s)
- C J Knowles
- Biological Laboratory, University of Kent, Canterbury, UK
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Tahboub YR, Galijasevic S, Diamond MP, Abu-Soud HM. Thiocyanate modulates the catalytic activity of mammalian peroxidases. J Biol Chem 2005; 280:26129-36. [PMID: 15894800 DOI: 10.1074/jbc.m503027200] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We investigated the potential role of the co-substrate, thiocyanate (SCN-), in modulating the catalytic activity of myeloperoxidase (MPO) and other members of the mammalian peroxidase superfamily (lactoperoxidase (LPO) and eosinophil peroxidase (EPO)). Pre-incubation of SCN- with MPO generates a more complex biological setting, because SCN- serves as either a substrate or inhibitor, causing diverse impacts on the MPO heme iron microenvironment. Consistent with this hypothesis, the relationship between the association rate constant of nitric oxide binding to MPO-Fe(III) as a function of SCN- concentration is bell-shaped, with a trough comparable with normal SCN- plasma levels. Rapid kinetic measurements indicate that MPO, EPO, and LPO Compound I formation occur at rates slower than complex decay, and its formation serves to simultaneously catalyze SCN- via 1e- and 2e- oxidation pathways. For the three enzymes, Compound II formation is a fundamental feature of catalysis and allows the enzymes to operate at a fraction of their possible maximum activities. MPO and EPO Compound II is relatively stable and decays gradually within minutes to ground state upon H2O2 exhaustion. In contrast, LPO Compound II is unstable and decays within seconds to ground state, suggesting that SCN- may serve as a substrate for Compound II. Compound II formation can be partially or completely prevented by increasing SCN- concentration, depending on the experimental conditions. Collectively, these results illustrate for the first time the potential mechanistic differences of these three enzymes. A modified kinetic model, which incorporates our current findings with the mammalian peroxidases classic cycle, is presented.
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Affiliation(s)
- Yahya R Tahboub
- Department of Obstetrics and Gynecology, The C. S. Mott Center for Human Growth and Development, Wayne State University, Detroit, Michigan 48201, USA
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Abstract
The biokinetic parameters for autotrophic systems are difficult to obtain and are often mistakenly determined because the size of the autotrophic population in mixed (i.e., heterotrophic and autotrophic) cultures cannot be accurately estimated. This article presents a systematic approach, combining bioenergetic calculations and experimental data, to obtain values of the biokinetic parameters pertinent to the aerobic, autotrophic biodegradation of thiocyanate. Nonlinear regression techniques were employed using both initial thiocyanate utilization rate data and single thiocyanate depletion curves. Both types of data were necessary to overcome the problems arising from the linear nature of the substrate depletion curves and the high correlation of the biokinetic model parameters inherent in nonlinear regression analysis. The aerobic biodegradation of thiocyanate followed a substrate inhibition pattern that was successfully described by the Haldane-Andrews model. Although regression analysis did not yield unique biokinetic parameter estimates, the following parameter value ranges were obtained: maximum specific substrate utilization rate (k), 0.26 to 0.44 mg SCN-/mg biomass h; half-saturation coefficient (Ks), 2.3 to 7.1 mg SCN-/L; and inhibition coefficient (Ki), 28 to 109 mg SCN-/L. Based on the estimated biokinetic parameter values, a design and operation diagram was constructed that depicts the steady-state thiocyanate concentration as a function of solids retention time for a completely mixed, continuous-flow reactor.
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Affiliation(s)
- C H Hung
- School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0512, USA
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17
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Katayama Y, Matsushita Y, Kaneko M, Kondo M, Mizuno T, Nyunoya H. Cloning of genes coding for the three subunits of thiocyanate hydrolase of Thiobacillus thioparus THI 115 and their evolutionary relationships to nitrile hydratase. J Bacteriol 1998; 180:2583-9. [PMID: 9573140 PMCID: PMC107207 DOI: 10.1128/jb.180.10.2583-2589.1998] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Thiocyanate hydrolase is a newly found enzyme from Thiobacillus thioparus THI 115 that converts thiocyanate to carbonyl sulfide and ammonia (Y. Katayama, Y. Narahara, Y. Inoue, F. Amano, T. Kanagawa, and H. Kuraishi, J. Biol. Chem. 267:9170-9175, 1992). We have cloned and sequenced the scn genes that encode the three subunits of the enzyme. The scnB, scnA, and scnC genes, arrayed in this order, contained open reading frames encoding sequences of 157, 126, and 243 amino acid residues, respectively, for the beta, alpha, and gamma subunits, respectively. Each open reading frame was preceded by a typical Shine-Dalgarno sequence. The deduced amino-terminal peptide sequences for the three subunits were in fair agreement with the chemically determined sequences. The protein molecular mass calculated for each subunit was compatible with that determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. From a computer analysis, thiocyanate hydrolase showed significant homologies to bacterial nitrile hydratases known to convert nitrile to the corresponding amide, which is further hydrolyzed by amidase to form acid and ammonia. The two enzymes were homologous over regions corresponding to almost the entire coding regions of the genes: the beta and alpha subunits of thiocyanate hydrolase were homologous to the amino- and carboxyl-terminal halves of the beta subunit of nitrile hydratase, and the gamma subunit of thiocyanate hydrolase was homologous to the alpha subunit of nitrile hydratase. Comparisons of the catalytic properties of the two homologous enzymes support the model for the reaction steps of thiocyanate hydrolase that was previously presented on the basis of biochemical analyses.
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Affiliation(s)
- Y Katayama
- Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183, Japan.
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Borowitz JL, Gunasekar PG, Isom GE. Hydrogen cyanide generation by mu-opiate receptor activation: possible neuromodulatory role of endogenous cyanide. Brain Res 1997; 768:294-300. [PMID: 9369328 DOI: 10.1016/s0006-8993(97)00659-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Hydrogen cyanide, a gaseous molecule, is produced by white blood cells during phagocytosis. The present study examined the possibility that neuronal-like cells may also produce cyanide following activation. Rat pheochromocytoma (PC12) cells exhibited a low level of cyanide generation that was significantly increased by mu-opiate agonists (hydromorphone, morphine) and blocked by naloxone. A variety of other agonists including bradykinin, nicotine and glutamate did not generate cyanide in PC12 cells. Systemic administration of hydromorphone to rats increased brain cyanide levels by 61% after 15 min. Using microdialysis probes implanted in the cortical-hippocampal areas of the anesthetized rat or in the hypothalamus of the conscious hamster, a 2- to 5-fold increase in cyanide generation was seen after hydromorphone administration and this increase was blocked by naloxone. To determine whether cyanide release by hydromorphone has functional significance in a neuronal system, cyanide enhancement of N-methyl-D-aspartate (NMDA)-induced increased [Ca2+]i was measured in rat cerebellar granule cells. Hydromorphone enhanced the response to NMDA similar to cyanide and the hydromorphone effect was blocked by cyanide scavengers. These data show that cyanide generation is increased in neuronal tissue by a mu-opiate receptor agonist and it is proposed that endogenous cyanide may modulate the NMDA receptor response.
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Affiliation(s)
- J L Borowitz
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA
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Adak S, Mazumdar A, Banerjee RK. Low catalytic turnover of horseradish peroxidase in thiocyanate oxidation. Evidence for concurrent inactivation by cyanide generated through one-electron oxidation of thiocyanate. J Biol Chem 1997; 272:11049-56. [PMID: 9110998 DOI: 10.1074/jbc.272.17.11049] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The catalytic turnover of horseradish peroxidase (HRP) to oxidize SCN- is a hundredfold lower than that of lactoperoxidase (LPO) at optimum pH. While studying the mechanism, HRP was found to be reversibly inactivated following pseudo-first order kinetics with a second order rate constant of 400 M-1 min-1 when incubated with SCN- and H2O2. The slow rate of SCN- oxidation is increased severalfold in the presence of free radical traps, 5-5-dimethyl-1-pyrroline N-oxide or alpha-phenyl-tert-butylnitrone, suggesting the plausible role of free radical or radical-derived product in the inactivation. Spectral studies indicate that SCN- at a lower concentrations slowly reduces compound II to native state by one-electron transfer as evidenced by a time-dependent spectral shift from 418 to 402 nm through an isosbestic point at 408 nm. In the presence of higher concentrations of SCN-, a new stable Soret peak appears at 421 nm with a visible peak at 540 nm, which are the characteristics of the inactivated enzyme. The one-electron oxidation product of SCN- was identified by electron spin resonance spectroscopy as 5-5-dimethyl-1-pyrroline N-oxide adduct of the sulfur-centered thiocyanate radical (aN = 15.0 G and abetaH = 16.5 G). The inactivation of the enzyme in the presence of SCN- and H2O2 is prevented by electron donors such as iodide or guaiacol. Binding studies indicate that both iodide and guaiacol compete with SCN- for binding at or near the SCN- binding site and thus prevent inactivation. The spectral characteristics of the inactivated enzyme are exactly similar to those of the native HRP-CN- complex. Quantitative measurements indicate that HRP produces a 10-fold higher amount of CN- than LPO when incubated with SCN- and H2O2. As HRP has higher affinity for CN- than LPO, it is concurrently inactivated by CN- formed during SCN- oxidation, which is not observed in case of LPO. This study further reveals that HRP catalyzes SCN- oxidation by two one-electron transfers with the intermediate formation of thiocyanate radicals. The radicals dimerize to form thiocyanogen, (SCN)2, which is hydrolyzed to form CN-. As LPO forms OSCN- as the major stable oxidation product through a two-electron transfer mechanism, it is not significantly inactivated by CN- formed in a small quantity.
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Affiliation(s)
- S Adak
- Department of Physiology, Indian Institute of Chemical Biology, Calcutta 700 032, India
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Pollock JR, Goff HM. Lactoperoxidase-catalyzed oxidation of thiocyanate ion: a carbon-13 nuclear magnetic resonance study of the oxidation products. BIOCHIMICA ET BIOPHYSICA ACTA 1992; 1159:279-85. [PMID: 1390933 DOI: 10.1016/0167-4838(92)90057-k] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Products formed from the lactoperoxidase (LPO) catalyzed oxidation of thiocyanate ion (SCN-) with hydrogen peroxide (H2O2) have been studied by 13C-NMR at pH 6 and pH 7. Ultimate formation of hypothiocyanite ion (OSCN-) as the major product correlates well with the known optical studies. The oxidation rate of SCN- appears to be greater at pH < or = 6.0. At [H2O2]/[SCN-] ratios of < or = 0.5, OSCN- is not formed immediately, but an unidentified intermediate is produced. At [H2O2]/[SCN-] > 0.5, SCN- appears to be directly oxidized to OSCN-. Once formed, OSCN- slowly degrades over a period of days to carbon dioxide (CO2), bicarbonate ion (HCO3-), and hydrogen cyanide (HCN). An additional, previously unrecognized product also appears after formation of OSCN-. On the basis of carbon-13 chemical shift information this new species is suggested to result from rearrangement of OSCN- to yield the thiooxime isomer, SCNO- or SCNOH.
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Affiliation(s)
- J R Pollock
- Department of Chemistry, University of Iowa, Iowa City 52242
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Katayama Y, Narahara Y, Inoue Y, Amano F, Kanagawa T, Kuraishi H. A thiocyanate hydrolase of Thiobacillus thioparus. A novel enzyme catalyzing the formation of carbonyl sulfide from thiocyanate. J Biol Chem 1992. [DOI: 10.1016/s0021-9258(19)50404-5] [Citation(s) in RCA: 96] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Modi S, Behere DV, Mitra S. Horseradish peroxidase catalyzed oxidation of thiocyanate by hydrogen peroxide: comparison with lactoperoxidase-catalysed oxidation and role of distal histidine. BIOCHIMICA ET BIOPHYSICA ACTA 1991; 1080:45-50. [PMID: 1932081 DOI: 10.1016/0167-4838(91)90110-l] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Horseradish peroxidase-catalysed oxidation of thiocyanate by hydrogen peroxide has been studied by 15N-NMR and optical spectroscopy at different concentrations of thiocyanate and hydrogen peroxide and at different pH values. The extent of the oxidation and the identity of the oxidized product of the thiocyanate has been investigated in the SCN-/H2O2/HRP system and compared with the corresponding data on the SCN-/H2O2/LPO system. The NMR studies show that (SCN)2 is the oxidation product of thiocyanate in the SCN-/H2O2/HRP system, and its formation is maximum at pH less than or equal to 4 and that the oxidation does not take place at pH greater than or equal to 6. Since thiocyanate does not bind to HRP at pH greater than or equal to 6 (Modi et al. (1989) J. Biol. Chem. 264, 19677-19684), the binding of thiocyanate to HRP is considered to be a prerequisite for the oxidation of thiocyanate. It is further observed that at [H2O2]/[SCN-] = 4, (SCN)2 decomposes very slowly back to thiocyanate. The oxidation product of thiocyanate in the SCN-/H2O2/LPO system has been shown to be HOSCN/OSCN- which shows maximum inhibition of uptake by Streptococcus cremoris 972 bacteria when hydrogen peroxide and thiocyanate are present in equimolar amounts (Modi et al. (1991) Biochemistry 30, 118-124). However, in case of HRP no inhibition of oxygen uptake by this bacteria was observed. Since thiocyanate binds to LPO at the distal histidine while to HRP near 1- and 8-CH3 heme groups, the role of distal histidine in the activity of SCN-/H2O2/(LPO, HRP) systems is indicated.
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Affiliation(s)
- S Modi
- Chemical Physics Group, Tata Institute of Fundamental Research, Bombay, India
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Modi S, Behere DV, Mitra S. Binding of thiocyanate to lactoperoxidase: 1H and 15N nuclear magnetic resonance studies. Biochemistry 1989; 28:4689-94. [PMID: 2548589 DOI: 10.1021/bi00437a027] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The binding of thiocyanate to lactoperoxidase (LPO) has been investigated by 1H and 15N NMR spectroscopy. 1H NMR of LPO shows that the major broad heme methyl proton resonance at about 61 ppm is shifted upfield by addition of the thiocyanate, indicating binding of the thiocyanate to the enzyme. The pH dependence of line width of 15N resonance of SC15N- in the presence of the enzyme has revealed that the binding of the thiocyanate to the enzyme is facilitated by protonation of an ionizable group (with pKa of 6.4), which is presumably distal histidine. Dissociation constants (KD) of SC15N-/LPO, SC15N-/LPO/I-, and SC15N-/LPO/CN- equilibria have been determined by 15N T1 measurements and found to be 90 +/- 5, 173 +/- 20, and 83 +/- 6 mM, respectively. On the basis of these values of KD, it is suggested that the iodide ion inhibits the binding of the thiocyanate but cyanide ion does not. The thiocyanate is shown to bind at the same site of LPO as iodide does, but the binding is considerably weaker and is away from the ferric ion. The distance of 15N of the bound thiocyanate ion from the iron is determined to be 7.2 +/- 0.2 A from the 15N T1 measurements.
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Affiliation(s)
- S Modi
- Chemical Physics Group, Tata Institute of Fundamental Research, Bombay, India
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Abstract
The excretion of hydrogen cyanide in breath and blood concentrations of cyanide were measured in eight normal subjects. There was no correlation between breath and blood levels of cyanide. Furthermore, breath cyanide concentrations calculated from blood values were much lower than measured values, which suggested a local production of hydrogen cyanide in the oropharynx. When saliva was incubated at 37 degrees C hydrogen cyanide was formed in the presence of air but not in a nitrogen atmosphere. No hydrogen cyanide was formed with boiled saliva and the production of hydrogen cyanide by native saliva was inhibited by catalase and by 6-n-propyl-thiouracil. Centrifugation of saliva resulted in a supernatant and a sediment, which were both required for the formation of hydrogen cyanide. Dialysis of the supernatant abolished its cyanide forming ability, which could be restored by addition of thiocyanate. We conclude that most of the hydrogen cyanide found in breath from normal human beings originates from oxidation of thiocyanate by salivary peroxidase in the oropharynx. As a consequence measurements of breath hydrogen cyanide can only be used to detect heavy exposure to cyanide.
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Affiliation(s)
- P Lundquist
- Department of Clinical Chemistry, Linköping University, Uppsala, Sweden
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Stelmaszyńska T. Formation of HCN and its chlorination to ClCN by stimulated human neutrophils--2. Oxidation of thiocyanate as a source of HCN. THE INTERNATIONAL JOURNAL OF BIOCHEMISTRY 1986; 18:1107-14. [PMID: 3028884 DOI: 10.1016/0020-711x(86)90084-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Leucocytes challenged by Staphylococcus epidermidis or stimulated by phorbol myristate acetate (PMA) produce cyanide from thiocyanate. The amount of H14CN formed depends on KS14CN concentration and is enhanced by pretreatment of phagocytosed bacteria with penicillin or by adding amine-taurine to the medium of PMA-stimulated neutrophils. The reaction of taurine chloramine or chlorinated Staphylococcus epidermidis (containing N-Cl groups) with thiocyanate results in HCN formation. At higher concentration of chloramine cyanogen chloride is formed. Cyanide is chlorinated by PMA-stimulated neutrophils and this process is significantly enhanced by exogenous taurine and inhibited by 3-amino 1,2,4-triazole. It is conceivable that oxidation of thiocyanate to HCN and chlorination of HCN to ClCN is mediated by the chlorinating species (taurine chloramine) produced by stimulated neutrophils.
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Carlsson J, Edlund MB, Hänström L. Bactericidal and cytotoxic effects of hypothiocyanite-hydrogen peroxide mixtures. Infect Immun 1984; 44:581-6. [PMID: 6724690 PMCID: PMC263633 DOI: 10.1128/iai.44.3.581-586.1984] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Lactoperoxidase catalyzes the oxidation of thiocyanate by hydrogen peroxide into hypothiocyanite, a reaction which can protect bacterial and mammalian cells from killing by hydrogen peroxide. The present study demonstrates, however, that lactoperoxidase in the presence of thiocyanate can actually potentiate the bactericidal and cytotoxic effects of hydrogen peroxide under specific conditions, such as when hydrogen peroxide is present in the reaction mixtures in excess of thiocyanate. The toxic agent was also formed in the absence of lactoperoxidase in a reaction between hypothiocyanite and hydrogen peroxide. Sulfate, sulfite, cyanate, carbonate, and ammonia, which have been postulated to be formed in the chemical oxidation of hypothiocyanite by hydrogen peroxide, were not bactericidal and did not potentiate the bactericidal effect of hydrogen peroxide. Cyanosulfurous acid, the only other postulated product of the chemical oxidation of hypothiocyanite by hydrogen peroxide, may be the killing agent.
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Weuffen W, Franzke C, Thürkow B. [The alimentary ingestion, analysis and biological significance of thiocyanate]. DIE NAHRUNG 1984; 28:341-55. [PMID: 6382017 DOI: 10.1002/food.19840280403] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A survey is given of the alimentary ingestion, metabolization and elimination as well as of the biological significance of thiocyanate (SCN-) in the mammalian organism. SCN- is an important nutritional factor since it influences essential bodily functions, e.g. immune response. Its analytical determination in vegetable and animal foodstuffs may be considerably affected by the reversible binding of SCN- to protein molecules and by natural products, e.g. amino acids and cyanide, from glycosidic precursors, which interfere with the reaction with bromine. This will be combining paper chromatography with gas chromatography. Except Brassica species which are relatively high in SCN- in glycosidic combination, vegetable foodstuffs contain nearly 0.1-1.3 mg SCN-/kg fresh material; animal foodstuffs, e.g. beef, contains 0.5-0.7 mg SCN-/kg. Balances calculations have shown that in non-smokers the average alimentary ingestion ranges from 1.8 to 5.2 mg SCN-/d.
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Pruitt KM, Tenovuo J. Kinetics of hypothiocyanite production during peroxidase-catalyzed oxidation of thiocyanate. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 704:204-14. [PMID: 7104367 DOI: 10.1016/0167-4838(82)90147-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We report here a kinetic study of the generation of hypothiocyanite (OSCN-), a product of lactoperoxidase-catalyzed oxidation of thiocyanate ion. Previous studies have measured OSCN- by reactions involving the oxidation of sulfhydryl compounds. Our results show that a more suitable kinetic analysis of OSCN- can be based on absorbance changes measured at 235 nm. About 90% of the oxidation products of SCN- observed at 235 nm were reactive with sulfhydryls and could be reduced with 2-mercaptoethanol. Both thiocyanate and peroxide were rate-limiting and the formation of OSCN- was proportional to the initial concentration of H2O2 until an equimolar concentration of H2O2 and SCN- was reached. This equimolar concentration gave the maximum generation of OSCN-. High concentrations (greater than 100 micrograms/ml) of lactoperoxidase decreased OSCN- generation, but only if the SCN- was added to the enzyme prior to addition of H2O2. With lactoperoxidase concentrations exceeding 1 microgram/ml, the reaction velocity was rapid, but the decay of OSCN- was slow. Free H2O2 in the reaction mixture always resulted in rapid decay of OSCN-. Addition of varying concentrations of peroxide to solutions containing 1 microgram/ml of enzyme and [SCN-] = 5 mM gave a family of hyperbolic A235 vs. time curves. Both the initial slopes and the plateaus of these curves increased linearly with increasing initial peroxide concentrations up to [H2O2] = 0.4 mM, remained relatively constant in the range [H2O2] = 0.4 to 0.8 mM, and decreased rapidly above [H2O2] = 0.8 mM. These results are consistent with the following kinetic model: Hydrogen peroxide reacts rapidly with lactoperoxidase to produce compound I. This compound I oxidizes SCN- to OSCN- and also oxidizes OSCN- to O2SCN-. The OSCN- also reacts with SCN-. The formation of OSCN- is associated with the appearance of an absorbance peak at 225-235 nm. The oxidation of OSCN- by excess peroxide or its decomposition at high concentrations is associated with a decrease in A235 and the appearance of a peak at 245-255 nm. The extinction coefficient for OSCN- was determined to be 1.29 x 10(3) M-1 . cm-1. The second-order rate constant for the oxidation of thiocyanate by compound I was estimated to be 2 x 10(5) M-1 . s-1.
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Pruitt KM, Tenovuo J, Andrews RW, McKane T. Lactoperoxidase-catalyzed oxidation of thiocyanate: polarographic study of the oxidation products. Biochemistry 1982; 21:562-7. [PMID: 7066307 DOI: 10.1021/bi00532a023] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The lactoperoxidase-catalyzed oxidation of thiocyanate (SCN-) was studied by two different polarographic techniques: direct current polarography and linear sweep voltammetry. The main oxidation product at pH 6.5, with a half-wave potential (E1/2) of -0.39 to -0.44 V, was identified as hypothiocyanite (OSCN-) ion. The E1/2 for OSCN- was not available in the literature. The identification of OSCN- was based on a close correlation between the current of the OSCN- peak and the concentration of chemically assayed OSCN-. Also the specific rates of decay of the current and that of chemically detectable OSCN- were similar, and both curves followed apparent first-order kinetics. Subsequently, the addition of a reducing agent (2-mercaptoethanol) resulted in immediate disappearance of both chemically detectable OSCN- and the OSCN- wave in the polarograms. All three components of the lactoperoxidase (LPO) system (SCN-, H2O2, and LPO) were needed to produce the OSCN- peak. Addition of excess H2O2 or H2O2-LPO to an OSCN--SCN- mixture resulted in a formation of a new peak with a characteristic peak potential (Ep) of -0.20 to -0.25 V. The generation of this new peak was associated with a simultaneous, markedly enhanced decrease of OSCN- concentration, indicating a possible reaction between H2O2 (or H2O2-LPO) and OSCN-. No equivalent reaction was obtained by the addition of buffer alone. This new peak may represent higher oxy acids of SCN- (O2SCN-, O3SCN-), formed in the oxidation of OSCN- by H2O2 or by H2O2-LPO. This type of reaction can explain why, in solutions which already contain OSCN- (e.g., in saliva), the addition of H2O2 results in the formation of highly reactive, short-lived antimicrobial products in addition to OSCN-.
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Thomas EL. Lactoperoxidase-catalyzed oxidation of thiocyanate: equilibria between oxidized forms of thiocyanate. Biochemistry 1981; 20:3273-80. [PMID: 7248282 DOI: 10.1021/bi00514a045] [Citation(s) in RCA: 133] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Virion A, Deme D, Pommier J, Nunez J. Opposite effects of thiocyanate on tyrosine iodination and thyroid hormone synthesis. EUROPEAN JOURNAL OF BIOCHEMISTRY 1980; 112:1-7. [PMID: 7449758 DOI: 10.1111/j.1432-1033.1980.tb04979.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The effect of a pseudohalide, SCN-, an anion with the same molecular size as iodide, was studied on two reactions: thyroglobulin iodination and thyroid hormone synthesis (coupling reaction) catalyzed by peroxidases. The coupling reaction was studied separately from the iodination reaction by using labelled thyroglobulin samples previously iodinated but containing little or no hormones. 1. SCN- inhibits iodide oxidation (I- leads to I2) whatever the enzyme, thyroid, lactoperoxidase or horseradish peroxidase. The amount of SCN- required to completely inhibit this reaction varies depending on the enzyme. Similarly tyrosine iodination is inhibited by SCN- with large variations, depending on the peroxidase, in the concentration of this anion required for inhibition. 2. In contrast SCN- stimulates the coupling reaction: (a) this affect is seen with the thyroid and lactoperoxidases but not with horseradish peroxidase; (b) the concentration of SCN- required for half-maximal stimulation of the coupling reaction is much lower (0.5-1 microM) than that required for the inhibition of iodide oxidation (60-80 microM); (c) ClO4(-), an anion with the same molecular size as SCN- and I-, has no effect on the coupling reaction; (d) this stimulatory effect of SCN- does not depend on a modification of the thyroglobulin molecule since it is not seen with horseradish peroxidase or in purely chemical coupling conditions. 3. The stimulatory effect of SCN- is therefore seen as resulting from the binding of this anion to a limited number of high-affinity sites present at the surface of both thyroid and lactoperoxidases. The inhibitory effect depends, in contrast, on the binding of SCN- to the substrate site with lower affinities. Since iodide also behaves both as a substrate for the iodination reaction and as a stimulatory ligand for the coupling reaction, these data provide further support in favour of the existence of an enzyme-iodide (or SCN-) complex with catalytic properties different from those of the native peroxidase.
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Tenovuo J. Inhibition by thiocyanate of lactoperoxidase-catalysed oxidation and iodination reactions. Arch Oral Biol 1978; 23:899-903. [PMID: 33640 DOI: 10.1016/0003-9969(78)90294-7] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Abstract
The amount of cyanide released on acidifying whole blood was much greater than the total from the plasma and red cells assayed separately, and varied directly with plasma thiocyanate concentrations. This artifactual formation of cyanide by whole blood was reduced by exposure to carbon monoxide. Incubation of haemolysates of washed red blood cells showed that optimum cyanide production from thiocyanate occurred at pH 4.5 with none at pH 7.4; spectrophotometric study confirmed the involvement of haemoglobin. It is doubtful whether this activity of haemoglobin is of normal physiological importance and it is probable that the evidence for the enzyme, 'thiocyanate oxidase' was based on this artifact of assay. Plasma cyanide is probably the metabolically relevant measurement, since the red blood cells act as a 'cyanide sink'. Where values for whole blood cyanide are required we recommend separate assay of plasma and saline washed red blood cells.
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Tenovuo J, Knuuttila ML. The antibacterial action of the various components of the lactoperoxidase system on a cariogenic strain of Streptococcus mutans. J Dent Res 1977; 56:1603-7. [PMID: 277482 DOI: 10.1177/00220345770560123201] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Physiological activity of lactoperoxidase and in vivo concentration of thiocyanate ions were shown to be inhibitory against a cariogenic strain of Streptococcus mutans. However, the amount of H2O2 in vivo may be too low for optimum inhibition by lactoperoxidase system. H2O2 alone also inhibited the growth of S mutants to some degree.
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Mickelson MN. Glucose transport in Streptococcus agalactiae and its inhibition by lactoperoxidase-thiocyanate-hydrogen peroxide. J Bacteriol 1977; 132:541-8. [PMID: 334746 PMCID: PMC221894 DOI: 10.1128/jb.132.2.541-548.1977] [Citation(s) in RCA: 41] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Transport of 2-deoxyglucose or glucose in Streptococcus agalactiae was strongly inhibited if the cells were first exposed to a combination of lactoperoxidase-thiocyanate-hydrogen peroxide (LP-complex). The inhibition was completely reversible with dithiothreitol. N-ethylmaleimide and p-chloromercuribenzoate inhibited sugar transport, and the inhibition was also reversible with dithiothreitol. Sodium fluoride also inhibited sugar transport. Glucolysis was completely inhibited, and dithiothreitol completely reversed the inhibition. Phosphoenolpyruvate-dependent phosphotransferase activity in S. agalactiae was not strongly inhibited by the LP-complex. Interference of the entry of glucose into cells of S. agalactiae by the LP-complex could well account for its growth inhibitory properties with this organism. The inhibition of glucose transport by the LP-complex and its reversibility with dithiothreitol suggest the modification of functional sulfhydryl groups in the cell membrane as a cause of transport inhibition.
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Aune TM, Thomas EL. Accumulation of hypothiocyanite ion during peroxidase-catalyzed oxidation of thiocyanate ion. EUROPEAN JOURNAL OF BIOCHEMISTRY 1977; 80:209-14. [PMID: 562752 DOI: 10.1111/j.1432-1033.1977.tb11873.x] [Citation(s) in RCA: 212] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Colson-Guastalla H, Aymard C, Chambon JP, Michel F. Studies on free or haptoglobin-bound hemoglobin and derivatives (semihemoglobins and porphyrinated semihemoglobins). Some aspects of their peroxidatic activity. Biochimie 1975; 57:1035-44. [PMID: 1222141 DOI: 10.1016/s0300-9084(75)80359-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The peroxidatic activity of hemoglobin (Hb) is known to be enhanced when this hemoprotein is bound to haptoglobin (Hp). The peroxidatic reaction (H2O2, guaiacol as donor) has been kinetically studied (Steady-state) in the presence of free or rabbit-haptoglobin bound human hemoglobin and some of its derivatives, all in ferricyano-form. With free Hb+ CN, we observed linearity of Lineweaver and Burk plots in a wide range of concentrations, the donor's behaviour was therefore assumed to obey the Michaelis-Menten mechanism. When Hp-Hb+ CN is the enzyme, the donor's behaviour is more complicated, analysis shows the existence of two kinds of donor's binding sites. The possibility whether this behaviour might correspond to the intrinsic properties of Hb chains, as revealed after combination with Hp, was examined. The peroxidatic activity of free and Hp-bound alpha and beta chains of Hb were studied. The alpha chains of Hb combine with Hp whereas the beta chains fail to do so. In order to make useful comparisons, the peroxidatic activity of Hp-bound alpha and beta chains were studied by the use of Hp-semihemoglobin complexes where the semihemoglobins carried heme on only one type of chain (alpha or beta). Results did not show an evident correlation between the activities of the two free or bound types of chains and those of the two classes of binding sites revealed in Hp-Hb+ CN. Moreover, it appeared that the heme-free complementary chain might influence the activity of the heme-carrying alpha or beta chain in semihemoglobins and Hp-semihemoglobin complexes. The binding or protoporphyrin on free and Hp-bound semihemoglobins leads to species which exhibit structures close to that of Hb and Hp-Hb complex respectivley. Results of studies on these derivatives brought up new interesting data : when the porphyrin ring alone is bound to the heme deficient chains (alpha or beta), in Hp-semihemoglobin complexes, the same peculiar behaviour, already observed with Hp-Hb complex, is found again. The structural implications of these results are discussed.
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