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Tracz A, Malinowska M, Leśniak S, Zawisza A. Aziridine Ring Opening as Regio- and Stereoselective Access to C-Glycosyl-Aminoethyl Sulfide Derivatives. Molecules 2022; 27:1764. [PMID: 35335129 PMCID: PMC8952378 DOI: 10.3390/molecules27061764] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2022] [Revised: 03/01/2022] [Accepted: 03/06/2022] [Indexed: 11/18/2022] Open
Abstract
A short synthetic route to stereoselective access to C-glycosyl-aminoethyl sulfide derivatives has been developed through the reaction of tributhyltin derivatives of glycals with aziridinecarboaldehyde and the regioselective ring opening of a chiral aziridine with thiophenol. The absolute configurations of the resulting diastereoisomers were determined by 1H NMR spectroscopy.
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Affiliation(s)
| | | | | | - Anna Zawisza
- Department of Organic and Applied Chemistry, University of Łódź, 91-403 Łódź, Poland; (A.T.); (M.M.); (S.L.)
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2
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Itoh S, Abe T, Morimoto Y, Sugimoto H. 2-(2-Pyridyl)ethylamine (Pye) ligands in copper(I)-dioxygen chemistry. Inorganica Chim Acta 2018. [DOI: 10.1016/j.ica.2017.09.017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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3
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Quist DA, Diaz DE, Liu JJ, Karlin KD. Activation of dioxygen by copper metalloproteins and insights from model complexes. J Biol Inorg Chem 2017; 22:253-288. [PMID: 27921179 PMCID: PMC5600896 DOI: 10.1007/s00775-016-1415-2] [Citation(s) in RCA: 163] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Accepted: 11/11/2016] [Indexed: 02/08/2023]
Abstract
Nature uses dioxygen as a key oxidant in the transformation of biomolecules. Among the enzymes that are utilized for these reactions are copper-containing metalloenzymes, which are responsible for important biological functions such as the regulation of neurotransmitters, dioxygen transport, and cellular respiration. Enzymatic and model system studies work in tandem in order to gain an understanding of the fundamental reductive activation of dioxygen by copper complexes. This review covers the most recent advancements in the structures, spectroscopy, and reaction mechanisms for dioxygen-activating copper proteins and relevant synthetic models thereof. An emphasis has also been placed on cofactor biogenesis, a fundamentally important process whereby biomolecules are post-translationally modified by the pro-enzyme active site to generate cofactors which are essential for the catalytic enzymatic reaction. Significant questions remaining in copper-ion-mediated O2-activation in copper proteins are addressed.
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Affiliation(s)
- David A Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Daniel E Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Jeffrey J Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.
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4
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Becerra-Cely L, Rueda-Espinosa J, Ojeda-Porras A, Gamba-Sánchez D. Insights into the Pummerer synthesis of oxazolines. Org Biomol Chem 2016; 14:8474-85. [PMID: 27537270 DOI: 10.1039/c6ob01666a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
A rapid and simple method to access unnatural 2-substituted 5-thio oxazolines has been developed. This methodology is based on a Pummerer reaction followed by an intramolecular nucleophilic substitution, which changes the paradigm for the normal use of a base in Pummerer chemistry. We also provide a useful two-step method for the synthesis of the starting material and a mechanistic proposal based on experimental observations, which contests the previously proposed reaction pathway. The reaction proved to be general, and different substituents, such as alkyl, aryl, alkenyl and functionalized groups, can be used without a significant decrease in efficiency.
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Affiliation(s)
- Laura Becerra-Cely
- Laboratory of Organic Synthesis, Bio and Organocatalysis, Chemistry Department, Universidad de los Andes, Cra 1 No. 18A-12 Q:305, Bogotá 111711, Colombia.
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5
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Abstract
Primary copper(I)-dioxygen (O2) adducts, cupric-superoxide complexes, have been proposed intermediates in copper-containing dioxygen-activating monooxygenase and oxidase enzymes. Here, mechanisms of C-H activation by reactive copper-(di)oxygen intermediates are discussed, with an emphasis on cupric-superoxide species. Over the past 25 years, many synthetically derived cupric-superoxide model complexes have been reported. Due to the thermal instability of these intermediates, early studies focused on increasing their stability and obtaining physical characterization. More recently, in an effort to gain insight into the possible substrate oxidation step in some copper monooxygenases, several cupric-superoxide complexes have been used as surrogates to probe substrate scope and reaction mechanisms. These cupric superoxides are capable of oxidizing substrates containing weak O-H and C-H bonds. Mechanistic studies for some enzymes and model systems have supported an initial hydrogen-atom abstraction via the cupric-superoxide complex as the first step of substrate oxidation.
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Affiliation(s)
- Jeffrey J Liu
- Department of Chemistry, Johns Hopkins University, Baltimore MD 21218 (USA)
| | - Daniel E Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore MD 21218 (USA)
| | - David A Quist
- Department of Chemistry, Johns Hopkins University, Baltimore MD 21218 (USA)
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore MD 21218 (USA)
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6
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Vandenbossche E, Lucas C, Mistry L, Garfield E, Mitchell SC, Steventon GB. Phenylalanine monooxygenase and the sulfur oxygenation of S-carboxymethyl-l-cysteine in mice. Xenobiotica 2015; 46:379-84. [DOI: 10.3109/00498254.2015.1075259] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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7
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Itoh S. Developing mononuclear copper-active-oxygen complexes relevant to reactive intermediates of biological oxidation reactions. Acc Chem Res 2015; 48:2066-74. [PMID: 26086527 DOI: 10.1021/acs.accounts.5b00140] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Active-oxygen species generated on a copper complex play vital roles in several biological and chemical oxidation reactions. Recent attention has been focused on the reactive intermediates generated at the mononuclear copper active sites of copper monooxygenases such as dopamine β-monooxygenase (DβM), tyramine β-monooxygenase (TβM), peptidylglycine-α-hydroxylating monooxygenase (PHM), and polysaccharide monooxygenases (PMO). In a simple model system, reaction of O2 and a reduced copper(I) complex affords a mononuclear copper(II)-superoxide complex or a copper(III)-peroxide complex, and subsequent H(•) or e(-)/H(+) transfer, which gives a copper(II)-hydroperoxide complex. A more reactive species such as a copper(II)-oxyl radical type species could be generated via O-O bond cleavage of the peroxide complex. However, little had been explored about the chemical properties and reactivity of the mononuclear copper-active-oxygen complexes due to the lack of appropriate model compounds. Thus, a great deal of effort has recently been made to develop efficient ligands that can stabilize such reactive active-oxygen complexes in synthetic modeling studies. In this Account, I describe our recent achievements of the development of a mononuclear copper(II)-(end-on)superoxide complex using a simple tridentate ligand consisting of an eight-membered cyclic diamine with a pyridylethyl donor group. The superoxide complex exhibits a similar structure (four-coordinate tetrahedral geometry) and reactivity (aliphatic hydroxylation) to those of a proposed reactive intermediate of copper monooxygenases. Systematic studies based on the crystal structures of copper(I) and copper(II) complexes of the related tridentate supporting ligands have indicated that the rigid eight-membered cyclic diamine framework is crucial for controlling the geometry and the redox potential, which are prerequisites for the generation of such a unique mononuclear copper(II)-(end-on)superoxide complex. Reactivity of a mononuclear copper(II)-alkylperoxide complex has also been examined to get insights into the intrinsic reactivity of copper(II)-peroxide species, which is usually considered as a sluggish oxidant or just a precursor of copper-oxyl radical type reactive species. However, our studies have unambiguously demonstrated that copper(II)-alkylperoxide complex can be a direct oxidant for C-H bond activation of organic substrates, when the C-H bond activation is coupled with O-O bond cleavage (concerted mechanism). The reactivity studies of these mononuclear copper(II) active-oxygen species (superoxide and alkylperoxide) will provide significantly important insights into the catalytic mechanism of copper monooxygenases as well as copper-catalyzed oxidation reactions in synthetic organic chemistry.
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Affiliation(s)
- Shinobu Itoh
- Department of Material and
Life Science, Division of Advanced Science and Biotechnology, Graduate
School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
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8
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Affiliation(s)
- M. C. R. Franssen
- Department of Organic Chemistry, Wageningen Agricultural University, Dreijenplein 8, 6703, HB, Wageningen, The Netherlands
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9
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Abstract
The wide media coverage given recently to a study correlating higher selenium levels with a reduced risk of advanced prostate cancer is but the latest addition to a growing body of epidemiological findings which link dietary selenium deficiency to diseases as diverse as cancer, heart disease, arthritis and AIDS. Indeed, selenium has a long history of association with human health and disease. Moreover, direct evidence is now emerging for specific beneficial effects of dietary selenium supplementation. Thus, the pharmacology, biology and biochemistry of selenium metabolism have become subjects of intense current interest. At the molecular level, selenium (as selenocysteine) is an essential component of the active sites of the enzymes glutathione peroxidase, iodothyronine 5'-deiodinase and mammalian thioredoxin reductase, and is also present in several other mammalian selenoproteins. Both glutathione peroxidase and thioredoxin reductase catalyse reactions essential to the protection of cellular components against oxidative and free radical damage. As a consequence of the growing recognition of the important biological role of selenium, a number of novel pharmaceutical agents, either selenium-based or which target specific aspects of selenium metabolism, are under development. Among these are orally active selenium-based antihypertensive agents, anticancer, antiviral, immunosuppressive and antimicrobial agents, and organoselenium compounds which reduce oxidative tissue damage and oedema. It can be anticipated that as our understanding of the basic biology and biochemistry of selenium increases, future efforts will uncover even more sophisticated approaches for the rational development of new selenium-based pharmaceutical agents.
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Affiliation(s)
- S W May
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
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10
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Casella L, Granata A, Monzani E, Pievo R, Pattarello L, Bubacco L. New aspects of the reactivity of tyrosinase. Micron 2004; 35:141-2. [PMID: 15036319 DOI: 10.1016/j.micron.2003.10.045] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Tyrosinase was found to be active in the sulfoxidation of thioanisol, producing the (R)-sulfoxide with high enantiomeric excess. The activity of the enzyme with phenolic and diphenolic substrates in a mixed aqueous Hepes buffer pH 6.8-methanol-glycerol solvent was also investigated over a range of temperatures. These experiments enabled us to deduce the thermodynamic parameters associated with substrate binding to the enzyme and the activation parameters associated with the rate determining step of the enzymatic reaction.
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Affiliation(s)
- Luigi Casella
- Dipartimento di Chimica Generale, Università di Pavia, Via Taramelli 12, 27100 Pavia, Italy.
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11
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Juliette LY, Hyman MR, Arp DJ. Inhibition of Ammonia Oxidation in
Nitrosomonas europaea
by Sulfur Compounds: Thioethers Are Oxidized to Sulfoxides by Ammonia Monooxygenase. Appl Environ Microbiol 1993; 59:3718-27. [PMID: 16349086 PMCID: PMC182523 DOI: 10.1128/aem.59.11.3718-3727.1993] [Citation(s) in RCA: 107] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Organic sulfur compounds are well-known nitrification inhibitors. The inhibitory effects of dimethylsulfide, dimethyldisulfide, and ethanethiol on ammonia oxidation by
Nitrosomonas europaea
were examined. Both dimethylsulfide and dimethyldisulfide were weak inhibitors of ammonia oxidation and exhibited inhibitory characteristics typical of substrates for ammonia monooxygenase (AMO). Depletion of dimethylsulfide required O
2
and was prevented with either acetylene or allylthiourea, two inhibitors of AMO. The inhibition of ammonia oxidation by dimethylsulfide was examined in detail. Cell suspensions incubated in the presence of ammonia oxidized dimethylsulfide to dimethyl sulfoxide. Depletion of six other thioethers was also prevented by treating cell suspensions with either allylthiourea or acetylene. The oxidative products of three thioethers were identified as the corresponding sulfoxides. The amount of sulfoxide formed accounted for a majority of the amount of sulfide depleted. By using gas chromatography coupled with mass spectrometry, allylmethylsulfide was shown to be oxidized to allylmethylsulfoxide by
N. europaea
with the incorporation of a single atom of
18
O derived from
18
O
2
into the sulfide. This result supported our conclusion that a monooxygenase was involved in the oxidation of allylmethylsulfide. The thioethers are concluded to be a new class of substrates for AMO. This is the first report of the oxidation of the sulfur atom by AMO in whole cells of
N. europaea
. The ability of
N. europaea
to oxidize dimethylsulfide is not unique among the ammonia-oxidizing bacteria.
Nitrosococcus oceanus
, a marine nitrifier, was also demonstrated to oxidize dimethylsulfide to dimethyl sulfoxide.
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Affiliation(s)
- L Y Juliette
- Laboratory for Nitrogen Fixation Research, Oregon State University, Corvallis, Oregon 97331-2902
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12
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Njus D, Kelley PM. The secretory-vesicle ascorbate-regenerating system: a chain of concerted H+/e(-)-transfer reactions. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1144:235-48. [PMID: 8399278 DOI: 10.1016/0005-2728(93)90108-r] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- D Njus
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202
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13
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14
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Debnath J, Husain PA, May SW. Activation of an adrenergic pro-drug through sequential stereoselective action of tandem target enzymes. Biochem Biophys Res Commun 1992; 189:33-9. [PMID: 1449487 DOI: 10.1016/0006-291x(92)91521-q] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The synthetic amino acid, 3,4-dihydroxyphenylserine (DOPS) has been of great interest for many years as an adrenergic pro-drug, since the L-threo diastereomer of DOPS can be a precursor of R-(-)-norepinephrine, the natural form of this neurotransmitter. We now report bioactivation of DOPS to the potent pharmacological agent, noradrenalone (arterenone), via sequential stereoselective action by two target enzymes--dopamine beta-monooxygenase (DBM) and L-aromatic amino acid decarboxylase (AADC)--acting in tandem. Enzymatic activation is stereospecific, with only the L-erythro DOPS diastereomer producing noradrenalone; this is consistent with the known stereospecificities of AADC and DBM. These results provide a heretofore unrecognized rationale for the bioactivity of L-erythro DOPS and provide a basis for the design of new adrenergic pro-drugs.
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Affiliation(s)
- J Debnath
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta 30332
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15
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Townes S, Titone C, Rosenberg RC. Inhibition of dopamine beta-hydroxylase by bidentate chelating agents. BIOCHIMICA ET BIOPHYSICA ACTA 1990; 1037:240-7. [PMID: 2306475 DOI: 10.1016/0167-4838(90)90174-e] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
1-2H-Phthalazine hydrazone (hydralazine; HYD), 2-1H-pyridinone hydrazone (2-hydrazinopyridine; HP), 2-quinoline-carboxylic acid (QCA), 1-isoquinolinecarboxylic acid (IQCA), 2,2'-bi-1H-imidazole (2,2'-biimidazole; BI), and 1H-imidazole-4-acetic acid (imidazole-4-acetic acid; IAA) directly and reversibly inhibit homogeneous soluble bovine dopamine beta-hydroxylase (3,4-dihydroxyphenethylamine, ascorbate:oxygen oxidoreductase (beta-hydroxylating), EC 1.14.17.1). HYD, QCA and IAA show competitive allosteric inhibition of dopamine beta-hydroxylase with respect to ascorbate (Kis = 5.7(+/- 0.9) microM, 0.14(+/- 0.03) mM, 0.80(+/- 0.20) mM; nH = 1.4(+/- 0.1), 1.8(+/- 0.4), 2.8(+/- 0.6), respectively). HYD and IAA show slope and intercept mixed-type allosteric inhibition of dopamine beta-hydroxylase with respect to tyramine. QCA shows allosteric uncompetitive inhibition of dopamine beta-hydroxylase with respect to tyramine. HP, BI and IQCA all show linear competitive inhibition (Kis = 1.9(+/- 0.3) microM, 21(+/- 6) microM, and 0.9(+/- 0.3) microM, respectively) with respect to ascorbate. HP and BI show linear mixed-type while IQCA shows linear uncompetitive inhibition of dopamine beta-hydroxylase with respect to tyramine. In the presence of HP, HYD or IAA intersecting double-reciprocal plots of the initial velocity as a function of tyramine concentration at differing fixed levels of ascorbate are observed. These findings are consistent with a uni-uni-ping-pong-ter-bi kinetic mechanism for dopamine beta-hydroxylase that involves a ternary enzyme-ascorbate-tyramine-oxygen complex. The results for HYD, QCA and IAA are the first examples of allosteric inhibitor interactions with dopamine beta-hydroxylase.
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Affiliation(s)
- S Townes
- Department of Chemistry, Howard University, Washington, DC 20059
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16
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Phillips RS, Fletcher JG, Von Tersch RL, Kirk KL. Oxygenation of fluorinated tyrosines by mushroom tyrosinase releases fluoride ion. Arch Biochem Biophys 1990; 276:65-9. [PMID: 2105082 DOI: 10.1016/0003-9861(90)90010-v] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The reactions of 2-fluoro- and 3-fluoro-L-tyrosine with mushroom tyrosinase have been investigated. Both fluorinated tyrosines are good substrates for tyrosinase, with Vmax and Vmax/Km values similar to those for L-tyrosine. Oxygenation of 2-fluorotyrosine is regioselective, and only 6-fluorodopa was detected by HPLC in reaction mixtures. Oxygenation of both isomers of monofluorotyrosine results in fluoride ion production in the absence of ascorbic acid; however, 2-fluorotyrosine also produces fluoride in the presence of ascorbic acid. These results are consistent with previous studies demonstrating rapid intramolecular cyclization of nascent 6-fluorodopaquinone (M.E. Rice, B. Moghaddan, C.R. Creveling, and K.L. Kirk, 1987, Anal. Chem. 59, 1534-1538), which is competitive with reduction by ascorbate, resulting in elimination of the aromatic fluorine as fluoride ion.
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Affiliation(s)
- R S Phillips
- Department of Chemistry, School of Chemical Sciences, University of Georgia, Athens 30602
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17
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DeWolf WE, Carr SA, Varrichio A, Goodhart PJ, Mentzer MA, Roberts GD, Southan C, Dolle RE, Kruse LI. Inactivation of dopamine beta-hydroxylase by p-cresol: isolation and characterization of covalently modified active site peptides. Biochemistry 1988; 27:9093-101. [PMID: 3242615 DOI: 10.1021/bi00426a005] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Recently, p-cresol has been shown to be a mechanism-based inhibitor of dopamine beta-hydroxylase (DBH; EC 1.14.17.1) [Goodhart, P. J., DeWolf, W. E., Jr., & Kruse, L. I. (1987) Biochemistry 26, 2576-2583]. This inactivation was suggested to result from alkylation of an active site residue by an aberrant 4-hydroxybenzyl radical intermediate. In support of this hypothesis, we report here the isolation and characterization of two modified tryptic peptides from DBH inactivated by p-cresol. Using a combination of automated Edman sequencing, mass spectroscopy (MS), and tandem MS, we have determined the sequence of the putative active site peptides, identified the site of attachment of p-cresol, and defined the chemical nature of the adduct formed. Both modified peptides are the same primary sequence: Ala-Pro-Asp-Val-Leu-Ile-Pro-Gly-Gln-Gln-Thr-Thr-Tyc-Trp-Cys-Tyr-Va l-Thr-Glu- Leu-Pro-Asp-Gly-Phe-Pro-Arg, where Tyc is an amino acid residue with the in-chain mass of a cresol-Tyr adduct (106 + 163 Da). Gas-phase deuterium exchange studies (employing N2H3-DCI MS) of the isolated phenylthiohydantoin (Pth) derivatives of modified residue 13 demonstrate that p-cresol forms two chemically distinct covalent adducts and support the hypothesis that a (4-hydroxyphenyl)methyl radical is generated during catalysis. Rearrangement to a (4-methylphenyl)oxy radical may also occur prior to inactivation.
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Affiliation(s)
- W E DeWolf
- Department of Medicinal Chemistry, Smith Kline & French Laboratories, King of Prussia, Pennsylvania 19406
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19
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Herman HH, Wimalasena K, Fowler LC, Beard CA, May SW. Demonstration of the ascorbate dependence of membrane-bound dopamine beta-monooxygenase in adrenal chromaffin granule ghosts. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(19)35404-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
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20
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Abstract
The copper-containing monooxygenase dopamine beta-hydroxylase catalyzes the hydroxylation of dopamine at the benzylic position to form norepinephrine. Mechanism-based inhibitors for dopamine beta-hydroxylase have been used as probes of the mechanism of catalysis. The variety of such inhibitors that have been developed for this enzyme can be divided into three groups: (i) those in which the inactivating species is formed by abstraction of a hydrogen atom to form a radical intermediate; (ii) those in which the inactivating species is formed by abstraction of an electron to form an epoxide-like intermediate; and (iii) those in which the product is the inactivating species. A mechanism consistent with inactivation by all three groups of inhibitors which proposes that hydroxylation of dopamine by dopamine beta-hydroxylase involves formation of a benzylic radical has been developed. The benzylic radical is formed by abstraction of a hydrogen atom from the substrate by a high-potential copper-oxygen species.
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Affiliation(s)
- P F Fitzpatrick
- Department of Biochemistry and Biophysics, Texas A&M University, College Station
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21
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May SW, Herman HH, Roberts SF, Ciccarello MC. Ascorbate depletion as a consequence of product recycling during dopamine beta-monooxygenase catalyzed selenoxidation. Biochemistry 1987; 26:1626-33. [PMID: 3036204 DOI: 10.1021/bi00380a021] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The competence of dopamine beta-monooxygenase (DBM) to process selenide substrates was investigated, in anticipation that the expected selenoxide products would exhibit unique reactivity and redox properties. The prototypical selenide phenyl 2-aminoethyl selenide (PAESe) was synthesized and shown to be a substrate for DBM with the characteristic e/O2 ratio of 2:1 for monooxygenation. The kinetic parameters for oxygenation of PAESe were found to be similar to those for the DBM-catalyzed sulfoxidation of the cognate sulfide phenyl 2-aminoethyl sulfide [May, S. W., & Phillips, R. S. (1980) J. Am. Chem. Soc. 102, 5981-5983], and selenoxidation was stimulated by fumarate in a manner similar to other well-characterized DBM monooxygenation reactions. Identification of phenyl 2-aminoethyl selenoxide (PAESeO) as the enzymatic product was accomplished by the demonstration of coincident elution of authentic PAESeO with the enzymatic product in three significantly different HPLC systems. PAESeO was found to oxidize ascorbic acid with the concomitant and stoichiometric reduction of PAESeO back to the selenide, PAESe. As a consequence of this nonenzymatic reaction, ascorbate-supported DBM turnover was prematurely terminated under standard assay conditions due to depletion of reduced ascorbate. The kinetics of the redox reaction between PAESeO and ascorbate were investigated with a spectrophotometric assay of ascorbate at 300 nm, and a second-order rate constant of 3.4 M-1 s-1 was determined at pH 5.0, 25 degrees C. Spectrophotometric assay of cytochrome c (cyt c) reduction at 550 nm during the oxidation of ascorbate by PAESeO demonstrated that no cyt c trappable semidehydroascorbate was produced in this nonenzymatic reaction.(ABSTRACT TRUNCATED AT 250 WORDS)
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22
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May SW, Katopodis AG. Oxygenation of alcohol and sulphide substrates by a prototypical non-haem iron monooxygenase: catalysis and biotechnological potential. Enzyme Microb Technol 1986. [DOI: 10.1016/0141-0229(86)90004-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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23
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Padgette SR, Wimalasena K, Herman HH, Sirimanne SR, May SW. Olefin oxygenation and N-dealkylation by dopamine beta-monooxygenase: catalysis and mechanism-based inhibition. Biochemistry 1985; 24:5826-39. [PMID: 4084493 DOI: 10.1021/bi00342a021] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In an initial communication [May, S. W., Mueller, P. W., Padgette, S. R., Herman, H. H., & Phillips, R. S. (1983) Biochem. Biophys. Res. Commun. 110, 161-168], we reported that 1-phenyl-1-(aminomethyl)ethene hydrochloride (PAME) is an olefinic substrate for dopamine beta-monooxygenase (DBM; EC 1.14.17.1) which inactivates the enzyme in an apparent mechanism-based manner. The present study further characterizes this reaction. The inactivation reaction yields kinact = 0.23 min-1 at pH 5.0 and 37 degrees C and is strictly dependent on reductant (ascorbate) and oxygen. The DBM/PAME substrate reaction (apparent kcat = 14 s-1), shown to be stimulated by fumarate, gives the corresponding epoxide as product, identified by derivatization with 4-(p-nitrobenzyl)pyridine. However, the lack of DBM inhibition by alpha-methylstyrene oxide, and the observation of identical PAME/DBM inactivation rates in the absence and presence of preformed enzymatic PAME epoxide, indicates that free epoxide is not the inactivating species. A structure-activity study revealed that 4-hydroxylation of PAME (to give 4-HOPAME) increases both kinact (0.81 min-1) and apparent kcat (56 s-1) values, while 3-hydroxylation (to give 3-HOPAME) greatly diminishes inactivation activity while retaining substrate activity (apparent kcat = 47 s-1). 4-Hydroxy-alpha-methylstyrene was found to be a DBM inhibitor (kinact = 0.53 min-1) with weak substrate activity (apparent kcat = 0.71 s-1), while 3-hydroxy-alpha-methylstyrene and alpha-(cyanomethyl) styrene were found not to exhibit detectable DBM substrate activity and only weak inhibitory activity. 3-Phenylpropargylamine hydrochloride showed no detectable DBM substrate activity but rapidly inactivated the enzyme. A new substrate activity for DBM was discovered, N-dealkylation of N-phenylethylenediamine and N-methyl-N-phenylethylenediamine, and the lack of O-dealkylation activity with phenyl 2-aminoethyl ether and 4-hydroxyphenyl 2-aminoethyl ether indicates that DBM N-dealkylation proceeds via initial one-electron abstraction from the benzylic nitrogen heteroatom. With this new substrate and inhibitor reactivity information in hand, along with the other known substrate reactions, a DBM oxygenation mechanism analogous to that for cytochrome P-450 is proposed.
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Ash DE, Papadopoulos NJ, Colombo G, Villafranca JJ. Kinetic and spectroscopic studies of the interaction of copper with dopamine beta-hydroxylase. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43105-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Colombo G, Rajashekhar B, Ash DE, Villafranca JJ. Alternate substrates of dopamine beta-hydroxylase. III. Stoichiometry of the inactivation reaction with benzyl cyanides and spectroscopic investigations. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43452-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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Colombo G, Giedroc DP, Rajashekhar B, Villafranca JJ. Alternate substrates of dopamine beta-hydroxylase. II. Inhibition by benzyl cyanides and reactivation of inhibited enzyme. J Biol Chem 1984. [DOI: 10.1016/s0021-9258(17)43451-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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May SW, Padgette SR. Oxidoreductase Enzymes in Biotechnology: Current Status and Future Potential. Nat Biotechnol 1983. [DOI: 10.1038/nbt1083-677] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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May SW, Mueller PW, Padgette SR, Herman HH, Phillips RS. Dopamine-B-hydroxylase: suicide inhibition by the novel olefinic substrate, 1-phenyl-1-aminomethylethene. Biochem Biophys Res Commun 1983; 110:161-8. [PMID: 6860408 DOI: 10.1016/0006-291x(83)91274-3] [Citation(s) in RCA: 31] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Dopamine-B-hydroxylase [E.C.1.14.17.1] plays a key role in the biosynthetic interconversion of neurotransmitters. It is now demonstrated for the first time that dopamine-B-hydroxylase also catalyzes the oxygenation of an olefinic substrate, 1-phenyl-1-aminomethylethene, producing 2,3-dihydroxy-2-phenylpropylamine after acid workup. This reaction gives the normal oxygenase stoichiometry of electrons to O2 to product of 2:1:1, and is kinetically comparable to other oxygenase activities of dopamine-B-hydroxylase, with a kcat value of 10 sec-1 and a KM of 8.3 mM. 1-Phenyl-1-aminomethylethene is also a time-dependent, first-order inactivator of dopamine-B-hydroxylase. The inactivation process exhibits the characteristics of mechanism-based, irreversible inactivation, giving a KI value of 13 mM and a kinac of 0.04 min-1. The central role of dopamine-B-hydroxylase in catecholamine metabolism suggests possible pharmacological uses for olefinic inhibitors of this enzyme.
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May SW, Phillips RS, Herman HH, Mueller PW. Bioactivation of Catha edulis alkaloids: enzymatic ketonization of norpseudoephedrine. Biochem Biophys Res Commun 1982; 104:38-44. [PMID: 7073680 DOI: 10.1016/0006-291x(82)91937-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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A model for fad-containing monooxygenas: the oxidation of thioanisole derivatives by an isoalloxazine hydroperoxide. Tetrahedron Lett 1982. [DOI: 10.1016/s0040-4039(00)86939-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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