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Feng J, Jin R, Cheng S, Li H, Wang X, Chen K. Establishing an Artificial Pathway for the Biosynthesis of Octopamine and Synephrine. ACS Synth Biol 2024; 13:1762-1772. [PMID: 38815614 DOI: 10.1021/acssynbio.4c00082] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2024]
Abstract
In this study, we designed an artificial pathway composed of tyramine β-hydroxylase (TBH) and phenylethanolamine N-methyltransferase (PNMT) for the biosynthesis of both octopamine and synephrine. As most TBH and PNMT originate from eukaryotic animals and plants, the heterologous expression and identification of functional TBH and PNMT are critical for establishing the pathway in mode microorganisms like Escherichia coli. Here, three TBHs were evaluated, and only TBH from Drosophila melanogaster was successfully expressed in the soluble form in E. coli. Its expression was promoted by evaluating the effects of different expression strategies. The specific enzyme activity of TBH was optimized up to 229.50 U·g-1, and the first step in the biosynthetic pathway was successfully established and converted tyramine to synthesize 0.10 g/L of octopamine. Furthermore, the second step to produce synephrine from octopamine was developed by screening PNMT, enhancing enzyme activity, and optimizing reaction conditions, with a maximum synephrine production of 2.02 g/L. Finally, based on the optimization of the reaction conditions for each individual reaction, the one-pot cascade reaction for synthesizing synephrine from tyramine was constructed by combining the TBH and PNMT. The synthetic synephrine reached 30.05 mg/L with tyramine as substrate in the two-step enzyme cascade system. With further optimization and amplification, the titers of octopamine and synephrine were increased to 0.45 and 0.20 g/L, respectively, with tyramine as substrate. This work was the first achievement of the biosynthesis of octopamine and synephrine to date.
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Affiliation(s)
- Jiao Feng
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Runyuan Jin
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Shasha Cheng
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Hui Li
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Xin Wang
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China
| | - Kequan Chen
- State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, Nanjing 211816, People's Republic of China
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2
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Theoretical perspective on mononuclear copper-oxygen mediated C–H and O–H activations: A comparison between biological and synthetic systems. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(21)63974-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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3
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Affiliation(s)
- Judith Münch
- Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120, Halle, Saale, Germany
| | - Pascal Püllmann
- Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120, Halle, Saale, Germany
| | - Wuyuan Zhang
- Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, 32 West seventh Avenue, Tianjin 300308, China
- National Technology Innovation Center of Synthetic Biology, 32 West seventh Avenue, Tianjin 300308, China
| | - Martin J. Weissenborn
- Leibniz Institute of Plant Biochemistry, Weinberg 3, 06120, Halle, Saale, Germany
- Institute of Chemistry, MartinLuther-University Halle-Wittenberg, Kurt-Mothes-Strasse 2, 06120, Halle, Saale, Germany
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4
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Wu P, Fan F, Song J, Peng W, Liu J, Li C, Cao Z, Wang B. Theory Demonstrated a "Coupled" Mechanism for O 2 Activation and Substrate Hydroxylation by Binuclear Copper Monooxygenases. J Am Chem Soc 2019; 141:19776-19789. [PMID: 31746191 DOI: 10.1021/jacs.9b09172] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Multiscale simulations have been performed to address the longstanding issue of "dioxygen activation" by the binuclear copper monooxygenases (PHM and DβM), which have been traditionally classified as "noncoupled" binuclear copper enzymes. Our QM/MM calculations rule out that CuM(II)-O2• is an active species for H-abstraction from the substrate. In contrast, CuM(II)-O2• would abstract an H atom from the cosubstrate ascorbate to form a CuM(II)-OOH intermediate in PHM and DβM. Consistent with the recently reported structural features of DβM, the umbrella sampling shows that the "open" conformation of the CuM(II)-OOH intermediate could readily transform into the "closed" conformation in PHM, in which we located a mixed-valent μ-hydroperoxodicopper(I,II) intermediate, (μ-OOH)Cu(I)Cu(II). The subsequent O-O cleavage and OH moiety migration to CuH generate the unexpected species (μ-O•)(μ-OH)Cu(II)Cu(II), which is revealed to be the reactive intermediate responsible for substrate hydroxylation. We also demonstrate that the flexible Met ligand is favorable for O-O cleavage reactions, while the replacement of Met with the strongly bound His ligand would inhibit the O-O cleavage reactivity. As such, the study not only demonstrates a "coupled" mechanism for O2 activation by binuclear copper monooxygenases but also deciphers the full catalytic cycle of PHM and DβM in accord with the available experimental data. These findings of O2 activation and substrate hydroxylation by binuclear copper monooxygenases could expand our understanding of the reactivities of the synthetic monocopper complexes.
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Affiliation(s)
- Peng Wu
- State Key Laboratory of Structural Chemistry , Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou , Fujian 350002 , People's Republic of China.,University of Chinese Academy of Sciences , Beijing 100049 , People's Republic of China
| | - Fangfang Fan
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 360015 , People's Republic of China
| | - Jinshuai Song
- College of Chemistry, and Institute of Green Catalysis , Zhengzhou University , Zhengzhou 450001 , People's Republic of China
| | - Wei Peng
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 360015 , People's Republic of China
| | - Jia Liu
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 360015 , People's Republic of China
| | - Chunsen Li
- State Key Laboratory of Structural Chemistry , Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences , Fuzhou , Fujian 350002 , People's Republic of China.,Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry , Xiamen , Fujian 361005 , People's Republic of China
| | - Zexing Cao
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 360015 , People's Republic of China
| | - Binju Wang
- State Key Laboratory of Physical Chemistry of Solid Surfaces and Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering , Xiamen University , Xiamen 360015 , People's Republic of China
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5
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Preza M, Montagne J, Costábile A, Iriarte A, Castillo E, Koziol U. Analysis of classical neurotransmitter markers in tapeworms: Evidence for extensive loss of neurotransmitter pathways. Int J Parasitol 2018; 48:979-992. [DOI: 10.1016/j.ijpara.2018.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Revised: 05/30/2018] [Accepted: 06/06/2018] [Indexed: 12/28/2022]
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6
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Vendelboe TV, Harris P, Zhao Y, Walter TS, Harlos K, El Omari K, Christensen HEM. The crystal structure of human dopamine β-hydroxylase at 2.9 Å resolution. SCIENCE ADVANCES 2016; 2:e1500980. [PMID: 27152332 PMCID: PMC4846438 DOI: 10.1126/sciadv.1500980] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Accepted: 03/06/2016] [Indexed: 05/23/2023]
Abstract
The norepinephrine pathway is believed to modulate behavioral and physiological processes, such as mood, overall arousal, and attention. Furthermore, abnormalities in the pathway have been linked to numerous diseases, for example hypertension, depression, anxiety, Parkinson's disease, schizophrenia, Alzheimer's disease, attention deficit hyperactivity disorder, and cocaine dependence. We report the crystal structure of human dopamine β-hydroxylase, which is the enzyme converting dopamine to norepinephrine. The structure of the DOMON (dopamine β-monooxygenase N-terminal) domain, also found in >1600 other proteins, reveals a possible metal-binding site and a ligand-binding pocket. The catalytic core structure shows two different conformations: an open active site, as also seen in another member of this enzyme family [the peptidylglycine α-hydroxylating (and α-amidating) monooxygenase], and a closed active site structure, in which the two copper-binding sites are only 4 to 5 Å apart, in what might be a coupled binuclear copper site. The dimerization domain adopts a conformation that bears no resemblance to any other known protein structure. The structure provides new molecular insights into the numerous devastating disorders of both physiological and neurological origins associated with the dopamine system.
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Affiliation(s)
- Trine V. Vendelboe
- Department of Chemistry, Kemitorvet 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Pernille Harris
- Department of Chemistry, Kemitorvet 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
| | - Yuguang Zhao
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Thomas S. Walter
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Karl Harlos
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Kamel El Omari
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Hans E. M. Christensen
- Department of Chemistry, Kemitorvet 207, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark
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7
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Zhu H, Sommerhalter M, Nguy AKL, Klinman JP. Solvent and Temperature Probes of the Long-Range Electron-Transfer Step in Tyramine β-Monooxygenase: Demonstration of a Long-Range Proton-Coupled Electron-Transfer Mechanism. J Am Chem Soc 2015; 137:5720-9. [PMID: 25919134 PMCID: PMC4970857 DOI: 10.1021/ja512388n] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
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Tyramine
β-monooxygenase (TβM) belongs to a family
of physiologically important dinuclear copper monooxygenases that
function with a solvent-exposed active site. To accomplish each enzymatic
turnover, an electron transfer (ET) must occur between two solvent-separated
copper centers. In wild-type TβM, this event is too fast to
be rate limiting. However, we have recently shown [Osborne, R. L.;
et al. Biochemistry2013, 52, 1179] that the Tyr216Ala variant of TβM leads to rate-limiting
ET. In this study, we present a pH–rate profile study of Tyr216Ala,
together with deuterium oxide solvent kinetic isotope effects (KIEs).
A solvent KIE of 2 on kcat is found in
a region where kcat is pH/pD independent.
As a control, the variant Tyr216Trp, for which ET is not rate determining,
displays a solvent KIE of unity. We conclude, therefore, that the
observed solvent KIE arises from the rate-limiting ET step in the
Tyr216Ala variant, and show
how small solvent KIEs (ca. 2) can be fully accommodated from equilibrium effects within the Marcus equation. To gain insight into the role of the enzyme in the long-range
ET step, a temperature dependence study was also pursued. The small
enthalpic barrier of ET (Ea = 3.6 kcal/mol)
implicates a significant entropic barrier, which is attributed to
the requirement for extensive rearrangement of the inter-copper environment
during PCET catalyzed by the Tyr216Ala variant. The data lead to the
proposal of a distinct inter-domain pathway for PCET in the dinuclear
copper monooxygenases.
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Affiliation(s)
| | - Monika Sommerhalter
- #Department of Chemistry and Biochemistry, California State University, East Bay, 25800 Carlos Bee Boulevard, Hayward, California 94542, United States
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8
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Dempsey DR, Jeffries KA, Bond JD, Carpenter AM, Rodriguez-Ospina S, Breydo L, Caswell KK, Merkler DJ. Mechanistic and structural analysis of Drosophila melanogaster arylalkylamine N-acetyltransferases. Biochemistry 2014; 53:7777-93. [PMID: 25406072 PMCID: PMC4270386 DOI: 10.1021/bi5006078] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
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Arylalkylamine N-acetyltransferase (AANAT) catalyzes the penultimate step in the
biosynthesis of melatonin and other N-acetylarylalkylamides
from the corresponding arylalkylamine and acetyl-CoA. The N-acetylation
of arylalkylamines is a critical step in Drosophila melanogaster for the inactivation of the bioactive amines and the sclerotization
of the cuticle. Two AANAT variants (AANATA and AANATB) have been identified
in D. melanogaster, in which AANATA differs from
AANATB by the truncation of 35 amino acids from the N-terminus. We
have expressed and purified both D. melanogaster AANAT
variants (AANATA and AANATB) in Escherichia coli and
used the purified enzymes to demonstrate that this N-terminal truncation
does not affect the activity of the enzyme. Subsequent characterization
of the kinetic and chemical mechanism of AANATA identified an ordered
sequential mechanism, with acetyl-CoA binding first, followed by tyramine.
We used a combination of pH–activity profiling and site-directed
mutagenesis to study prospective residues believed to function in
AANATA catalysis. These data led to an assignment of Glu-47 as the
general base in catalysis with an apparent pKa of 7.0. Using the data generated for the kinetic mechanism,
structure–function relationships, pH–rate profiles,
and site-directed mutagenesis, we propose a chemical mechanism for
AANATA.
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Affiliation(s)
- Daniel R Dempsey
- Department of Chemistry, University of South Florida , Tampa, Florida 33620, United States
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9
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Solomon EI, Heppner DE, Johnston EM, Ginsbach JW, Cirera J, Qayyum M, Kieber-Emmons MT, Kjaergaard CH, Hadt RG, Tian L. Copper active sites in biology. Chem Rev 2014; 114:3659-853. [PMID: 24588098 PMCID: PMC4040215 DOI: 10.1021/cr400327t] [Citation(s) in RCA: 1133] [Impact Index Per Article: 113.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
| | - David E. Heppner
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | - Jake W. Ginsbach
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Jordi Cirera
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Munzarin Qayyum
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | | | | | - Ryan G. Hadt
- Department of Chemistry, Stanford University, Stanford, CA, 94305
| | - Li Tian
- Department of Chemistry, Stanford University, Stanford, CA, 94305
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10
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Osborne RL, Zhu H, Iavarone AT, Blackburn NJ, Klinman JP. Interdomain long-range electron transfer becomes rate-limiting in the Y216A variant of tyramine β-monooxygenase. Biochemistry 2013; 52:1179-91. [PMID: 23320946 DOI: 10.1021/bi3013609] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The enzyme tyramine β-monooxygenase (TβM) belongs to a small eukaryotic family of physiologically important mononuclear dicopper monooxygenases. The properties of this family include noncoupled mononuclear copper centers ~11 Å apart, with Cu(M) performing C-H and O(2) activation and Cu(H) functioning as an electron storage site [Klinman, J. P. (2006) J. Biol. Chem. 281, 3013-3016]. A conserved tyrosine (Y216 in TβM) is positioned between the copper domains and is associated with Cu(H) (through an interaction with a Cu(H)-coordinating histidine). Mutations at Y216 (to W, I, and A) indicate little or no difference in electron paramagnetic resonance spectra, while X-ray absorption spectroscopy studies show only a very small decrease in distance between Cu(M) and its Met471 ligand in reduced enzyme. High-performance liquid chromatography assays demonstrate that turnover of substrate is complete with Y216W and Y216I, whereas Y216A undergoes a secondary inactivation that is linked to oxidation of ligands at Cu(M). Steady-state kinetic and isotope effect measurements were investigated. The significantly elevated K(m,Tyr) for Y216A, together with a very large (D)(k(cat)/K(m,Tyr)) of ~12, indicates a major impact on the binding of substrate at the Cu(M) site. The kinetic and isotopic parameters lead to estimated rate constants for C-H bond cleavage, dissociation of substrate from the Cu(M) site, and, in the case of Y216A, the rate of electron transfer (ET) from Cu(H) to Cu(M). These studies uncover a rate-limiting ET within the solvent-filled interface and lead to a paradigm shift in our understanding of the mononuclear dicopper monooxygenases.
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Affiliation(s)
- Robert L Osborne
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
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Osborne RL, Zhu H, Iavarone AT, Hess CR, Klinman JP. Inactivation of Met471Cys tyramine β-monooxygenase results from site-specific cysteic acid formation. Biochemistry 2012; 51:7488-95. [PMID: 22891760 PMCID: PMC3567250 DOI: 10.1021/bi300456f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tyramine β-monooxygenase (TβM), the insect homologue of dopamine β-monooxygenase, is a neuroregulatory enzyme that catalyzes the β-hydroxylation of tyramine to yield octopamine. Mutation of the methionine (Met) ligand to Cu(M) of TβM, Met471Cys, yielded a form of TβM that is catalytically active but susceptible to inactivation during turnover [Hess, C. R., Wu, Z., Ng, A., Gray, E. E., McGuirl, M. M., and Klinman, J. P. (2008) J. Am. Chem. Soc. 130, 11939-11944]. Further, although the wild-type (WT) enzyme undergoes coordination of Met471 to Cu(M) in its reduced form, the generation of Met471Cys almost completely eliminates this interaction [Hess, C. R., Klinman, J. P., and Blackburn, N. J. (2010) J. Biol. Inorg. Chem. 15, 1195-1207]. The aim of this study is to identify the chemical consequence of the poor ability of Cys to coordinate Cu(M). We show that Met471Cys TβM is ~5-fold more susceptible to inactivation than the WT enzyme in the presence of the cosubstrate/reductant ascorbate and that this process is not facilitated by the substrate tyramine. The resulting 50-fold smaller ratio for turnover to inactivation in the case of Met471Cys prevents full turnover of the substrate under all conditions examined. Liquid chromatography-tandem mass spectrometry analysis of proteolytic digests of inactivated Met471Cys TβM leads to the identification of cysteic acid at position 471. While both Met and Cys side chains are expected to be similarly subject to oxidative damage in proteins, the enhanced reactivity of Met471Cys toward solution oxidants in TβM is attributed to its weaker interaction with Cu(I)(M).
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Affiliation(s)
- Robert L. Osborne
- Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Hui Zhu
- Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Anthony T. Iavarone
- Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Corinna R. Hess
- Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
| | - Judith P. Klinman
- Department of Chemistry, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
- Department of Molecular and Cell Biology, and the California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, CA 94720, USA
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12
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De La Lande A, Salahub DR, Maddaluno J, Scemama A, Pilme J, Parisel O, Gerard H, Caffarel M, Piquemal JP. Spin-driven activation of dioxygen in various metalloenzymes and their inspired models. J Comput Chem 2010; 32:1178-82. [DOI: 10.1002/jcc.21698] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 08/25/2010] [Accepted: 09/13/2010] [Indexed: 12/19/2022]
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13
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The copper centers of tyramine β-monooxygenase and its catalytic-site methionine variants: an X-ray absorption study. J Biol Inorg Chem 2010; 15:1195-207. [PMID: 20544364 PMCID: PMC2988203 DOI: 10.1007/s00775-010-0677-3] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 05/12/2010] [Indexed: 10/31/2022]
Abstract
Tyramine β-monooxygenase (TBM) is a member of a family of copper monooxygenases containing two noncoupled copper centers, and includes peptidylglycine monooxygenase and dopamine β-monooxygenase. In its Cu(II) form, TBM is coordinated by two to three His residues and one to two non-His O/N ligands consistent with a [Cu(M)(His)(2)(OH(2))(2)-Cu(H)(His)(3)(OH(2))] formulation. Reduction to the Cu(I) state causes a change in the X-ray absorption spectroscopy (XAS) spectrum, consistent with a change to a [Cu(M)(His)(2)S(Met)-Cu(H)(His)(3)] environment. Lowering the pH to 4.0 results in a large increase in the intensity of the Cu(I)-S extended X-ray absorption fine structure (EXAFS) component, suggesting a tighter Cu-S bond or the coordination of an additional sulfur donor. The XAS spectra of three variants, where the Cu(M) Met471 residue had been mutated to His, Cys, and Asp, were examined. Significant differences from the wild-type enzyme are evident in the spectra of the reduced mutants. Although the side chains of His, Cys, and Asp are expected to substitute for Met at the Cu(M) site, the data showed identical spectra for all three reduced variants, with no evidence for coordination of residue 471. Rather, the K-edge data suggested a modest decrease in coordination number, whereas the EXAFS indicated an average of two His residues at each Cu(I) center. These data highlight the unique role of the Met residue at the Cu(M) center, and pose interesting questions as to why replacement by the cuprophilic thiolate ligand leads to detectable activity whereas replacement by imidazole generates inactive TBM.
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14
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Hess CR, Wu Z, Ng A, Gray EE, McGuirl MA, Klinman JP. Hydroxylase activity of Met471Cys tyramine beta-monooxygenase. J Am Chem Soc 2008; 130:11939-44. [PMID: 18710228 DOI: 10.1021/ja800408h] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
A series of mutations was targeted at the methionine residue, Met471, coordinating the Cu(M) site of tyramine beta-monooxygenase (TbetaM). The methionine ligand at Cu(M) is believed to be key to dioxygen activation and the hydroxylation chemistry of the copper monooxygenases. The reactivity and copper binding properties of three TbetaM mutants, Met471Asp, Met471Cys, and Met471His, were examined. All three mutants show similar metal binding affinities to wild type TbetaM in the oxidized enzyme forms. EPR spectroscopy suggests that the Cu(II) coordination geometry is identical to that of the WT enzyme. However, substrate hydroxylation was observed for the reaction of tyramine solely with Met471Cys TbetaM. Met471Cys TbetaM provides the first example of an active mutant directed at the Cu(M) site of this class of hydroxylases. The reactivity and altered kinetics of the Met471Cys mutant further highlight the central role of the methionine residue in the enzyme mechanism. The sole ability of the cysteine residue to support activity among the series of alternate amino acids investigated is relevant to theoretical and biomimetic investigations of dioxygen activation at mononuclear copper centers.
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Affiliation(s)
- Corinna R Hess
- Department of Chemistry, University of California, Berkeley, California 94720-3220, USA
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15
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Hess CR, McGuirl MM, Klinman JP. Mechanism of the insect enzyme, tyramine beta-monooxygenase, reveals differences from the mammalian enzyme, dopamine beta-monooxygenase. J Biol Chem 2007; 283:3042-3049. [PMID: 18032384 DOI: 10.1074/jbc.m705911200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Tyramine beta-monooxygenase (TbetaM) catalyzes the synthesis of the neurotransmitter, octopamine, in insects. Kinetic and isotope effect studies have been carried out to determine the kinetic mechanism of TbetaM for comparison with the homologous mammalian enzymes, dopamine beta-monooxygenase and peptidylglycine alpha-hydroxylating monooxygenase. A new and distinctive feature of TbetaM is very strong substrate inhibition that is dependent on the level of the co-substrate, O(2), and reductant as well as substrate deuteration. This has led to a model in which tyramine can bind to either the Cu(I) or Cu(II) forms of TbetaM, with substrate inhibition ameliorated at very high ascorbate levels. The rate of ascorbate reduction of the E-Cu(II) form of TbetaM is also reduced at high tyramine, leading us to propose the existence of a binding site for ascorbate to this class of enzymes. These findings may be relevant to the control of octopamine production in insect cells.
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Affiliation(s)
- Corinna R Hess
- Department of Chemistry , University of California, Berkeley, California 94720
| | - Michele M McGuirl
- Division of Biological Sciences and the Biomolecular Structure and Dynamics Program, University of Montana, Missoula, Montana 59812
| | - Judith P Klinman
- Department of Chemistry , University of California, Berkeley, California 94720; Molecular and Cell Biology, University of California, Berkeley, California 94720.
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