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Hong H, Lee UJ, Lee SH, Kim H, Lim GM, Lee SH, Son HF, Kim BG, Kim KJ. Highly efficient site-specific protein modification using tyrosinase from Streptomyces avermitilis: Structural insight. Int J Biol Macromol 2024; 255:128313. [PMID: 37995783 DOI: 10.1016/j.ijbiomac.2023.128313] [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] [Received: 08/15/2023] [Revised: 11/19/2023] [Accepted: 11/19/2023] [Indexed: 11/25/2023]
Abstract
Tyrosinase-mediated protein conjugation has recently drawn attention as a site-specific protein modification tool under mild conditions. However, the tyrosinases reported to date act only on extremely exposed tyrosine residues, which limits where the target tyrosine can be located. Herein, we report a tyrosinase from Streptomyces avermitilis (SaTYR), that exhibits a much higher activity against tyrosine residues on the protein surface than other tyrosinases. We determined the crystal structure of SaTYR and revealed that the enzyme has a relatively flat and shallow substrate-binding pocket to accommodate a protein substrate. We demonstrated SaTYR-mediated fluorescence dye tagging and PEGylation of a surface tyrosine residue that was unreacted by other tyrosinases with an approximately 95.2 % conjugation yield in 1 h. We also present a structural rationale that considers the steric hindrance from adjacent residues and surrounding structures along with the extent of solvent exposure of residues, as necessary when determining the optimal positions for introducing target tyrosine residues in SaTYR-mediated protein modification. The study demonstrated that the novel tyrosinase, SaTYR, extends the scope of tyrosinase-mediated protein modification, and we propose that site-specific tyrosine conjugation using SaTYR is a promising strategy for protein bioconjugation in various applications.
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Affiliation(s)
- Hwaseok Hong
- School of Life Sciences, BK21 FOUR KNU Creative BioResearch Group, KNU Institute of Microbiology, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Uk-Jae Lee
- School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea; Bio-MAX/N-Bio, Institute of BioEngineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Seul Hoo Lee
- School of Life Sciences, BK21 FOUR KNU Creative BioResearch Group, KNU Institute of Microbiology, Kyungpook National University, Daegu 41566, Republic of Korea
| | - Hyun Kim
- School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea; Bio-MAX/N-Bio, Institute of BioEngineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Gyu-Min Lim
- Interdisciplinary Program for Biochemical Engineering and Biotechnology, Seoul National University, Seoul 08826, Republic of Korea
| | - Sang-Hyuk Lee
- Interdisciplinary Program for Biochemical Engineering and Biotechnology, Seoul National University, Seoul 08826, Republic of Korea
| | - Hyeoncheol Francis Son
- Clean Energy Research Center, Korea Institute of Science and Technology, Seoul, Republic of Korea
| | - Byung-Gee Kim
- School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea; Bio-MAX/N-Bio, Institute of BioEngineering, Seoul National University, Seoul 08826, Republic of Korea; Interdisciplinary Program for Biochemical Engineering and Biotechnology, Seoul National University, Seoul 08826, Republic of Korea.
| | - Kyung-Jin Kim
- School of Life Sciences, BK21 FOUR KNU Creative BioResearch Group, KNU Institute of Microbiology, Kyungpook National University, Daegu 41566, Republic of Korea.
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Kipouros I, Solomon EI. New mechanistic insights into coupled binuclear copper monooxygenases from the recent elucidation of the ternary intermediate of tyrosinase. FEBS Lett 2023; 597:65-78. [PMID: 36178078 PMCID: PMC9839588 DOI: 10.1002/1873-3468.14503] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 09/16/2022] [Accepted: 09/20/2022] [Indexed: 01/17/2023]
Abstract
Tyrosinase is the most predominant member of the coupled binuclear copper (CBC) protein family. The recent trapping and spectroscopic definition of the elusive catalytic ternary intermediate (enzyme/O2 /monophenol) of tyrosinase dictates a monooxygenation mechanism that revises previous proposals and involves cleavage of the μ-η2 :η2 -peroxide dicopper(II) O-O bond to accept the phenolic proton, followed by monophenolate coordination to copper concomitant with aromatic hydroxylation by the non-protonated μ-oxo. Here, we compare and contrast previously proposed and current mechanistic models for monophenol monooxygenation of tyrosinase. Next, we discuss how these recent insights provide new opportunities towards uncovering structure-function relationships in CBC enzymes, as well as understanding fundamental principles for O2 activation and reactivity by bioinorganic active sites.
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Affiliation(s)
| | - Edward I Solomon
- Department of Chemistry, Stanford University, CA, USA
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, CA, USA
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Panis F, Rompel A. The Novel Role of Tyrosinase Enzymes in the Storage of Globally Significant Amounts of Carbon in Wetland Ecosystems. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:11952-11968. [PMID: 35944157 PMCID: PMC9454253 DOI: 10.1021/acs.est.2c03770] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2022] [Revised: 07/01/2022] [Accepted: 07/05/2022] [Indexed: 05/30/2023]
Abstract
Over the last millennia, wetlands have been sequestering carbon from the atmosphere via photosynthesis at a higher rate than releasing it and, therefore, have globally accumulated 550 × 1015 g of carbon, which is equivalent to 73% of the atmospheric carbon pool. The accumulation of organic carbon in wetlands is effectuated by phenolic compounds, which suppress the degradation of soil organic matter by inhibiting the activity of organic-matter-degrading enzymes. The enzymatic removal of phenolic compounds by bacterial tyrosinases has historically been blocked by anoxic conditions in wetland soils, resulting from waterlogging. Bacterial tyrosinases are a subgroup of oxidoreductases that oxidatively remove phenolic compounds, coupled to the reduction of molecular oxygen to water. The biochemical properties of bacterial tyrosinases have been investigated thoroughly in vitro within recent decades, while investigations focused on carbon fluxes in wetlands on a macroscopic level have remained a thriving yet separated research area so far. In the wake of climate change, however, anoxic conditions in wetland soils are threatened by reduced rainfall and prolonged summer drought. This potentially allows tyrosinase enzymes to reduce the concentration of phenolic compounds, which in turn will increase the release of stored carbon back into the atmosphere. To offer compelling evidence for the novel concept that bacterial tyrosinases are among the key enzymes influencing carbon cycling in wetland ecosystems first, bacterial organisms indigenous to wetland ecosystems that harbor a TYR gene within their respective genome (tyr+) have been identified, which revealed a phylogenetically diverse community of tyr+ bacteria indigenous to wetlands based on genomic sequencing data. Bacterial TYR host organisms covering seven phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes, Nitrospirae, Planctomycetes, and Proteobacteria) have been identified within various wetland ecosystems (peatlands, marshes, mangrove forests, bogs, and alkaline soda lakes) which cover a climatic continuum ranging from high arctic to tropic ecosystems. Second, it is demonstrated that (in vitro) bacterial TYR activity is commonly observed at pH values characteristic for wetland ecosystems (ranging from pH 3.5 in peatlands and freshwater swamps to pH 9.0 in soda lakes and freshwater marshes) and toward phenolic compounds naturally present within wetland environments (p-coumaric acid, gallic acid, protocatechuic acid, p-hydroxybenzoic acid, caffeic acid, catechin, and epicatechin). Third, analyzing the available data confirmed that bacterial host organisms tend to exhibit in vitro growth optima at pH values similar to their respective wetland habitats. Based on these findings, it is concluded that, following increased aeration of previously anoxic wetland soils due to climate change, TYRs are among the enzymes capable of reducing the concentration of phenolic compounds present within wetland ecosystems, which will potentially destabilize vast amounts of carbon stored in these ecosystems. Finally, promising approaches to mitigate the detrimental effects of increased TYR activity in wetland ecosystems and the requirement of future investigations of the abundance and activity of TYRs in an environmental setting are presented.
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4
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Kipouros I, Stańczak A, Ginsbach JW, Andrikopoulos PC, Rulíšek L, Solomon EI. Elucidation of the tyrosinase/O 2/monophenol ternary intermediate that dictates the monooxygenation mechanism in melanin biosynthesis. Proc Natl Acad Sci U S A 2022; 119:e2205619119. [PMID: 35939688 PMCID: PMC9389030 DOI: 10.1073/pnas.2205619119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 07/05/2022] [Indexed: 11/18/2022] Open
Abstract
Melanins are highly conjugated biopolymer pigments that provide photoprotection in a wide array of organisms, from bacteria to humans. The rate-limiting step in melanin biosynthesis, which is the ortho-hydroxylation of the amino acid L-tyrosine to L-DOPA, is catalyzed by the ubiquitous enzyme tyrosinase (Ty). Ty contains a coupled binuclear copper active site that binds O2 to form a μ:η2:η2-peroxide dicopper(II) intermediate (oxy-Ty), capable of performing the regioselective monooxygenation of para-substituted monophenols to catechols. The mechanism of this critical monooxygenation reaction remains poorly understood despite extensive efforts. In this study, we have employed a combination of spectroscopic, kinetic, and computational methods to trap and characterize the elusive catalytic ternary intermediate (Ty/O2/monophenol) under single-turnover conditions and obtain molecular-level mechanistic insights into its monooxygenation reactivity. Our experimental results, coupled with quantum-mechanics/molecular-mechanics calculations, reveal that the monophenol substrate docks in the active-site pocket of oxy-Ty fully protonated, without coordination to a copper or cleavage of the μ:η2:η2-peroxide O-O bond. Formation of this ternary intermediate involves the displacement of active-site water molecules by the substrate and replacement of their H bonds to the μ:η2:η2-peroxide by a single H bond from the substrate hydroxyl group. This H-bonding interaction in the ternary intermediate enables the unprecedented monooxygenation mechanism, where the μ-η2:η2-peroxide O-O bond is cleaved to accept the phenolic proton, followed by substrate phenolate coordination to a copper site concomitant with its aromatic ortho-hydroxylation by the nonprotonated μ-oxo. This study provides insights into O2 activation and reactivity by coupled binuclear copper active sites with fundamental implications in biocatalysis.
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Affiliation(s)
- Ioannis Kipouros
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Agnieszka Stańczak
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 166 10, Prague 6, Czech Republic
- Faculty of Science, Charles University, 128 00 Prague 2, Czech Republic
| | - Jake W. Ginsbach
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Prokopis C. Andrikopoulos
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 166 10, Prague 6, Czech Republic
| | - Lubomír Rulíšek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, 166 10, Prague 6, Czech Republic
| | - Edward I. Solomon
- Department of Chemistry, Stanford University, Stanford, CA 94305
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025
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Schneider R, Engesser TA, Näther C, Krossing I, Tuczek F. Copper‐Catalyzed Monooxygenation of Phenols: Evidence for a Mononuclear Reaction Mechanism. Angew Chem Int Ed Engl 2022; 61:e202202562. [PMID: 35344617 PMCID: PMC9323449 DOI: 10.1002/anie.202202562] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Indexed: 11/17/2022]
Abstract
The CuI salts [Cu(CH3CN)4]PF and [Cu(oDFB)2]PF with the very weakly coordinating anion Al(OC(CF3)3)4− (PF) as well as [Cu(NEt3)2]PF comprising the unique, linear bis‐triethylamine complex [Cu(NEt3)2]+ were synthesized and examined as catalysts for the conversion of monophenols to o‐quinones. The activities of these CuI salts towards monooxygenation of 2,4‐di‐tert‐butylphenol (DTBP‐H) were compared to those of [Cu(CH3CN)4]X salts with “classic” anions (BF4−, OTf−, PF6−), revealing an anion effect on the activity of the catalyst and a ligand effect on the reaction rate. The reaction is drastically accelerated by employing CuII‐semiquinone complexes as catalysts, indicating that formation of a CuII complex precedes the actual catalytic cycle. This result and other experimental observations show that with these systems the oxygenation of monophenols does not follow a dinuclear, but a mononuclear pathway analogous to that of topaquinone cofactor biosynthesis in amine oxidase.
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Affiliation(s)
- Rebecca Schneider
- Institut für Anorganische Chemie Christian-Albrechts-Universität zu Kiel Max-Eyth-Straße 2 24118 Kiel Germany
| | - Tobias A. Engesser
- Institut für Anorganische Chemie Christian-Albrechts-Universität zu Kiel Max-Eyth-Straße 2 24118 Kiel Germany
| | - Christian Näther
- Institut für Anorganische Chemie Christian-Albrechts-Universität zu Kiel Max-Eyth-Straße 2 24118 Kiel Germany
| | - Ingo Krossing
- Institut für Anorganische und Analytische Chemie Albert-Ludwigs-Universität Freiburg Albertstraße 21 79104 Freiburg Germany
| | - Felix Tuczek
- Institut für Anorganische Chemie Christian-Albrechts-Universität zu Kiel Max-Eyth-Straße 2 24118 Kiel Germany
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6
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Schneider R, Engesser TA, Näther C, Krossing I, Tuczek F. Copper‐Catalyzed Monooxygenation of Phenols: Evidence for a Mononuclear Reaction Mechanism. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202202562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Rebecca Schneider
- Christian-Albrechts-Universität zu Kiel: Christian-Albrechts-Universitat zu Kiel Institute for Inorganic Chemistry Max-Eyth-Straße 2 24118 Kiel GERMANY
| | - Tobias A. Engesser
- Christian-Albrechts-Universitat zu Kiel Institut für Anorganische Chemie Otto-Hahn-Platz 10 24118 Kiel GERMANY
| | - Christian Näther
- Christian-Albrechts-Universität zu Kiel: Christian-Albrechts-Universitat zu Kiel Institute for Inorganic Chemistry Max-Eyth-Straße 2 24118 Kiel GERMANY
| | - Ingo Krossing
- University of Freiburg: Albert-Ludwigs-Universitat Freiburg Institute for Inorganic and Analytical Chemistry Albertstr. 21 79104 Freiburg i. Br. GERMANY
| | - Felix Tuczek
- Christian-Albrechts-Universität zu Kiel: Christian-Albrechts-Universitat zu Kiel Institute for Inorganic Chemistry Max-Eyth-Straße 2 24118 Kiel GERMANY
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Panis F, Krachler RF, Krachler R, Rompel A. Expression, Purification, and Characterization of a Well-Adapted Tyrosinase from Peatlands Identified by Partial Community Analysis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:11445-11454. [PMID: 34156250 PMCID: PMC8375020 DOI: 10.1021/acs.est.1c02514] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 05/23/2021] [Accepted: 05/24/2021] [Indexed: 05/30/2023]
Abstract
In peatlands, bacterial tyrosinases (TYRs) are proposed to act as key regulators of carbon storage by removing phenolic compounds, which inhibit the degradation of organic carbon. Historically, TYR activity has been blocked by anoxia resulting from persistent waterlogging; however, recent events of prolonged summer drought have boosted TYR activity and, consequently, the release of carbon stored in the form of organic compounds from peatlands. Since 30% of the global soil carbon stock is stored in peatlands, a profound understanding of the production and activity of TYRs is essential to assess the impact of carbon dioxide emitted from peatlands on climate change. TYR partial sequences identified by degenerated primers suggest a versatile TYR enzyme community naturally present in peatlands, which is produced by a phylogenetically diverse spectrum of bacteria, including Proteobacteria and Actinobacteria. One full-length sequence of an extracellular TYR (SzTYR) identified from a soda-rich inland salt marsh has been heterologously expressed and purified. SzTYR exhibits a molecular mass of 30 891.8 Da and shows a pH optimum of 9.0. Spectroscopic studies and kinetic investigations characterized SzTYR as a tyrosinase and proved its activity toward monophenols (coumaric acid), diphenols (caffeic acid, protocatechuic acid), and triphenols (gallic acid) naturally present in peatlands.
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Affiliation(s)
- Felix Panis
- Universität
Wien, Fakultät
für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Wien, Austria
| | - Rudolf F. Krachler
- Fakultät
für Chemie, Institut für Anorganische Chemie, Universität Wien, Althanstraße 14, 1090 Wien, Austria
| | - Regina Krachler
- Fakultät
für Chemie, Institut für Anorganische Chemie, Universität Wien, Althanstraße 14, 1090 Wien, Austria
| | - Annette Rompel
- Universität
Wien, Fakultät
für Chemie, Institut für Biophysikalische Chemie, Althanstraße 14, 1090 Wien, Austria
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Matoba Y, Oda K, Muraki Y, Masuda T. The basicity of an active-site water molecule discriminates between tyrosinase and catechol oxidase activity. Int J Biol Macromol 2021; 183:1861-1870. [PMID: 34089758 DOI: 10.1016/j.ijbiomac.2021.05.206] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 05/27/2021] [Accepted: 05/30/2021] [Indexed: 11/26/2022]
Abstract
Tyrosinase (Ty) and catechol oxidase (CO) are members of type-3 copper enzymes. While Ty catalyzes both phenolase and catecholase reactions, CO catalyzes only the latter reaction. In the present study, Ty was found to catalyze the catecholase reaction, but hardly the phenolase reaction in the presence of the metallochaperon called "caddie protein (Cad)". The ability of the substrates to dissociate the motif shielding the active-site pocket seems to contribute critically to the substrate specificity of Ty. In addition, a mutation at the N191 residue, which forms a hydrogen bond with a water molecule near the active center, decreased the inherent ratio of phenolase versus catecholase activity. Unlike the wild-type complex, reaction intermediates were not observed when the catalytic reaction toward the Y98 residue of Cad was progressed in the crystalline state. The increased basicity of the water molecule may be necessary to inhibit the proton transfer from the conjugate acid to a hydroxide ion bridging the two copper ions. The deprotonation of the substrate hydroxyl by the bridging hydroxide seems to be significant for the efficient catalytic cycle of the phenolase reaction.
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Affiliation(s)
- Yasuyuki Matoba
- Faculty of Pharmacy, Yasuda Women's University, Yasuhigashi 6-13-1, Asaminami-ku, Hiroshima, 731-0153, Japan.
| | - Kosuke Oda
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551, Japan
| | - Yoshimi Muraki
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Kasumi 1-2-3, Minami-ku, Hiroshima 734-8551, Japan
| | - Taro Masuda
- Division of Applied Biological Science, Faculty of Agriculture, Setsunan University, 45-1 Nagaotoge-cho, Hirakata, Osaka 573-0101, Japan
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Tat-Dependent Heterologous Secretion of Recombinant Tyrosinase by Pseudomonas fluorescens Is Aided by a Translationally Fused Caddie Protein. Appl Environ Microbiol 2019; 85:AEM.01350-19. [PMID: 31399411 DOI: 10.1128/aem.01350-19] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 08/01/2019] [Indexed: 01/29/2023] Open
Abstract
Tyrosinase is a monooxygenase that catalyzes both the hydroxylation of p-hydroxyphenyl moieties to o-catechols and the oxidation of o-catechols to o-quinones. Apart from its critical functionality in melanogenesis and the synthesis of various neurotransmitters, this enzyme is also used in a variety of biotechnological applications, most notably mediating covalent cross-linking between polymers containing p-hydroxyphenyl groups, forming a hydrogel. Tyrosinases from the genus Streptomyces are usually secreted as a complex with their caddie protein. In this study, we report an increased secretion efficiency observed when the Streptomyces antibioticus tyrosinase gene melC2 was introduced into Pseudomonas fluorescens along with its caddie protein gene melC1, which has the DNA sequence for the Tat (twin-arginine translocation) signal.IMPORTANCE We observed that the S. antibioticus extracellular tyrosinase secretion level was even higher in its nonnatural translationally conjugated fusion protein form than in the natural complex of two separated polypeptides. The results of this study demonstrate that tyrosinase-expressing P. fluorescens can be a stable source of bacterial tyrosinase through exploiting the secretory machinery of P. fluorescens.
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Detection of tyramine and tyrosinase activity using red region emission NaGdF4:Yb,Er@NaYF4 upconversion nanoparticles. Talanta 2019; 197:558-566. [DOI: 10.1016/j.talanta.2019.01.079] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 01/13/2019] [Accepted: 01/18/2019] [Indexed: 01/05/2023]
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Matoba Y, Kihara S, Bando N, Yoshitsu H, Sakaguchi M, Kayama K, Yanagisawa S, Ogura T, Sugiyama M. Catalytic mechanism of the tyrosinase reaction toward the Tyr98 residue in the caddie protein. PLoS Biol 2018; 16:e3000077. [PMID: 30596633 PMCID: PMC6312201 DOI: 10.1371/journal.pbio.3000077] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Accepted: 12/03/2018] [Indexed: 11/21/2022] Open
Abstract
Tyrosinase (EC 1.14.18.1), a copper-containing monooxygenase, catalyzes the conversion of phenol to the corresponding ortho-quinone. The Streptomyces tyrosinase is generated as a complex with a “caddie” protein that facilitates the transport of two copper ions into the active center. In our previous study, the Tyr98 residue in the caddie protein, which is accommodated in the pocket of active center of tyrosinase, has been found to be converted to a reactive quinone through the formations of the μ-η2:η2-peroxo-dicopper(II) and Cu(II)-dopasemiquinone intermediates. Until now—despite extensive studies for the tyrosinase reaction based on the crystallographic analysis, low-molecular-weight models, and computer simulations—the catalytic mechanism has been unable to be made clear at an atomic level. To make the catalytic mechanism of tyrosinase clear, in the present study, the cryo-trapped crystal structures were determined at very high resolutions (1.16–1.70 Å). The structures suggest the existence of an important step for the tyrosinase reaction that has not yet been found: that is, the hydroxylation reaction is triggered by the movement of CuA, which induces the syn-to-anti rearrangement of the copper ligands after the formation of μ-η2:η2-peroxo-dicopper(II) core. By the rearrangement, the hydroxyl group of the substrate is placed in an equatorial position, allowing the electrophilic attack to the aromatic ring by the Cu2O2 oxidant. The cryo-trapped crystal structures of tyrosinase in a complex with its “caddie” protein reveal structural insight into the catalytic mechanism of tyrosinase, the rate-limiting enzyme in the production of melanin. Tyrosinase is an enzyme that controls a rate-limiting reaction of melanogenesis: it catalyzes the conversion of a phenol to the corresponding ortho-quinone. Streptomyces tyrosinase is formed as a complex, with a “caddie” protein that assists with the transport of the two copper ions into the enzyme’s active center. In our previous study, we showed that the Tyr98 residue in the caddie protein, which is accommodated in the pocket of active center of tyrosinase, is converted to a reactive quinone through the formations of the μ-η2:η2-peroxo-dicopper(II) and Cu(II)-dopasemiquinone intermediates. Until now—despite extensive studies of the tyrosinase reaction based on the crystallographic analysis, low-molecular-weight model systems, and computer simulations—the catalytic mechanism was unclear at an atomic level. To understand the catalytic mechanism of tyrosinase in detail, we determined the cryo-trapped crystal structures at very high resolutions, which suggest an important new step for the tyrosinase reaction: the hydroxylation reaction triggered by the movement of CuA, which induces the syn-to-anti rearrangement of the copper ligands after the formation of μ-η2:η2-peroxo-dicopper(II) core.
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Affiliation(s)
- Yasuyuki Matoba
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan
- * E-mail: (YM); (MS)
| | - Shogo Kihara
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Naohiko Bando
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Hironari Yoshitsu
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan
| | - Miyuki Sakaguchi
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Hyogo, Japan
| | - Kure’e Kayama
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Hyogo, Japan
| | - Sachiko Yanagisawa
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Hyogo, Japan
| | - Takashi Ogura
- Picobiology Institute, Graduate School of Life Science, University of Hyogo, Hyogo, Japan
| | - Masanori Sugiyama
- Graduate School of Biomedical & Health Sciences, Hiroshima University, Hiroshima, Japan
- * E-mail: (YM); (MS)
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