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Martin CP, Chen M, Martinez MF, Ding Y, Caranto JD. The Ferric-Superoxo Intermediate of the TxtE Nitration Pathway Resists Reduction, Facilitating Its Reaction with Nitric Oxide. Biochemistry 2021; 60:2436-2446. [PMID: 34319079 DOI: 10.1021/acs.biochem.1c00416] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
TxtE is a cytochrome P450 (CYP) homologue that mediates the nitric oxide (NO)-dependent direct nitration of l-tryptophan (Trp) to form 4-nitro-l-tryptophan (4-NO2-Trp). A recent report showed evidence that TxtE activity requires NO to react with a ferric-superoxo intermediate. Given this minimal mechanism, it is not clear how TxtE avoids Trp hydroxylation, a mechanism that also traverses the ferric-superoxo intermediate. To provide insight into canonical CYP intermediates that TxtE can access, electron coupling efficiencies to form 4-NO2-Trp under single- or limited-turnover conditions were measured and compared to steady-state efficiencies. As previously reported, Trp nitration by TxtE is supported by the engineered self-sufficient variant, TB14, as well as by reduced putidaredoxin. Ferrous (FeII) TxtE exhibits excellent electron coupling (70%), which is 50-fold higher than that observed under turnover conditions. In addition, two- or four-electron reduced TB14 exhibits electron coupling (∼6%) that is 2-fold higher than that of one-electron reduced TB14 (3%). The combined results suggest (1) autoxidation is the sole TxtE uncoupling pathway and (2) the TxtE ferric-superoxo intermediate cannot be reduced by these electron transfer partners. The latter conclusion is further supported by ultraviolet-visible absorption spectral time courses showing neither spectral nor kinetic evidence for reduction of the ferric-superoxo intermediate. We conclude that resistance of the ferric-superoxo intermediate to reduction is a key feature of TxtE that increases the lifetime of the intermediate and enables its reaction with NO and efficient nitration activity.
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Affiliation(s)
- Christopher P Martin
- Department of Chemistry, University of Central Florida, 4111 Libra Drive, Room 255, Orlando, Florida 32816, United States
| | - Manyun Chen
- Department of Medicinal Chemistry, Center for Natural Products, Drug Discovery and Development, University of Florida, 1345 Center Drive, Room P6-27, Gainesville, Florida 32610, United States
| | - Maria F Martinez
- Department of Chemistry, University of Central Florida, 4111 Libra Drive, Room 255, Orlando, Florida 32816, United States
| | - Yousong Ding
- Department of Medicinal Chemistry, Center for Natural Products, Drug Discovery and Development, University of Florida, 1345 Center Drive, Room P6-27, Gainesville, Florida 32610, United States
| | - Jonathan D Caranto
- Department of Chemistry, University of Central Florida, 4111 Libra Drive, Room 255, Orlando, Florida 32816, United States
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Nöth M, Hussmann L, Belthle T, El-Awaad I, Davari MD, Jakob F, Pich A, Schwaneberg U. MicroGelzymes: pH-Independent Immobilization of Cytochrome P450 BM3 in Microgels. Biomacromolecules 2020; 21:5128-5138. [PMID: 33206503 DOI: 10.1021/acs.biomac.0c01262] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Microgels are an emerging class of "ideal" enzyme carriers because of their chemical and process stability, biocompatibility, and high enzyme loading capability. In this work, we synthesized a new type of permanently positively charged poly(N-vinylcaprolactam) (PVCL) microgel with 1-vinyl-3-methylimidazolium (quaternization of nitrogen by methylation of N-vinylimidazole moieties) as a comonomer (PVCL/VimQ) through precipitation polymerization. The PVCL/VimQ microgels were characterized with respect to their size, charge, swelling degree, and temperature responsiveness in aqueous solutions. P450 monooxygenases are usually challenging to immobilize, and often, high activity losses occur after the immobilization (in the case of P450 BM3 from Bacillus megaterium up to 100% loss of activity). The electrostatic immobilization of P450 BM3 in permanently positively charged PVCL/VimQ microgels was achieved without the loss of catalytic activity at the pH optimum of P450 BM3 (pH 8; ∼9.4 nmol 7-hydroxy-3-carboxy coumarin ethyl ester/min for free and immobilized P450 BM3); the resulting P450-microgel systems were termed P450 MicroGelzymes (P450 μ-Gelzymes). In addition, P450 μ-Gelzymes offer the possibility of reversible ionic strength-triggered release and re-entrapment of the biocatalyst in processes (e.g., for catalyst reuse). Finally, a characterization of the potential of P450 μ-Gelzymes to provide resistance against cosolvents (acetonitrile, dimethyl sulfoxide, and 2-propanol) was performed to evaluate the biocatalytic application potential.
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Affiliation(s)
- Maximilian Nöth
- Institute of Biotechnology, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany.,DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany
| | - Larissa Hussmann
- DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany.,Functional and Interactive Polymers, Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany
| | - Thomke Belthle
- DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany.,Functional and Interactive Polymers, Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany
| | - Islam El-Awaad
- Institute of Biotechnology, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany.,DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany.,Department of Pharmacognosy, Faculty of Pharmacy, Assiut University, 71526 Assiut, Egypt
| | - Mehdi D Davari
- Institute of Biotechnology, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany
| | - Felix Jakob
- Institute of Biotechnology, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany.,DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany
| | - Andrij Pich
- DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany.,Functional and Interactive Polymers, Institute of Technical and Macromolecular Chemistry, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany.,Aachen Maastricht Institute for Biobased Materials (AMIBM), Maastricht University, Brightlands Chemelot Campus, Urmonderbaan 22, 6167 RD Geleen, The Netherlands
| | - Ulrich Schwaneberg
- Institute of Biotechnology, RWTH Aachen University, Worringerweg 3, 52074 Aachen, Germany.,DWI-Leibniz-Institute for Interactive Materials e.V., Forckenbeckstraβe 50, 52074 Aachen, Germany
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Abstract
Many artificial enzymes that catalyze redox reactions have important energy, environmental, and medical applications. Native metalloenzymes use a set of redox-active amino acids and cofactors as redox centers, with a potential range between -700 and +800 mV versus standard hydrogen electrode (SHE, all reduction potentials are versus SHE). The redox potentials and the orientation of redox centers in native metalloproteins are optimal for their redox chemistry. However, the limited number and potential range of native redox centers challenge the design and optimization of novel redox chemistry in metalloenzymes. Artificial metalloenzymes use non-native redox centers and could go far beyond the natural range of redox potentials for novel redox chemistry. In addition to designing protein monomers, strategies for increasing the electron transfer rate in self-assembled protein complexes and protein-electrode or -nanomaterial interfaces will be discussed. Redox reactions in proteins occur on redox active amino acid residues (Tyr, Trp, Met, Cys, etc.) and cofactors (iron sulfur clusters, flavin, heme, etc.). The redox potential of these redox centers cover a ∼1.5 V range and is optimized for their specific functions. Despite recent progress, tuning the redox potential for amino acid residues or cofactors remains challenging. Many redox-active unnatural amino acids (UAAs) can be incorporated into protein via genetic codon expansion. Their redox potentials extend the range of physiologically relevant potentials. Indeed, installing new redox cofactors with fined-tuned redox potentials is essential for designing novel redox enzymes. By combining UAA and redox cofactor incorporation, we harnessed light energy to reduce CO2 in a fluorescent protein, mimicking photosynthetic apparatus in nature. Manipulating the position and reduction potential of redox centers inside proteins is important for optimizing the electron transfer rate and the activity of artificial enzymes. Learning from the native electron transfer complex, protein-protein interactions can be enhanced by increasing the electrostatic interaction between proteins. An artificial oxidase showed close to native enzyme activity with optimized interaction with electron transfer partner and increased electron transfer efficiency. In addition to the de novo design of protein-protein interaction, protein self-assembly methods using scaffolds, such as proliferating cell nuclear antigen, to efficiently anchor enzymes and their redox partners. The self-assembly process enhances electron transfer efficiency and enzyme activity by bringing redox centers into close proximity of each other. In addition to protein self-assembly, protein-electrode or protein-nanomaterial self-assembly can also promote efficient electron transfer from inorganic materials to enzyme active sites. Such hybrid systems combine the efficiency of enzyme reactions and the robustness of electrodes or nanomaterials, often with advantageous catalytic activities. By combining these strategies, we can not only mimic some of nature's most fascinating reactions, such as photosynthesis and aerobic respiration, but also transcend nature toward environmental, energy, and health applications.
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Affiliation(s)
- Yang Yu
- Department of Biochemical Engineering and Institute for Synthetic Biosystem, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, 5 Zhongguancun South Street, Haidian
District, Beijing 100081, China
| | - Xiaohong Liu
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China
| | - Jiangyun Wang
- Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing 100101, China
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Velasco-Lozano S, López-Gallego F. Wiring step-wise reactions with immobilized multi-enzyme systems. BIOCATAL BIOTRANSFOR 2017. [DOI: 10.1080/10242422.2017.1310208] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | - Fernando López-Gallego
- Heterogeneous Biocatalysis Group, CIC biomaGUNE, Donostia, Spain
- Basque Foundation for Science, IKERBASQUE, Bilbao, Spain
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