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Pupart H, Lukk T, Väljamäe P. Dye-decolorizing peroxidase of Thermobifida halotolerance displays complex kinetics with both substrate inhibition and apparent positive cooperativity. Arch Biochem Biophys 2024; 754:109931. [PMID: 38382807 DOI: 10.1016/j.abb.2024.109931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Revised: 02/15/2024] [Accepted: 02/16/2024] [Indexed: 02/23/2024]
Abstract
Dye-decolorizing peroxidases (DyPs) have been intensively investigated for the purpose of industrial dye decolourization and lignin degradation. Unfortunately, the characterization of these peroxidases is hampered by their non-Michaelis-Menten kinetics, exemplified by substrate inhibition and/or positive cooperativity. Although often observed, the underlying mechanisms behind the unusual kinetics of DyPs are poorly understood. Here we studied the kinetics of the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydroquinones, and anthraquinone dyes by DyP from the bacterium Thermobifida halotolerans (ThDyP) and solved its crystal structure. We also provide rate equations for different kinetic mechanisms explaining the complex kinetics of heme peroxidases. Kinetic studies along with the analysis of the structure of ThDyP suggest that the substrate inhibition is caused by the non-productive binding of ABTS to the enzyme resting state. Strong irreversible inactivation of ThDyP by H2O2 in the absence of ABTS suggests that the substrate inhibition by H2O2 may be caused by the non-productive binding of H2O2 to compound I. Positive cooperativity was observed only with the oxidation of ABTS but not with the two electron-donating substrates. Although the conventional mechanism of cooperativity cannot be excluded, we propose that the oxidation of ABTS assumes the simultaneous binding of two ABTS molecules to reduce compound I to the enzyme resting state, and this causes the apparent positive cooperativity.
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Affiliation(s)
- Hegne Pupart
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618, Tallinn, Estonia.
| | - Tiit Lukk
- Department of Chemistry and Biotechnology, Tallinn University of Technology, Akadeemia tee 15, 12618, Tallinn, Estonia.
| | - Priit Väljamäe
- Institute of Molecular and Cell Biology, University of Tartu, Riia 23b-202, 51010, Tartu, Estonia.
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Pupart H, Vastšjonok D, Lukk T, Väljamäe P. Dye-Decolorizing Peroxidase of Streptomyces coelicolor ( ScDyPB) Exists as a Dynamic Mixture of Kinetically Different Oligomers. ACS Omega 2024; 9:3866-3876. [PMID: 38284010 PMCID: PMC10809370 DOI: 10.1021/acsomega.3c07963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 12/19/2023] [Accepted: 12/21/2023] [Indexed: 01/30/2024]
Abstract
Dye-decolorizing peroxidases (DyPs) are heme-dependent enzymes that catalyze the oxidation of various substrates including environmental pollutants such as azo dyes and also lignin. DyPs often display complex non-Michaelis-Menten kinetics with substrate inhibition or positive cooperativity. Here, we performed in-depth kinetic characterization of the DyP of the bacterium Streptomyces coelicolor (ScDyPB). The activity of ScDyPB was found to be dependent on its concentration in the working stock used to initiate the reactions as well as on the pH of the working stock. Furthermore, the above-listed conditions had different effects on the oxidation of 2,2'-azino-di(3-ethyl-benzothiazoline-6-sulfonic acid) (ABTS) and methylhydroquinone, suggesting that different mechanisms are used in the oxidation of these substrates. The kinetics of the oxidation of ABTS were best described by the model whereby ScDyPB exists as a mixture of two kinetically different enzyme forms. Both forms obey the ping-pong kinetic mechanism, but one form is substrate-inhibited by the ABTS, whereas the other is not. Gel filtration chromatography and dynamic light scattering analyses revealed that ScDyPB exists as a complex mixture of molecules with different sizes. We propose that ScDyPB populations with low and high degrees of oligomerization have different kinetic properties. Such enzyme oligomerization-dependent modulation of the kinetic properties adds further dimension to the complexity of the kinetics of DyPs but also suggests novel possibilities for the regulation of their catalytic activity.
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Affiliation(s)
- Hegne Pupart
- Department
of Chemistry and Biotechnology, Tallinn
University of Technology, 15 Akadeemia tee, Tallinn 12618, Estonia
| | - Darja Vastšjonok
- Institute
of Molecular and Cell Biology, University
of Tartu, Riia 23b-202, Tartu 51010, Estonia
| | - Tiit Lukk
- Department
of Chemistry and Biotechnology, Tallinn
University of Technology, 15 Akadeemia tee, Tallinn 12618, Estonia
| | - Priit Väljamäe
- Institute
of Molecular and Cell Biology, University
of Tartu, Riia 23b-202, Tartu 51010, Estonia
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Zovo K, Pupart H, Van Wieren A, Gillilan RE, Huang Q, Majumdar S, Lukk T. Substitution of the Methionine Axial Ligand of the T1 Copper for the Fungal-like Phenylalanine Ligand (M298F) Causes Local Structural Perturbations that Lead to Thermal Instability and Reduced Catalytic Efficiency of the Small Laccase from Streptomyces coelicolor A3(2). ACS Omega 2022; 7:6184-6194. [PMID: 35224382 PMCID: PMC8867573 DOI: 10.1021/acsomega.1c06668] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Accepted: 01/28/2022] [Indexed: 06/14/2023]
Abstract
Many industrial processes operate at elevated temperatures or within broad pH and salinity ranges. However, the utilization of enzymes to carry out biocatalysis in such processes is often impractical or even impossible. Laccases (EC 1.10.3.2), which constitute a large family of multicopper oxidases, have long been used in the industrial setting. Although fungal laccases are in many respects considered superior to their bacterial counterparts, the bacterial laccases have been receiving greater attention recently. Albeit lower in redox potential than fungal laccases, bacterial laccases are commonly thermally more stable, act within broader pH ranges, do not contain posttranslational modifications, and could therefore serve as a high potential scaffold for directed evolution for the production of enzymes with enhanced properties. Several examples focusing on the axial ligand mutations of the T1 copper site have been published in the past. However, structural evidence on the local and global changes induced by those mutations have thus far been of computational nature only. In this study, we set out to structurally and kinetically characterize a few of the most commonly reported axial ligand mutations of a bacterial small laccase (SLAC) from Streptomyces coelicolor. While one of the mutations (Met to Leu) equips the enzyme with better thermal stability, the other (Met to Phe) induces an opposite effect. These mutations cause local structural rearrangement of the T1 site as demonstrated by X-ray crystallography. Our analysis confirms past findings that for SLACs, single point mutations that change the identity of the axial ligand of the T1 copper are not enough to provide a substantial increase in the catalytic efficiency but can in some cases have a detrimental effect on the enzyme's thermal stability parameters instead.
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Affiliation(s)
- Kairit Zovo
- Department
of Chemistry and Biotechnology, Tallinn
University of Technology, Akadeemia tee 15, Tallinn 12618, Estonia
| | - Hegne Pupart
- Department
of Chemistry and Biotechnology, Tallinn
University of Technology, Akadeemia tee 15, Tallinn 12618, Estonia
| | - Arie Van Wieren
- Department
of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, Pennsylvania 15705, United States
| | - Richard E. Gillilan
- MacCHESS
(Macromolecular Diffraction Facility at CHESS), Cornell University, 161 Synchrotron Drive, Ithaca, New York 14850, United
States
| | - Qingqiu Huang
- MacCHESS
(Macromolecular Diffraction Facility at CHESS), Cornell University, 161 Synchrotron Drive, Ithaca, New York 14850, United
States
| | - Sudipta Majumdar
- Department
of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, Pennsylvania 15705, United States
| | - Tiit Lukk
- Department
of Chemistry and Biotechnology, Tallinn
University of Technology, Akadeemia tee 15, Tallinn 12618, Estonia
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