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Rossi M, Tomaselli F, Hochkoeppler A. The four subunits of rabbit skeletal muscle lactate dehydrogenase do not exert their catalytic action additively. Biochem Biophys Res Commun 2024; 690:149294. [PMID: 38011772 DOI: 10.1016/j.bbrc.2023.149294] [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: 11/12/2023] [Accepted: 11/17/2023] [Indexed: 11/29/2023]
Abstract
Oligomeric enzymes containing multiple active sites are usually considered to perform their catalytic action at higher rates when compared with their monomeric counterparts. This implies, in turn, that the activity performed by different holoenzyme subunits features additivity. Nevertheless, the extent of this additivity occurring in holoenzymes is far from being adequately understood. To tackle this point, we used tetrameric rabbit lactate dehydrogenase (rbLDH) as a model system to assay the reduction of pyruvate catalysed by this enzyme at the expense of β-NADH under pre-steady-state conditions. In particular, we observed the kinetics of reactions triggered by concentrations of β-NADH equimolar to 1, 2, 3, or all 4 subunits of the rbLDH holoenzyme, in the presence of an excess of pyruvate. Surprisingly, when the concentration of the limiting reactant exceeded that of a single holoenzyme subunit, we observed a sharp slowdown of the enzyme conformational rearrangements associated to the generation and the release of l-lactate. Furthermore, using a model to interpret the complex kinetics observed under the highest concentration of the limiting reactant, we estimated the diversity of the rates describing the action of the different rbLDH subunits.
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Affiliation(s)
- Martina Rossi
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Fabio Tomaselli
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy; CSGI, University of Firenze, Via della Lastruccia 3, 50019, Sesto Fiorentino, FI, Italy.
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Kovermann M, Stefan A, Palazzetti C, Immler F, Dal Piaz F, Bernardi L, Cimone V, Bellone ML, Hochkoeppler A. The Mycobacterium tuberculosis protein tyrosine phosphatase MptpA features a pH dependent activity overlapping the bacterium sensitivity to acidic conditions. Biochimie 2023; 213:66-81. [PMID: 37201648 DOI: 10.1016/j.biochi.2023.04.014] [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: 02/09/2023] [Revised: 04/03/2023] [Accepted: 04/24/2023] [Indexed: 05/20/2023]
Abstract
The Mycobacterium tuberculosis low-molecular weight protein tyrosine phosphatase (MptpA) is responsible for the inhibition of phagosome-lysosome fusion and is essential for the bacterium pathogenicity. This inhibition implies that M. tuberculosis is not exposed to a strongly acidic environment in vivo, enabling successful propagation in host cells. Remarkably, MptpA has been previously structurally and functionally investigated, with special emphasis devoted to the enzyme properties at pH 8.0. Considering that the virulence of M. tuberculosis is strictly dependent on the avoidance of acidic conditions in vivo, we analysed the pH-dependence of the structural and catalytic properties of MptpA. Here we show that this enzyme undergoes pronounced conformational rearrangements when exposed to acidic pH conditions, inducing a severe decrease of the enzymatic catalytic efficiency at the expense of phosphotyrosine (pTyr). In particular, a mild decrease of pH from 6.5 to 6.0 triggers a significant increase of K0.5 of MptpA for phosphotyrosine, the phosphate group of which we determined to feature a pKa2 equal to 5.7. Surface plasmon resonance experiments confirmed that MptpA binds poorly to pTyr at pH values < 6.5. Notably, the effectiveness of the MptpA competitive inhibitor L335-M34 at pH 6 does largely outperform the inhibition exerted at neutral or alkaline pH values. Overall, our observations indicate a pronounced sensitivity of MptpA to acidic pH conditions, and suggest the search for competitive inhibitors bearing a negatively charged group featuring pKa values lower than that of the substrate phosphate group.
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Affiliation(s)
- Michael Kovermann
- Department of Chemistry, University of Konstanz, Universitätstraße 10, 78464, Konstanz, Germany
| | - Alessandra Stefan
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy; CSGI, University of Florence, Via della Lastruccia 3, 50019, Sesto Fiorentino, Firenze, Italy
| | - Chiara Palazzetti
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Fabian Immler
- Department of Chemistry, University of Konstanz, Universitätstraße 10, 78464, Konstanz, Germany
| | - Fabrizio Dal Piaz
- Department of Medicine, University of Salerno, Via Giovanni Paolo II 132, 84084, Fisciano, Italy
| | - Luca Bernardi
- Department of Industrial Chemistry "Toson Montanaro", University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Valentina Cimone
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy
| | - Maria Laura Bellone
- Department of Pharmacy, University of Salerno, Via Giovanni Paolo II 132, 84084, Fisciano, Italy
| | - Alejandro Hochkoeppler
- Department of Pharmacy and Biotechnology, University of Bologna, Viale Risorgimento 4, 40136, Bologna, Italy; CSGI, University of Florence, Via della Lastruccia 3, 50019, Sesto Fiorentino, Firenze, Italy.
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Sulyman AO, Fulcher J, Crossley S, Fatokun AA, Olorunniji FJ. Shikonin and Juglone Inhibit Mycobacterium tuberculosis Low-Molecular-Weight Protein Tyrosine Phosphatase a (Mt-PTPa). BIOTECH 2023; 12:59. [PMID: 37754203 PMCID: PMC10526854 DOI: 10.3390/biotech12030059] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 08/21/2023] [Accepted: 09/12/2023] [Indexed: 09/28/2023] Open
Abstract
Low-molecular-weight protein tyrosine phosphatases (LMW-PTPs) are involved in promoting the intracellular survival of Mycobacterium tuberculosis (Mtb), the causative organism of tuberculosis. These PTPs directly alter host signalling pathways to evade the hostile environment of macrophages and avoid host clearance. Among these, protein tyrosine phosphatase A (Mt-PTPa) is implicated in phagosome acidification failure, thereby inhibiting phagosome maturation to promote Mycobacterium tuberculosis (Mtb) survival. In this study, we explored Mt-PTPa as a potential drug target for treating Mtb. We started by screening a library of 502 pure natural compounds against the activities of Mt-PTPa in vitro, with a threshold of 50% inhibition of activity via a <500 µM concentration of the candidate drugs. The initial screen identified epigallocatechin, myricetin, rosmarinic acid, and shikonin as hits. Among these, the naphthoquinone, shikonin (5, 8-dihydroxy-2-[(1R)-1-hydroxy-4-methyl-3-pentenyl]-1,4-naphthoquinone), showed the strongest inhibition (IC50 33 µM). Further tests showed that juglone (5-hydroxy-1,4-naphthalenedione), another naphthoquinone, displayed similar potent inhibition of Mt-PTPa to shikonin. Kinetic analysis of the inhibition patterns suggests a non-competitive inhibition mechanism for both compounds, with inhibitor constants (Ki) of 8.5 µM and 12.5 µM for shikonin and juglone, respectively. Our findings are consistent with earlier studies suggesting that Mt-PTPa is susceptible to specific allosteric modulation via a non-competitive or mixed inhibition mechanism.
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Affiliation(s)
- Abdulhakeem O. Sulyman
- Department of Biochemistry, Faculty of Pure and Applied Sciences, Kwara State University, Malete 241103, Nigeria
- School of Pharmacy & Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK
| | - Jessie Fulcher
- School of Pharmacy & Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK
| | - Samuel Crossley
- School of Pharmacy & Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK
| | - Amos A. Fatokun
- School of Pharmacy & Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK
| | - Femi J. Olorunniji
- School of Pharmacy & Biomolecular Sciences, Faculty of Science, Liverpool John Moores University, Byrom Street, Liverpool L3 3AF, UK
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Menegatti ACO. Targeting protein tyrosine phosphatases for the development of antivirulence agents: Yersinia spp. and Mycobacterium tuberculosis as prototypes. BIOCHIMICA ET BIOPHYSICA ACTA. PROTEINS AND PROTEOMICS 2022; 1870:140782. [PMID: 35470106 DOI: 10.1016/j.bbapap.2022.140782] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 04/15/2022] [Accepted: 04/19/2022] [Indexed: 06/14/2023]
Abstract
Protein phosphorylation mediated by protein kinases and phosphatases has a central regulatory function in many cellular processes in eukaryotes and prokaryotes. As a result, several diseases caused by imbalance in phosphorylation levels are known, especially due to protein tyrosine phosphatases (PTPs) activity, an important family of signaling enzymes. Furthermore, over the last decades several studies have shown the main role of PTPs in pathogenic bacteria: they are associated with growth, cell division, cell wall biosynthesis, biofilm formation, metabolic processes, as well as virulence factor. In this way, PTPs have ascended as targets for antibacterial drug design, particularly in view of the antibiotic resistance in pathogenic bacteria, which demands novel therapeutics strategies. Targeting secreted PTPs is an antivirulence strategy to combat the emergence of antimicrobial resistance (AMR). This review focuses on the recent advances in understanding the role of PTPs and the approaches to target them, with an emphasis in Yersinia spp. and Mycobacterium tuberculosis pathogenesis.
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Affiliation(s)
- Angela Camila Orbem Menegatti
- Departamento de Biologia Molecular, Centro de Ciências Exatas e da Natureza, Universidade Federal da Paraíba, Paraíba, Brazil.
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