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Huang M, Cui P, Zhou J, Liu C, Wang Y. Theoretical study on the inhibition mechanisms of heavy metal ions on urease activity. CHEMOSPHERE 2023; 345:140416. [PMID: 37827462 DOI: 10.1016/j.chemosphere.2023.140416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 10/08/2023] [Accepted: 10/09/2023] [Indexed: 10/14/2023]
Abstract
Soil urease is highly sensitive to soil heavy metal pollution, and thus its activity can be used as bio-indicator of soil health. However, little is known about the inhibition mechanisms of heavy metals on urease. The effects of dimetallic substitution (i.e., Cd, Co, Cu, Hg, and Zn) on the binding of urea in the urease and its subsequent decomposition were studied using quantum chemical methodologies with a urease mimic (phthalazine-dinickel complex). The dimetallic substitution altered the structural features of the dimetal complexes and the M-O bond length between the dimetals and the carbonyl-O of coordinated urea molecules, weakening the binding energies of urea in dimetal complexes, which further affected the transformation of urea. In the urea decomposition via intra-molecular proton transfer, all dimetal complexes have a high activation barrier due to the weak binding of urea in complexes and hydrogen bonding within urea molecules, which are therefore difficult to occur spontaneously. In the urea decomposition via water-assisted inter-molecular proton transfer, the addition of water molecules decreased the energy barrier of urea decomposition. Regardless of the urea decomposition pathway, the dimetallic substitution altered the M-O bond length and hydrogen bond pattern of intermediates and transition states, and also affected the leave of the resulting NH3 from the dimetal complexes by regulating the C-N bond length within the decomposed urea molecule. Overall, the theoretical study provided insight into the molecular mechanisms of the inhibitory effects of heavy metals on urease activity.
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Affiliation(s)
- Meiying Huang
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Peixin Cui
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Jing Zhou
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China
| | - Cun Liu
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China.
| | - Yujun Wang
- State Key Laboratory of Soil & Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing, 210008, China; University of Chinese Academy of Sciences, Beijing, 100049, China
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Meelua W, Wanjai T, Thinkumrob N, Oláh J, Cairns JRK, Hannongbua S, Ryde U, Jitonnom J. A computational study of the reaction mechanism and stereospecificity of dihydropyrimidinase. Phys Chem Chem Phys 2023; 25:8767-8778. [PMID: 36912034 DOI: 10.1039/d2cp05262h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2023]
Abstract
Dihydropyrimidinase (DHPase) is a key enzyme in the pyrimidine pathway, the catabolic route for synthesis of β-amino acids. It catalyses the reversible conversion of 5,6-dihydrouracil (DHU) or 5,6-dihydrothymine (DHT) to the corresponding N-carbamoyl-β-amino acids. This enzyme has the potential to be used as a tool in the production of β-amino acids. Here, the reaction mechanism and origin of stereospecificity of DHPases from Saccharomyces kluyveri and Sinorhizobium meliloti CECT4114 were investigated and compared using a quantum mechanical cluster approach based on density functional theory. Two models of the enzyme active site were designed from the X-ray crystal structure of the native enzyme: a small cluster to characterize the mechanism and the stationary points and a large model to probe the stereospecificity and the role of stereo-gate-loop (SGL) residues. It is shown that a hydroxide ion first performs a nucleophilic attack on the substrate, followed by the abstraction of a proton by Asp358, which occurs concertedly with protonation of the ring nitrogen by the same residue. For the DHT substrate, the enzyme displays a preference for the L-configuration, in good agreement with experimental observation. Comparison of the reaction energetics of the two models reveals the importance of SGL residues in the stereospecificity of catalysis. The role of the conserved Tyr172 residue in transition-state stabilization is confirmed as the Tyr172Phe mutation increases the activation barrier of the reaction by ∼8 kcal mol-1. A detailed understanding of the catalytic mechanism of the enzyme could offer insight for engineering in order to enhance its activity and substrate scope.
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Affiliation(s)
- Wijitra Meelua
- Demonstration School, University of Phayao, Phayao 56000, Thailand
- Unit of Excellence in Computational Molecular Science and Catalysis, and Division of Chemistry, School of Science, University of Phayao, Phayao 56000, Thailand.
| | - Tanchanok Wanjai
- Unit of Excellence in Computational Molecular Science and Catalysis, and Division of Chemistry, School of Science, University of Phayao, Phayao 56000, Thailand.
| | - Natechanok Thinkumrob
- Unit of Excellence in Computational Molecular Science and Catalysis, and Division of Chemistry, School of Science, University of Phayao, Phayao 56000, Thailand.
| | - Julianna Oláh
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economics, Műegyetem rakpart 3, Budapest H-1111, Hungary
| | - James R Ketudat Cairns
- Center for Biomolecular Structure, Function and Application and School of Chemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
| | - Supa Hannongbua
- Department of Chemistry, Faculty of Science, Kasetsart University, Bangkok 10900, Thailand
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, Lund SE-221 00, Sweden
| | - Jitrayut Jitonnom
- Unit of Excellence in Computational Molecular Science and Catalysis, and Division of Chemistry, School of Science, University of Phayao, Phayao 56000, Thailand.
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Short-Term Supplementation of Sodium Nitrate vs. Sodium Chloride Increases Homoarginine Synthesis in Young Men Independent of Exercise. Int J Mol Sci 2022; 23:ijms231810649. [PMID: 36142560 PMCID: PMC9504822 DOI: 10.3390/ijms231810649] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2022] [Revised: 09/06/2022] [Accepted: 09/08/2022] [Indexed: 02/07/2023] Open
Abstract
The aim of the study was to investigate the effects of short-term oral administration of inorganic nitrate (NaNO3; n = 8) or placebo (NaCl; n = 9) (each 0.1 mmol/kg body weight/d for 9 days) on plasma amino acids, creatinine, and oxidative stress in healthy young men. At baseline, the plasma concentrations of amino acids did not differ between the groups. At the end of the study, the plasma concentrations of homoarginine (hArg; by 24%, p = 0.0001), citrulline and ornithine (Cit/Orn; by 16%, p = 0.015), and glutamine/glutamate (Gln/Glu; by 6%, p = 0.0003) were higher in the NaNO3 group compared to the NaCl group. The plasma concentrations of sarcosine (Sarc; by 28%, p < 0.0001), tyrosine (by 14%, p = 0.0051), phenylalanine (by 8%, p = 0.0026), and tryptophan (by 8%, p = 0.0047) were lower in the NaNO3 group compared to the NaCl group. These results suggest that nitrate administration affects amino-acid metabolism. The arginine/glycine amidinotransferase (AGAT) catalyzes two reactions: (1) the formation of l-homoarginine (hArg) and l-ornithine (Orn) from l-arginine (Arg) and l-lysine (Lys): Arg + Lys <−> hArg + Orn, with equilibrium constant Kharg; (2) the formation of guanidinoacetate (GAA) and Orn from Arg and glycine (Gly): Arg + Gly <−> GAA + Orn, with equilibrium constant Kgaa. The plasma Kgaa/KhArg ratio was lower in the NaNO3 group compared to the NaCl group (1.57 vs. 2.02, p = 0.0034). Our study suggests that supplementation of inorganic nitrate increases the AGAT-catalyzed synthesis of hArg and decreases the N-methyltransferase-catalyzed synthesis of GAA, the precursor of creatine. To our knowledge, this is the first study to demonstrate elevation of hArg synthesis by inorganic nitrate supplementation. Remarkably, an increase of 24% corresponds to the synthesis capacity of one kidney in healthy humans. Differences in the association between plasma concentrations of amino acids in the NaNO3 and NaCl groups suggest changes in amino-acid homeostasis. Plasma concentrations of the oxidative stress marker malondialdehyde (MDA) did not change after supplementation of NaNO3 or NaCl over the whole exercise time range. Plasma nitrite concentration turned out to be a more discriminant marker of NaNO3 ingestion than plasma nitrate (area under the receiver operating characteristic curve: 0.951 vs. 0.866, p < 0.0001 each).
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