1
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Guan ZB, Deng XT, Zhang ZH, Xu GC, Cheng WL, Liao XR, Cai YJ. Engineering Glucosamine-6-Phosphate Synthase to Achieve Efficient One-Step Biosynthesis of Glucosamine. ACS Chem Biol 2024; 19:1237-1242. [PMID: 38723147 DOI: 10.1021/acschembio.4c00144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/22/2024]
Abstract
As an important functional monosaccharide, glucosamine (GlcN) is widely used in fields such as medicine, food nutrition, and health care. Here, we report a distinct GlcN biosynthesis method that utilizes engineered Bacillus subtilis glucosamine-6-phosphate synthase (BsGlmS) to convert D-fructose to directly generate GlcN. The best variant obtained by using a combinatorial active-site saturation test/iterative saturation mutagenesis (CAST/ISM) strategy was a quadruple mutant S596D/V597G/S347H/G299Q (BsGlmS-BK19), which has a catalytic activity 1736-fold that of the wild type toward D-fructose. Upon using mutant BK19 as a whole-cell catalyst, D-fructose was converted into GlcN with 65.32% conversion in 6 h, whereas the wild type only attained a conversion rate of 0.31% under the same conditions. Molecular docking and molecular dynamics simulations were implemented to provide insights into the mechanism underlying the enhanced activity of BK19. Importantly, the BsGlmS-BK19 variant specifically catalyzes D-fructose without the need for phosphorylated substrates, representing a significant advancement in GlcN biosynthesis.
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Affiliation(s)
- Zheng-Bing Guan
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China
| | - Xue-Ting Deng
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China
| | - Zi-Hao Zhang
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China
| | - Guo-Chao Xu
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China
| | - Wan-Li Cheng
- State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 430062, People's Republic of China
| | - Xiang-Ru Liao
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China
| | - Yu-Jie Cai
- The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, People's Republic of China
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2
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Wang Z, Zhang S, Xu Q, Li Z, Gu X, Wood K, García Sakai V, Wan Q, Chu XQ. Experimental Evidence for the Role of Dynamics in pH-Dependent Enzymatic Activity. J Phys Chem B 2024; 128:5814-5822. [PMID: 38726956 DOI: 10.1021/acs.jpcb.4c00219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
Enzymatic activity is heavily influenced by pH, but the rationale for the dynamical mechanism of pH-dependent enzymatic activity has not been fully understood. In this work, combined neutron scattering techniques, including quasielastic neutron scattering (QENS) and small angle neutron scattering (SANS), are used to study the structural and dynamic changes of a model enzyme, xylanase, under different pH and temperature environments. The QENS results reveal that xylanase at optimal pH exhibits faster relaxational dynamics and a lower energy barrier between conformational substates. The SANS results demonstrate that pH affects both xylanase's stability and monodispersity. Our findings indicate that enzymes have optimized stability and function under their optimal pH conditions, with both structure and dynamics being affected. The current study offers valuable insights into enzymatic functionality mechanisms, allowing for broad industrial applications.
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Affiliation(s)
- Zhixin Wang
- Graduate School of China Academy of Engineering Physics, Beijing 100193, China
| | - Shengkai Zhang
- Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, China
- Institute of Advanced Science Facilities, Shenzhen 518107, China
| | - Qin Xu
- College of Science, Nanjing Agricultural University, Nanjing 210095, China
| | - Zhihong Li
- College of Science, Nanjing Agricultural University, Nanjing 210095, China
| | - Xudong Gu
- Graduate School of China Academy of Engineering Physics, Beijing 100193, China
| | - Kathleen Wood
- Australian Nuclear Science and Technology Organization, Lucas Heights, NSW 2234, Australia
| | - Victoria García Sakai
- ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
| | - Qun Wan
- Jiangsu Provincial Key Lab for Solid Organic Waste Utilization, Key Lab of Organic-Based Fertilizers of China, Jiangsu Collaborative Innovation Center for Solid Organic Wastes, Educational Ministry Engineering Center of Resource-saving Fertilizer, Nanjing Agricultural University, Nanjing 210095, People's Republic of China
| | - Xiang-Qiang Chu
- Shenzhen Research Institute, City University of Hong Kong, Shenzhen 518057, China
- Department of Physics, City University of Hong Kong, Hong Kong 999077, China
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3
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Whittington C, Sharma A, Hill SG, Iavarone AT, Hoffman BM, Offenbacher AR. Impact of N-Glycosylation on Protein Structure and Dynamics Linked to Enzymatic C-H Activation in the M. oryzae Lipoxygenase. Biochemistry 2024; 63:1335-1346. [PMID: 38690768 DOI: 10.1021/acs.biochem.4c00109] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2024]
Abstract
Lipoxygenases (LOXs) from pathogenic fungi are potential therapeutic targets for defense against plant and select human diseases. In contrast to the canonical LOXs in plants and animals, fungal LOXs are unique in having appended N-linked glycans. Such important post-translational modifications (PTMs) endow proteins with altered structure, stability, and/or function. In this study, we present the structural and functional outcomes of removing or altering these surface carbohydrates on the LOX from the devastating rice blast fungus, M. oryzae, MoLOX. Alteration of the PTMs did notinfluence the active site enzyme-substrate ground state structures as visualized by electron-nuclear double resonance (ENDOR) spectroscopy. However, removal of the eight N-linked glycans by asparagine-to-glutamine mutagenesis nonetheless led to a change in substrate selectivity and an elevated activation energy for the reaction with substrate linoleic acid, as determined by kinetic measurements. Comparative hydrogen-deuterium exchange mass spectrometry (HDX-MS) analysis of wild-type and Asn-to-Gln MoLOX variants revealed a regionally defined impact on the dynamics of the arched helix that covers the active site. Guided by these HDX results, a single glycan sequon knockout was generated at position 72, and its comparative substrate selectivity from kinetics nearly matched that of the Asn-to-Gln variant. The cumulative data from model glyco-enzyme MoLOX showcase how the presence, alteration, or removal of even a single N-linked glycan can influence the structural integrity and dynamics of the protein that are linked to an enzyme's catalytic proficiency, while indicating that extensive glycosylation protects the enzyme during pathogenesis by protecting it from protease degradation.
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Affiliation(s)
- Chris Whittington
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Ajay Sharma
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - S Gage Hill
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Anthony T Iavarone
- California Institute for Quantitative Biosciences, Department of Chemistry, University of California, Berkeley, Berkeley, California 94720, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Adam R Offenbacher
- Department of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
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4
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Singh G, Austin A, Bai M, Bradshaw J, Hammann BA, Kabotso DEK, Lu Y. Study of the Effects of Remote Heavy Group Vibrations on the Temperature Dependence of Hydride Kinetic Isotope Effects of the NADH/NAD + Model Reactions. ACS OMEGA 2024; 9:20593-20600. [PMID: 38737086 PMCID: PMC11080011 DOI: 10.1021/acsomega.4c02383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/11/2024] [Revised: 04/06/2024] [Accepted: 04/11/2024] [Indexed: 05/14/2024]
Abstract
It has recently been observed that the temperature(T)-dependence of KIEs in H-tunneling reactions, characterized by isotopic activation energy difference (ΔEa = EaD - EaH), is correlated to the rigidity of the tunneling ready states (TRSs) in enzymes. A more rigid system with narrowly distributed H-donor-acceptor distances (DADs) at the TRSs gives rise to a weaker T-dependence of KIEs (i.e., a smaller ΔEa). Theoreticians have attempted to develop new H-tunneling models to explain this, but none has been universally accepted. In order to further understand the observations in enzymes and provide useful data to build new theoretical models, we have studied the electronic and solvent effects on ΔEa's for the hydride-tunneling reactions of NADH/NAD+ analogues. We found that a tighter charge-transfer (CT) complex system gives rises to a smaller ΔEa, consistent with the enzyme observations. In this paper, we use the remote heavy group (R) vibrational effects to mediate the system rigidity to study the rigidity-ΔEa relationship. The specific hypothesis is that slower vibrations of a heavier remote group would broaden the DAD distributions and increase the ΔEa value. Four NADH/NAD+ systems were studied in acetonitrile but most of such heavy group vibrations do not appear to significantly increase the ΔEa. The remote heavy group vibrations in these systems may have not affected the CT complexation rigidity to a degree that can significantly increase the DADs, and further, the ΔEa values.
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Affiliation(s)
- Grishma Singh
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Ava Austin
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Mingxuan Bai
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Joshua Bradshaw
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Blake A. Hammann
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | | | - Yun Lu
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
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5
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Ohler A, Taylor PE, Bledsoe JA, Iavarone AT, Gilbert NC, Offenbacher AR. Identification of the Thermal Activation Network in Human 15-Lipoxygenase-2: Divergence from Plant Orthologs and Its Relationship to Hydrogen Tunneling Activation Barriers. ACS Catal 2024; 14:5444-5457. [PMID: 38601784 PMCID: PMC11003420 DOI: 10.1021/acscatal.4c00439] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 03/05/2024] [Accepted: 03/13/2024] [Indexed: 04/12/2024]
Abstract
The oxidation of polyunsaturated fatty acids by lipoxygenases (LOXs) is initiated by a C-H cleavage step in which the hydrogen atom is transferred quantum mechanically (i.e., via tunneling). In these reactions, protein thermal motions facilitate the conversion of ground-state enzyme-substrate complexes to tunneling-ready configurations and are thus important for transferring energy from the solvent to the active site for the activation of catalysis. In this report, we employed temperature-dependent hydrogen-deuterium exchange mass spectrometry (TDHDX-MS) to identify catalytically linked, thermally activated peptides in a representative animal LOX, human epithelial 15-LOX-2. TDHDX-MS of wild-type 15-LOX-2 was compared to two active site mutations that retain structural stability but have increased activation energies (Ea) of catalysis. The Ea value of one variant, V427L, is implicated to arise from suboptimal substrate positioning by increased active-site side chain rotamer dynamics, as determined by X-ray crystallography and ensemble refinement. The resolved thermal network from the comparative Eas of TDHDX-MS between wild-type and V426A is localized along the front face of the 15-LOX-2 catalytic domain. The network contains a clustering of isoleucine, leucine, and valine side chains within the helical peptides. This thermal network of 15-LOX-2 is different in location, area, and backbone structure compared to a model plant lipoxygenase from soybean that exhibits a low Ea value of catalysis compared to the human ortholog. The presented data provide insights into the divergence of thermally activated protein motions in plant and animal LOXs and their relationships to the enthalpic barriers for facilitating hydrogen tunneling.
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Affiliation(s)
- Amanda Ohler
- Department
of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
| | - Paris E. Taylor
- Department
of Biological Sciences, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
| | - Jasmine A. Bledsoe
- Department
of Biological Sciences, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
| | - Anthony T. Iavarone
- QB3/Chemistry
Mass Spectrometry Facility, University of
California, Berkeley, Berkeley, California 94720, United States
| | - Nathaniel C. Gilbert
- Department
of Biological Sciences, Louisiana State
University, Baton
Rouge, Louisiana 70803, United States
| | - Adam R. Offenbacher
- Department
of Chemistry, East Carolina University, Greenville, North Carolina 27858, United States
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6
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Beach A, Adhikari P, Singh G, Song M, DeGroot N, Lu Y. Structural Effects on the Temperature Dependence of Hydride Kinetic Isotope Effects of the NADH/NAD + Model Reactions in Acetonitrile: Charge-Transfer Complex Tightness Is a Key. J Org Chem 2024; 89:3184-3193. [PMID: 38364859 PMCID: PMC10913049 DOI: 10.1021/acs.joc.3c02562] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 01/12/2024] [Accepted: 01/18/2024] [Indexed: 02/18/2024]
Abstract
It has recently frequently been found that the kinetic isotope effect (KIE) is independent of temperature (T) in H-tunneling reactions in enzymes but becomes dependent on T in their mutants. Many enzymologists found that the trend is related to different donor-acceptor distances (DADs) at tunneling-ready states (TRSs), which could be sampled by protein dynamics. That is, a more rigid system of densely populated short DADs gives rise to a weaker T dependence of KIEs. Theoreticians have attempted to develop H-tunneling theories to explain the observations, but none have been universally accepted. It is reasonable to assume that the DAD sampling concept, if it exists, applies to the H-transfer reactions in solution, as well. In this work, we designed NADH/NAD+ model reactions to investigate their structural effects on the T dependence of hydride KIEs in acetonitrile. Hammett correlations together with N-CH3/CD3 secondary KIEs were used to provide the electronic structure of the TRSs and thus the rigidity of their charge-transfer complexation vibrations. In all three pairs of reactions, a weaker T dependence of KIEs always corresponds to a steeper Hammett slope on the substituted hydride acceptors. It was found that a tighter/rigid charge-transfer complexation system corresponds with a weaker T dependence of KIEs, consistent with the observations in enzymes.
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Affiliation(s)
- Amanda Beach
- Department of Chemistry, Southern
Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Pratichhya Adhikari
- Department of Chemistry, Southern
Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Grishma Singh
- Department of Chemistry, Southern
Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Meimei Song
- Department of Chemistry, Southern
Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Nicholas DeGroot
- Department of Chemistry, Southern
Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
| | - Yun Lu
- Department of Chemistry, Southern
Illinois University Edwardsville, Edwardsville, Illinois 62026, United States
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7
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Borsley S, Gallagher JM, Leigh DA, Roberts BMW. Ratcheting synthesis. Nat Rev Chem 2024; 8:8-29. [PMID: 38102412 DOI: 10.1038/s41570-023-00558-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/02/2023] [Indexed: 12/17/2023]
Abstract
Synthetic chemistry has traditionally relied on reactions between reactants of high chemical potential and transformations that proceed energetically downhill to either a global or local minimum (thermodynamic or kinetic control). Catalysts can be used to manipulate kinetic control, lowering activation energies to influence reaction outcomes. However, such chemistry is still constrained by the shape of one-dimensional reaction coordinates. Coupling synthesis to an orthogonal energy input can allow ratcheting of chemical reaction outcomes, reminiscent of the ways that molecular machines ratchet random thermal motion to bias conformational dynamics. This fundamentally distinct approach to synthesis allows multi-dimensional potential energy surfaces to be navigated, enabling reaction outcomes that cannot be achieved under conventional kinetic or thermodynamic control. In this Review, we discuss how ratcheted synthesis is ubiquitous throughout biology and consider how chemists might harness ratchet mechanisms to accelerate catalysis, drive chemical reactions uphill and programme complex reaction sequences.
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Affiliation(s)
- Stefan Borsley
- Department of Chemistry, University of Manchester, Manchester, UK
| | | | - David A Leigh
- Department of Chemistry, University of Manchester, Manchester, UK.
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8
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Guevara L, Gouge M, Ohler A, Hill SG, Patel S, Offenbacher AR. Effect of solvent viscosity on the activation barrier of hydrogen tunneling in the lipoxygenase reaction. Arch Biochem Biophys 2023; 747:109740. [PMID: 37678425 DOI: 10.1016/j.abb.2023.109740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2023] [Revised: 08/22/2023] [Accepted: 09/05/2023] [Indexed: 09/09/2023]
Abstract
Hydrogen tunneling in enzyme reactions has played an important role in linking protein thermal motions to the chemical steps of catalysis. Lipoxygenases (LOXs) have served as model systems for such reactions, showcasing deep hydrogen tunneling mechanisms associated with enzymatic C-H bond cleavage from polyunsaturated fatty acids. Here, we examined the effect of solvent viscosity on the protein thermal motions associated with LOX catalysis using trehalose and glucose as viscogens. Kinetic analysis of the reaction of the paradigm plant orthologue, soybean lipoxygenase (SLO), with linoleic acid revealed no effect on the first-order rate constants, kcat, or activation energy, Ea. Further studies of SLO active site mutants displaying varying Eas, which have been used to probe catalytically relevant motions, likewise provided no evidence for viscogen-dependent motions. Kinetic analyses were extended to a representative fungal LOX from M. oryzae, MoLOX, and a human LOX, 15-LOX-2. While MoLOX behaved similarly to SLO, we show that viscogens inhibit 15-LOX-2 activity. The latter implicates viscogen sensitive, conformational motions in animal LOX reactions. The data provide insight into the role of water hydration layers in facilitating hydrogen (quantum) tunneling in LOX.
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Affiliation(s)
- Luis Guevara
- Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA
| | - Melissa Gouge
- Department of Chemistry and Biochemistry, Ohio Northern University, Ada, OH, 45810, USA
| | - Amanda Ohler
- Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA
| | - S Gage Hill
- Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA
| | - Soham Patel
- Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA
| | - Adam R Offenbacher
- Department of Chemistry, East Carolina University, Greenville, NC, 27858, USA.
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9
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Bai M, Pratap R, Salarvand S, Lu Y. Correlation of temperature dependence of hydride kinetic isotope effects with donor-acceptor distances in two solvents of different polarities. Org Biomol Chem 2023; 21:5090-5097. [PMID: 37278324 PMCID: PMC10339711 DOI: 10.1039/d3ob00718a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Recently observed nearly temperature (T)-independent kinetic isotope effects (KIEs) in wild-type enzymes and T-dependent KIEs in variants were used to suggest that H-tunneling in enzymes is assisted by the fast protein vibrations that help sample short donor-acceptor distances (DADs). This supports the recently proposed role of protein vibrations in DAD sampling catalysis. However, use of T-dependence of KIEs to suggest DAD sampling associated with protein vibrations is debated. We have formulated a hypothesis regarding the correlation and designed experiments in solution to investigate it. The hypothesis is, a more rigid system with shorter DADTRS's at the tunneling ready states (TRSs) gives rise to a weaker T-dependence of KIEs, i.e., a smaller ΔEa (= EaD - EaH). In a former work, the solvent effects of acetonitrile versus chloroform on the ΔEa of NADH/NAD+ model reactions were determined, and the DADPRC's of the productive reactant complexes (PRCs) were computed to substitute the DADTRS for the DADTRS-ΔEa correlation study. A smaller ΔEa was found in the more polar acetonitrile where the positively charged PRC is better solvated and has a shorter DADPRC, indirectly supporting the hypothesis. In this work, the TRS structures of different DADTRS's for the hydride tunneling reaction from 1,3-dimethyl-2-phenylimidazoline to 10-methylacridinium were computed. The N-CH3/CD3 secondary KIEs on both reactants were calculated and fitted to the observed values to find the DADTRS order in both solutions. It was found that the equilibrium DADTRS is shorter in acetonitrile than in chloroform. Results directly support the DADTRS-ΔEa correlation hypothesis as well as the explanation that links T-dependence of KIEs to DAD sampling catalysis in enzymes.
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Affiliation(s)
- Mingxuan Bai
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, USA.
| | - Rijal Pratap
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, USA.
| | - Sanaz Salarvand
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, USA.
| | - Yun Lu
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, Illinois 62026, USA.
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10
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Deng J, Cui Q. Second-Shell Residues Contribute to Catalysis by Predominately Preorganizing the Apo State in PafA. J Am Chem Soc 2023; 145:11333-11347. [PMID: 37172218 PMCID: PMC10810092 DOI: 10.1021/jacs.3c02423] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Residues beyond the first coordination shell are often observed to make considerable cumulative contributions in enzymes. Due to typically indirect perturbations of multiple physicochemical properties of the active site, however, their individual and specific roles in enzyme catalysis and disease-causing mutations remain difficult to predict and understand at the molecular level. Here we analyze the contributions of several second-shell residues in phosphate-irrepressible alkaline phosphatase of flavobacterium (PafA), a representative system as one of the most efficient enzymes. By adopting a multifaceted approach that integrates quantum-mechanical/molecular-mechanical free energy computations, molecular-mechanical molecular dynamics simulations, and density functional theory cluster model calculations, we probe the rate-limiting phosphoryl transfer step and structural properties of all relevant enzyme states. In combination with available experimental data, our computational results show that mutations of the studied second-shell residues impact catalytic efficiency mainly by perturbation of the apo state and therefore substrate binding, while they do not affect the ground state or alter the nature of phosphoryl transfer transition state significantly. Several second-shell mutations also modulate the active site hydration level, which in turn influences the energetics of phosphoryl transfer. These mechanistic insights also help inform strategies that may improve the efficiency of enzyme design and engineering by going beyond the current focus on the first coordination shell.
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Affiliation(s)
- Jiahua Deng
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
| | - Qiang Cui
- Department of Chemistry, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
- Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215, United States
- Department of Biomedical Engineering, Boston University, 44 Cummington Mall, Boston, Massachusetts 02215, United States
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11
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Adhikari P, Song M, Bai M, Rijal P, DeGroot N, Lu Y. Solvent Effects on the Temperature Dependence of Hydride Kinetic Isotope Effects: Correlation to the Donor-Acceptor Distances. J Phys Chem A 2022; 126:7675-7686. [PMID: 36228057 DOI: 10.1021/acs.jpca.2c06065] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein structural effects on the temperature (T) dependence of kinetic isotope effects (KIEs) in H-tunneling reactions have recently been used to discuss about the role of enzyme thermal motions in catalysis. Frequently observed nearly T-independent KIEs in the wild-type enzymes and T-dependent KIEs in variants suggest that H-tunneling in the former is assisted by the naturally evolved protein constructive vibrations that help sample short donor-acceptor distances (DADs) needed. This explanation that correlates the T-dependence of KIEs with DAD sampling has been highly debated as simulations following other H-tunneling models sometimes gave alternative explanations. In this paper, solvent effects on the T-dependence of KIEs of two hydride tunneling reactions of NADH/NAD+ analogues (represented by ΔEa = EaD - EaH) were determined in attempts to replicate the observations in enzymes and test the protein vibration-assisted DAD sampling concept. Effects of selected aprotic solvents on the DADPRC's of the productive reactant complexes (PRCs) and the DADTRS's of the activated tunneling ready states (TRSs) were obtained through computations and analyses of the kinetic data, including 2° KIEs, respectively. A weaker T-dependence of KIEs (i.e., smaller ΔEa) was found in a more polar aprotic solvent in which the system has a shorter average DADPRC and DADTRS. Further results show that a charge-transfer (CT) complexation made of a stronger donor/acceptor gives rise to a smaller ΔEa. Overall, the shorter and less broadly distributed DADs resulting from the stronger CT complexation vibrations give rise to a smaller ΔEa. Our results appear to support the explanation that links the T-dependence of KIEs to the donor-acceptor rigidity in enzymes.
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Affiliation(s)
- Pratichhya Adhikari
- Department of Chemistry, Southern Illinois University, Edwardsville, Edwardsville, Illinois 62026, United States
| | - Meimei Song
- Department of Chemistry, Southern Illinois University, Edwardsville, Edwardsville, Illinois 62026, United States
| | - Mingxuan Bai
- Department of Chemistry, Southern Illinois University, Edwardsville, Edwardsville, Illinois 62026, United States
| | - Pratap Rijal
- Department of Chemistry, Southern Illinois University, Edwardsville, Edwardsville, Illinois 62026, United States
| | - Nicholas DeGroot
- Department of Chemistry, Southern Illinois University, Edwardsville, Edwardsville, Illinois 62026, United States
| | - Yun Lu
- Department of Chemistry, Southern Illinois University, Edwardsville, Edwardsville, Illinois 62026, United States
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12
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Gao S, Klinman JP. Functional roles of enzyme dynamics in accelerating active site chemistry: Emerging techniques and changing concepts. Curr Opin Struct Biol 2022; 75:102434. [PMID: 35872562 PMCID: PMC9901422 DOI: 10.1016/j.sbi.2022.102434] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/15/2022] [Accepted: 06/21/2022] [Indexed: 02/08/2023]
Abstract
With the growing acceptance of the contribution of protein conformational ensembles to enzyme catalysis and regulation, research in the field of protein dynamics has shifted toward an understanding of the atomistic properties of protein dynamical networks and the mechanisms and time scales that control such behavior. A full description of an enzymatic reaction coordinate is expected to extend beyond the active site and include site-specific networks that communicate with the protein/water interface. Advances in experimental tools for the spatial resolution of thermal activation pathways are being complemented by biophysical methods for visualizing dynamics in real time. An emerging multidimensional model integrates the impacts of bound substrate/effector on the distribution of protein substates that are in rapid equilibration near room temperature with reaction-specific protein embedded heat transfer conduits.
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Affiliation(s)
- Shuaihua Gao
- Department of Chemistry, University of California, Berkeley, CA, 94720, United States; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, United States. https://twitter.com/S_H_Gao
| | - Judith P Klinman
- Department of Chemistry, University of California, Berkeley, CA, 94720, United States; California Institute for Quantitative Biosciences, University of California, Berkeley, CA, 94720, United States; Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720, United States.
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13
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Abstract
Many enzymes that show a large specificity in binding the enzymatic transition state with a higher affinity than the substrate utilize substrate binding energy to drive protein conformational changes to form caged substrate complexes. These protein cages provide strong stabilization of enzymatic transition states. Using part of the substrate binding energy to drive the protein conformational change avoids a similar strong stabilization of the Michaelis complex and irreversible ligand binding. A seminal step in the development of modern enzyme catalysts was the evolution of enzymes that couple substrate binding to a conformational change. These include enzymes that function in glycolysis (triosephosphate isomerase), the biosynthesis of lipids (glycerol phosphate dehydrogenase), the hexose monophosphate shunt (6-phosphogluconate dehydrogenase), and the mevalonate pathway (isopentenyl diphosphate isomerase), catalyze the final step in the biosynthesis of pyrimidine nucleotides (orotidine monophosphate decarboxylase), and regulate the cellular levels of adenine nucleotides (adenylate kinase). The evolution of enzymes that undergo ligand-driven conformational changes to form active protein-substrate cages is proposed to proceed by selection of variants, in which the selected side chain substitutions destabilize a second protein conformer that shows compensating enhanced binding interactions with the substrate. The advantages inherent to enzymes that incorporate a conformational change into the catalytic cycle provide a strong driving force for the evolution of flexible protein folds such as the TIM barrel. The appearance of these folds represented a watershed event in enzyme evolution that enabled the rapid propagation of enzyme activities within enzyme superfamilies.
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Affiliation(s)
- John P Richard
- Department of Chemistry, University at Buffalo, the State University of New York, Buffalo, New York 14260-3000, United States
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14
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Rapp C, Nidetzky B. Hydride Transfer Mechanism of Enzymatic Sugar Nucleotide C2 Epimerization Probed with a Loose-Fit CDP-Glucose Substrate. ACS Catal 2022; 12:6816-6830. [PMID: 35747200 PMCID: PMC9207888 DOI: 10.1021/acscatal.2c00257] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Revised: 05/12/2022] [Indexed: 11/29/2022]
Abstract
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Transient oxidation–reduction
through hydride transfer with
tightly bound NAD coenzyme is used by a large class of sugar nucleotide
epimerases to promote configurational inversion of carbon stereocenters
in carbohydrate substrates. A requirement for the epimerases to coordinate
hydride abstraction and re-addition with substrate rotation in the
binding pocket poses a challenge for dynamical protein conformational
selection linked to enzyme catalysis. Here, we studied the thermophilic
C2 epimerase from Thermodesulfatator atlanticus (TaCPa2E) in combination with a slow CDP-glucose
substrate (kcat ≈ 1.0 min–1; 60 °C) to explore the sensitivity of the enzymatic hydride
transfer toward environmental fluctuations affected by temperature
(20–80 °C). We determined noncompetitive primary kinetic
isotope effects (KIE) due to 2H at the glucose C2 and showed
that a normal KIE on the kcat (Dkcat) reflects isotope sensitivity of
the hydrogen abstraction to enzyme-NAD+ in a rate-limiting
transient oxidation. The Dkcat peaked at 40 °C was 6.1 and decreased to 2.1 at low (20 °C)
and 3.3 at high temperature (80 °C). The temperature profiles
for kcat with the 1H and 2H substrate showed a decrease in the rate below a dynamically
important breakpoint (∼40 °C), suggesting an equilibrium
shift to an impaired conformational landscape relevant for catalysis
in the low-temperature region. Full Marcus-like model fits of the
rate and KIE profiles provided evidence for a high-temperature reaction
via low-frequency conformational sampling associated with a broad
distribution of hydride donor–acceptor distances (long-distance
population centered at 3.31 ± 0.02 Å), only poorly suitable
for quantum mechanical tunneling. Collectively, dynamical characteristics
of TaCPa2E-catalyzed hydride transfer during transient
oxidation of CDP-glucose reveal important analogies to mechanistically
simpler enzymes such as alcohol dehydrogenase and dihydrofolate reductase.
A loose-fit substrate (in TaCPa2E) resembles structural
variants of these enzymes by extensive dynamical sampling to balance
conformational flexibility and catalytic efficiency.
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Affiliation(s)
- Christian Rapp
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 10-12/1, 8010 Graz, Austria
| | - Bernd Nidetzky
- Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 10-12/1, 8010 Graz, Austria
- Austrian Centre of Industrial Biotechnology (ACIB), Petersgasse 14, 8010 Graz, Austria
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15
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Schafer JW, Chen X, Schwartz SD. Engineered Tryptophan Synthase Balances Equilibrium Effects and Fast Dynamic Effects. ACS Catal 2022; 12:913-922. [PMID: 35719741 PMCID: PMC9202816 DOI: 10.1021/acscatal.1c03913] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Creating efficient and stable enzymes for catalysis in pharmaceutical and industrial laboratories is an important research goal. Arnold et al. used directed evolution to engineer a natural tryptophan synthase to create a mutant that is operable under laboratory conditions without the need for a natural allosteric effector. The use of directed evolution allows researchers to improve enzymes without understanding the structure-activity relationship. Here, we present a transition path sampling study of a key chemical transformation in the tryptophan synthase catalytic cycle. We observed that while directed evolution does mimic the natural allosteric effect from a stability perspective, fast protein dynamics associated with chemistry has been dramatically altered. This work provides further evidence of the role of protein dynamics in catalysis and clearly demonstrates the multifaceted complexity of mutations associated with protein engineering. This study also demonstrates a fascinating contrast between allosteric and stand-alone functions at the femtosecond time scale.
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Affiliation(s)
- Joseph W Schafer
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Xi Chen
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Steven D Schwartz
- Department of Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
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16
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Li J, Lin J, Kohen A, Singh P, Francis K, Cheatum CM. Evolution of Optimized Hydride Transfer Reaction and Overall Enzyme Turnover in Human Dihydrofolate Reductase. Biochemistry 2021; 60:3822-3828. [PMID: 34875176 PMCID: PMC8697555 DOI: 10.1021/acs.biochem.1c00558] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Evolution of dihydrofolate
reductase (DHFR) has been studied using
the enzyme from Escherichia coli DHFR
(ecDHFR) as a model, but less studies have used the enzyme from Homo sapiens DHFR (hsDHFR). Each enzyme maintains
a short and narrow distribution of hydride donor-acceptor distances
(DAD) at the tunneling ready state (TRS). Evolution of the enzyme
was previously studied in ecDHFR where three key sites were identified
as important to the catalyzed reaction. The corresponding sites in
hsDHFR are F28, 62-PEKN, and 26-PPLR. Each of these sites was studied
here through the creation of mutant variants of the enzyme and measurements
of the temperature dependence of the intrinsic kinetic isotope effects
(KIEs) on the reaction. F28 is mutated first to M (F28M) and then
to the L of the bacterial enzyme (F28L). The KIEs of the F28M variant
are larger and more temperature-dependent than wild-type (WT), suggesting
a broader and longer average DAD at the TRS. To more fully mimic ecDHFR,
we also study a triple mutant of the human enzyme (F32L-PP26N-PEKN62G).
Remarkably, the intrinsic KIEs, while larger in magnitude, are temperature-independent
like the WT enzymes. We also construct deletion mutations of hsDHFR
removing both the 62-PEKN and 26-PPLR sequences. The results mirror
those described previously for insertion mutants of ecDHFR. Taken
together, these results suggest a balancing act during DHFR evolution
between achieving an optimal TRS for hydride transfer and preventing
product inhibition arising from the different intercellular pools
of NADPH and NADP+ in prokaryotic and eukaryotic cells.
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Affiliation(s)
- Jiayue Li
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Jennifer Lin
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Amnon Kohen
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Priyanka Singh
- Department of Chemistry, University of Iowa, Iowa City, Iowa 52242, United States
| | - Kevin Francis
- Texas A&M University-Kingsville, Kingsville, Texas 78363, United States
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