1
|
Sobrado P, Neira JL. Paul F. Fitzpatrick: A life of editorial duties and elucidating the mechanism of enzyme action. Arch Biochem Biophys 2023; 742:109635. [PMID: 37209767 DOI: 10.1016/j.abb.2023.109635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 05/09/2023] [Indexed: 05/22/2023]
Affiliation(s)
- Pablo Sobrado
- Department of Biochemistry, Virginia Tech, 360 West Campus Drive, Blacksburg, VA, 24061, USA.
| | - José Luis Neira
- IDIBE, Universidad Miguel Hernández, 03202, Elche, Alicante, Spain; Instituto de Biocomputación y Física de Sistemas Complejos (BIFI) - Unidad Mixta GBsC-CSIC-BIFI, Universidad de Zaragoza, 50018, Zaragoza, Spain.
| |
Collapse
|
2
|
Ma S, Ludwig R. Direct Electron Transfer of Enzymes Facilitated by Cytochromes. ChemElectroChem 2019; 6:958-975. [PMID: 31008015 PMCID: PMC6472588 DOI: 10.1002/celc.201801256] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 11/12/2018] [Indexed: 01/03/2023]
Abstract
The direct electron transfer (DET) of enzymes has been utilized to develop biosensors and enzymatic biofuel cells on micro- and nanostructured electrodes. Whereas some enzymes exhibit direct electron transfer between their active-site cofactor and an electrode, other oxidoreductases depend on acquired cytochrome domains or cytochrome subunits as built-in redox mediators. The physiological function of these cytochromes is to transfer electrons between the active-site cofactor and a redox partner protein. The exchange of the natural electron acceptor/donor by an electrode has been demonstrated for several cytochrome carrying oxidoreductases. These multi-cofactor enzymes have been applied in third generation biosensors to detect glucose, lactate, and other analytes. This review investigates and classifies oxidoreductases with a cytochrome domain, enzyme complexes with a cytochrome subunit, and covers designed cytochrome fusion enzymes. The structurally and electrochemically best characterized proponents from each enzyme class carrying a cytochrome, that is, flavoenzymes, quinoenzymes, molybdenum-cofactor enzymes, iron-sulfur cluster enzymes, and multi-haem enzymes, are featured, and their biochemical, kinetic, and electrochemical properties are compared. The cytochromes molecular and functional properties as well as their contribution to the interdomain electron transfer (IET, between active-site and cytochrome) and DET (between cytochrome and electrode) with regard to the achieved current density is discussed. Protein design strategies for cytochrome-fused enzymes are reviewed and the limiting factors as well as strategies to overcome them are outlined.
Collapse
Affiliation(s)
- Su Ma
- Biocatalysis and Biosensing Laboratory Department of Food Science and TechnologyBOKU – University of Natural Resources and Life SciencesMuthgasse 181190ViennaAustria
| | - Roland Ludwig
- Biocatalysis and Biosensing Laboratory Department of Food Science and TechnologyBOKU – University of Natural Resources and Life SciencesMuthgasse 181190ViennaAustria
| |
Collapse
|
3
|
A Bacterial Multidomain NAD-Independent d-Lactate Dehydrogenase Utilizes Flavin Adenine Dinucleotide and Fe-S Clusters as Cofactors and Quinone as an Electron Acceptor for d-Lactate Oxidization. J Bacteriol 2017; 199:JB.00342-17. [PMID: 28847921 DOI: 10.1128/jb.00342-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Accepted: 08/22/2017] [Indexed: 11/20/2022] Open
Abstract
Bacterial membrane-associated NAD-independent d-lactate dehydrogenase (Fe-S d-iLDH) oxidizes d-lactate into pyruvate. A sequence analysis of the enzyme reveals that it contains an Fe-S oxidoreductase domain in addition to a flavin adenine dinucleotide (FAD)-containing dehydrogenase domain, which differs from other typical d-iLDHs. Fe-S d-iLDH from Pseudomonas putida KT2440 was purified as a His-tagged protein and characterized in detail. This monomeric enzyme exhibited activities with l-lactate and several d-2-hydroxyacids. Quinone was shown to be the preferred electron acceptor of the enzyme. The two domains of the enzyme were then heterologously expressed and purified separately. The Fe-S cluster-binding motifs predicted by sequence alignment were preliminarily verified by site-directed mutagenesis of the Fe-S oxidoreductase domain. The FAD-containing dehydrogenase domain retained 2-hydroxyacid-oxidizing activity, although it decreased compared to the full Fe-S d-iLDH. Compared to the intact enzyme, the FAD-containing dehydrogenase domain showed increased catalytic efficiency with cytochrome c as the electron acceptor, but it completely lost the ability to use coenzyme Q10 Additionally, the FAD-containing dehydrogenase domain was no longer associated with the cell membrane, and it could not support the utilization of d-lactate as a carbon source. Based on the results obtained, we conclude that the Fe-S oxidoreductase domain functions as an electron transfer component to facilitate the utilization of quinone as an electron acceptor by Fe-S d-iLDH, and it helps the enzyme associate with the cell membrane. These functions make the Fe-S oxidoreductase domain crucial for the in vivo d-lactate utilization function of Fe-S d-iLDH.IMPORTANCE Lactate metabolism plays versatile roles in most domains of life. Lactate utilization processes depend on certain enzymes to oxidize lactate to pyruvate. In recent years, novel bacterial lactate-oxidizing enzymes have been continually reported, including the unique NAD-independent d-lactate dehydrogenase that contains an Fe-S oxidoreductase domain besides the typical flavin-containing domain (Fe-S d-iLDH). Although Fe-S d-iLDH is widely distributed among bacterial species, the investigation of it is insufficient. Fe-S d-iLDH from Pseudomonas putida KT2440, which is the major d-lactate-oxidizing enzyme for the strain, might be a representative of this type of enzyme. A study of it will be helpful in understanding the detailed mechanisms underlying the lactate utilization processes.
Collapse
|
4
|
Aboelnga MM, Hayward JJ, Gauld JW. Enzymatic Post-Transfer Editing Mechanism of E. coli Threonyl-tRNA Synthetase (ThrRS): A Molecular Dynamics (MD) and Quantum Mechanics/Molecular Mechanics (QM/MM) Investigation. ACS Catal 2017. [DOI: 10.1021/acscatal.7b01554] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Mohamed M. Aboelnga
- Department
of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
- Department
of Chemistry, Faculty of Science, University of Damietta, New Damietta, Damietta Governorate 34511, Egypt
| | - John J. Hayward
- Department
of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario N9B 3P4, Canada
| | | |
Collapse
|
5
|
Elhoul MB, Machillot P, Benoît M, Lederer F. Translational misreading, amino acid misincorporation and misinterpretations. The case of the flavocytochrome b 2 H373Q variant. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1865:353-358. [PMID: 28007443 DOI: 10.1016/j.bbapap.2016.12.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Revised: 11/24/2016] [Accepted: 12/16/2016] [Indexed: 11/19/2022]
Abstract
Amino acid misincorporation during protein synthesis occurs naturally at a low level. Protein sequence errors, depending on the level and the nature of the misincorporation, can have various consequences. When site-directed mutagenesis is used as a tool for understanding the role of a side chain in enzyme catalysis, misincorporation in a variant with intrinsically low activity may lead to misinterpretations concerning the enzyme mechanism. We report here one more example of such a problem, dealing with flavocytochrome b2 (Fcb2), a lactate dehydrogenase, member of a family of FMN-dependent L-2-hydroxy acid oxidizing enzymes. Two papers have described the properties of the Fcb2 catalytic base H373Q variant, each one using a different expression system with the same base change for the mutation. The two papers found similar apparent kinetic parameters. But the first one demonstrated the existence of a low level of histidine misincorporation, which led to an important correction of the variant residual activity (Gaume et al. (1995) Biochimie, 77, 621). The second paper did not investigate the possibility of a misincorporation (Tsai et al. (2007) Biochemistry, 46, 7844). The two papers had different mechanistic conclusions. We show here that in this case the misincorporation does not depend on the expression system. We bring the proof that Tsai et al. (2007) were led to an erroneous mechanistic conclusion for having missed the phenomenon as well as for having misinterpreted the crystal structure of the variant. This work is another illustration of the caution one should exercise when characterizing enzyme variants with low activity.
Collapse
Affiliation(s)
- Mouna Ben Elhoul
- Laboratoire de Chimie Physique, CNRS UMR 8000, Faculté des Sciences, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Paul Machillot
- Laboratoire de Chimie Physique, CNRS UMR 8000, Faculté des Sciences, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Mireille Benoît
- Laboratoire de Chimie Physique, CNRS UMR 8000, Faculté des Sciences, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France
| | - Florence Lederer
- Laboratoire de Chimie Physique, CNRS UMR 8000, Faculté des Sciences, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France.
| |
Collapse
|
6
|
Conformational flexibility related to enzyme activity: evidence for a dynamic active-site gatekeeper function of Tyr(215) in Aerococcus viridans lactate oxidase. Sci Rep 2016; 6:27892. [PMID: 27302031 PMCID: PMC4908395 DOI: 10.1038/srep27892] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2016] [Accepted: 05/26/2016] [Indexed: 01/15/2023] Open
Abstract
L-Lactate oxidase (LOX) belongs to a large family of flavoenzymes that catalyze oxidation of α-hydroxy acids. How in these enzymes the protein structure controls reactivity presents an important but elusive problem. LOX contains a prominent tyrosine in the substrate binding pocket (Tyr(215) in Aerococcus viridans LOX) that is partially responsible for securing a flexible loop which sequesters the active site. To characterize the role of Tyr(215), effects of substitutions of the tyrosine (Y215F, Y215H) were analyzed kinetically, crystallographically and by molecular dynamics simulations. Enzyme variants showed slowed flavin reduction and oxidation by up to 33-fold. Pyruvate release was also decelerated and in Y215F, it was the slowest step overall. A 2.6-Å crystal structure of Y215F in complex with pyruvate shows the hydrogen bond between the phenolic hydroxyl and the keto oxygen in pyruvate is replaced with a potentially stronger hydrophobic interaction between the phenylalanine and the methyl group of pyruvate. Residues 200 through 215 or 216 appear to be disordered in two of the eight monomers in the asymmetric unit suggesting that they function as a lid controlling substrate entry and product exit from the active site. Substitutions of Tyr(215) can thus lead to a kinetic bottleneck in product release.
Collapse
|
7
|
Lederer F, Vignaud C, North P, Bodevin S. Trifluorosubstrates as mechanistic probes for an FMN-dependent l-2-hydroxy acid-oxidizing enzyme. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1215-1221. [PMID: 27155230 DOI: 10.1016/j.bbapap.2016.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 03/13/2016] [Revised: 04/17/2016] [Accepted: 05/03/2016] [Indexed: 11/29/2022]
Abstract
A controversy exists with respect to the mechanism of l-2-hydroxy acid oxidation by members of a family of FMN-dependent enzymes. A so-called carbanion mechanism was initially proposed, in which the active site histidine abstracts the substrate α-hydrogen as a proton, followed by electron transfer from the carbanion to the flavin. But an alternative mechanism was not incompatible with some results, a mechanism in which the active site histidine instead picks up the substrate hydroxyl proton and a hydride transfer occurs. Even though more recent experiments ruling out such a mechanism were published (Rao & Lederer (1999) Protein Science 7, 1531-1537), a few authors have subsequently interpreted their results with variant enzymes in terms of a hydride transfer. In the present work, we analyse the reactivity of trifluorolactate, a substrate analogue, with the flavocytochrome b2 (Fcb2) flavodehydrogenase domain, compared to its reactivity with an NAD-dependent lactate dehydrogenase (LDH), for which this compound is known to be an inhibitor (Pogolotti & Rupley (1973) Biochem. Biophys. Res. Commun, 55, 1214-1219). Indeed, electron attraction by the three fluorine atoms should make difficult the removal of the α-H as a hydride. We also analyse the reactivity of trifluoropyruvate with the FMN- and NAD-dependent enzymes. The results substantiate a different effect of the fluorine substituents on the two enzymes compared to their normal substrates. In the discussion we analyse the conclusions of recent papers advocating a hydride transfer mechanism for the family of l-2-hydroxy acid oxidizing FMN-dependent enzymes.
Collapse
Affiliation(s)
- Florence Lederer
- Laboratoire d'Enzymologie, UPR 9063, CNRS, 91198 Gif-sur-Yvette Cedex, France; Laboratoire de Chimie Physique, CNRS UMR 8000, Université Paris-Sud, Université Paris-Saclay, 91405 Orsay Cedex, France.
| | - Caroline Vignaud
- Laboratoire d'Enzymologie, UPR 9063, CNRS, 91198 Gif-sur-Yvette Cedex, France
| | - Paul North
- Laboratoire d'Enzymologie, UPR 9063, CNRS, 91198 Gif-sur-Yvette Cedex, France
| | - Sabrina Bodevin
- Laboratoire d'Enzymologie, UPR 9063, CNRS, 91198 Gif-sur-Yvette Cedex, France
| |
Collapse
|
8
|
Dellero Y, Jossier M, Schmitz J, Maurino VG, Hodges M. Photorespiratory glycolate-glyoxylate metabolism. JOURNAL OF EXPERIMENTAL BOTANY 2016; 67:3041-52. [PMID: 26994478 DOI: 10.1093/jxb/erw090] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Photorespiration is one of the major carbon metabolism pathways in oxygen-producing photosynthetic organisms. This pathway recycles 2-phosphoglycolate (2-PG), a toxic metabolite, to 3-phosphoglycerate when ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) uses oxygen instead of carbon dioxide. The photorespiratory cycle is in competition with photosynthetic CO2 fixation and it is accompanied by carbon, nitrogen and energy losses. Thus, photorespiration has become a target to improve crop yields. Moreover, during the photorespiratory cycle intermediate metabolites that are toxic to Calvin-Benson cycle and RuBisCO activities, such as 2-PG, glycolate and glyoxylate, are produced. Thus, the presence of an efficient 2-PG/glycolate/glyoxylate 'detoxification' pathway is required to ensure normal development of photosynthetic organisms. Here we review our current knowledge concerning the enzymes that carry out the glycolate-glyoxylate metabolic steps of photorespiration from glycolate production in the chloroplasts to the synthesis of glycine in the peroxisomes. We describe the properties of the proteins involved in glycolate-glyoxylate metabolism in Archaeplastida and the phenotypes observed when knocking down/out these specific photorespiratory players. Advances in our understanding of the regulation of glycolate-glyoxylate metabolism are highlighted.
Collapse
Affiliation(s)
- Younès Dellero
- Institut of Plant Sciences Paris-Saclay, Université Paris-Sud, CNRS, INRA, Université d'Evry, Université Paris Diderot, Université Paris-Saclay, Bât 630, 91405 Orsay Cedex, France
| | - Mathieu Jossier
- Institut of Plant Sciences Paris-Saclay, Université Paris-Sud, CNRS, INRA, Université d'Evry, Université Paris Diderot, Université Paris-Saclay, Bât 630, 91405 Orsay Cedex, France
| | - Jessica Schmitz
- Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences (CEPLAS), Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Veronica G Maurino
- Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, and Cluster of Excellence on Plant Sciences (CEPLAS), Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Michael Hodges
- Institut of Plant Sciences Paris-Saclay, Université Paris-Sud, CNRS, INRA, Université d'Evry, Université Paris Diderot, Université Paris-Saclay, Bât 630, 91405 Orsay Cedex, France
| |
Collapse
|
9
|
Dellero Y, Mauve C, Boex-Fontvieille E, Flesch V, Jossier M, Tcherkez G, Hodges M. Experimental evidence for a hydride transfer mechanism in plant glycolate oxidase catalysis. J Biol Chem 2014; 290:1689-98. [PMID: 25416784 DOI: 10.1074/jbc.m114.618629] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In plants, glycolate oxidase is involved in the photorespiratory cycle, one of the major fluxes at the global scale. To clarify both the nature of the mechanism and possible differences in glycolate oxidase enzyme chemistry from C3 and C4 plant species, we analyzed kinetic parameters of purified recombinant C3 (Arabidopsis thaliana) and C4 (Zea mays) plant enzymes and compared isotope effects using natural and deuterated glycolate in either natural or deuterated solvent. The (12)C/(13)C isotope effect was also investigated for each plant glycolate oxidase protein by measuring the (13)C natural abundance in glycolate using natural or deuterated glycolate as a substrate. Our results suggest that several elemental steps were associated with an hydrogen/deuterium isotope effect and that glycolate α-deprotonation itself was only partially rate-limiting. Calculations of commitment factors from observed kinetic isotope effect values support a hydride transfer mechanism. No significant differences were seen between C3 and C4 enzymes.
Collapse
Affiliation(s)
- Younès Dellero
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Caroline Mauve
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France, Plateforme Métabolisme-Métabolome, Saclay Plant Sciences, Institut de Biologie des Plantes, Bâtiment 630, 91405 Orsay Cedex, France, and
| | - Edouard Boex-Fontvieille
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Valérie Flesch
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Mathieu Jossier
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France
| | - Guillaume Tcherkez
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France, Plateforme Métabolisme-Métabolome, Saclay Plant Sciences, Institut de Biologie des Plantes, Bâtiment 630, 91405 Orsay Cedex, France, and Institut Universitaire de France, 103 Boulevard Saint-Michel, 75005 Paris, France
| | - Michael Hodges
- From the Institut de Biologie des Plantes, CNRS UMR8618, Saclay Plant Sciences, Bâtiment 630, Université Paris Sud, 91405 Orsay Cedex, France,
| |
Collapse
|
10
|
Jiang T, Gao C, Ma C, Xu P. Microbial lactate utilization: enzymes, pathogenesis, and regulation. Trends Microbiol 2014; 22:589-99. [PMID: 24950803 DOI: 10.1016/j.tim.2014.05.008] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2014] [Revised: 05/21/2014] [Accepted: 05/23/2014] [Indexed: 11/17/2022]
Abstract
Lactate utilization endows microbes with the ability to use lactate as a carbon source. Lactate oxidizing enzymes play key roles in the lactate utilization pathway. Various types of these enzymes have been characterized, but novel ones remain to be identified. Lactate determination techniques and biocatalysts have been developed based on these enzymes. Lactate utilization has also been found to induce pathogenicity of several microbes, and the mechanisms have been investigated. More recently, studies on the structure and organization of operons of lactate utilization have been carried out. This review focuses on the recent progress and future perspectives in understanding microbial lactate utilization.
Collapse
Affiliation(s)
- Tianyi Jiang
- State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China; State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, People's Republic of China; School of Municipal and Environmental Engineering, Shandong Jianzhu University, Jinan 250101, People's Republic of China
| | - Chao Gao
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, People's Republic of China
| | - Cuiqing Ma
- State Key Laboratory of Microbial Technology, Shandong University, Jinan 250100, People's Republic of China.
| | - Ping Xu
- State Key Laboratory of Microbial Metabolism and School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
| |
Collapse
|
11
|
Pozzi MH, Fitzpatrick PF. A lysine conserved in the monoamine oxidase family is involved in oxidation of the reduced flavin in mouse polyamine oxidase. Arch Biochem Biophys 2010; 498:83-8. [PMID: 20417173 PMCID: PMC2880204 DOI: 10.1016/j.abb.2010.04.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 04/19/2010] [Accepted: 04/20/2010] [Indexed: 10/19/2022]
Abstract
Lysine 315 of mouse polyamine amine oxidase corresponds to a lysine residue that is conserved in the flavoprotein amine oxidases of the monoamine oxidase structural family. In several structures, this lysine residue forms a hydrogen bond to a water molecule that is hydrogen-bonded to the flavin N(5). Mutation of Lys315 in polyamine oxidase to methionine was previously shown to have no effect on the kinetics of the reductive half-reaction of the enzyme (M. Henderson Pozzi, V. Gawandi, P.F. Fitzpatrick, Biochemistry 48 (2009) 1508-1516). In contrast, the mutation does affect steps in the oxidative half-reaction. The k(cat) value is unaffected by the mutation; this kinetic parameter likely reflects product release. At pH 10, the k(cat)/K(m) value for oxygen is 25-fold lower in the mutant enzyme. The k(cat)/K(O2) value is pH-dependent for the wild-type enzyme, decreasing below a pK(a) of 7.0, while this kinetic parameter for the mutant enzyme is pH-independent. This is consistent with the neutral form of Lys315 being required for more rapid flavin oxidation. The solvent isotope effect on the k(cat)/K(O2) value increases from 1.4 in the wild-type enzyme to 1.9 in the mutant protein, and the solvent inventory changes from linear to bowed. The effects of the mutation can be explained by the lysine orienting the bridging water so that it can accept the proton from the flavin N(5) during flavin oxidation. In the mutant enzyme the lysine amine would be replaced by a water chain.
Collapse
Affiliation(s)
| | - Paul F. Fitzpatrick
- Department of Biochemistry and Center for Biomedical Neuroscience, University of Texas Health Science Center at San Antonio, San Antonio TX 78229-3900
| |
Collapse
|
12
|
Mowat CG, Gazur B, Campbell LP, Chapman SK. Flavin-containing heme enzymes. Arch Biochem Biophys 2010; 493:37-52. [DOI: 10.1016/j.abb.2009.10.005] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2009] [Revised: 10/13/2009] [Accepted: 10/13/2009] [Indexed: 11/25/2022]
|
13
|
Pennati A, Gadda G. Involvement of ionizable groups in catalysis of human liver glycolate oxidase. J Biol Chem 2009; 284:31214-22. [PMID: 19758989 PMCID: PMC2781520 DOI: 10.1074/jbc.m109.040063] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2009] [Revised: 09/04/2009] [Indexed: 11/06/2022] Open
Abstract
Glycolate oxidase is a flavin-dependent, peroxisomal enzyme that oxidizes alpha-hydroxy acids to the corresponding alpha-keto acids, with reduction of oxygen to H(2)O(2). In plants, the enzyme participates in photorespiration. In humans, it is a potential drug target for treatment of primary hyperoxaluria, a genetic disorder where overproduction of oxalate results in the formation of kidney stones. In this study, steady-state and pre-steady-state kinetic approaches have been used to determine how pH affects the kinetic steps of the catalytic mechanism of human glycolate oxidase. The enzyme showed a Ping-Pong Bi-Bi kinetic mechanism between pH 6.0 and 10.0. Both the overall turnover of the enzyme (k(cat)) and the rate constant for anaerobic substrate reduction of the flavin were pH-independent at pH values above 7.0 and decreased slightly at lower pH, suggesting the involvement of an unprotonated group acting as a base in the chemical step of glycolate oxidation. The second-order rate constant for capture of glycolate (k(cat)/K(glycolate)) and the K(d)((app)) for the formation of the enzyme-substrate complex suggested the presence of a protonated group with apparent pK(a) of 8.5 participating in substrate binding. The k(cat)/K(oxygen) values were an order of magnitude faster when a group with pK(a) of 6.8 was unprotonated. These results are discussed in the context of the available three-dimensional structure of GOX.
Collapse
Affiliation(s)
| | - Giovanni Gadda
- From the Departments of Chemistry and
- Biologyand
- Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-4098
| |
Collapse
|
14
|
Abstract
Cholesterol oxidases are bifunctional flavoenzymes that catalyze the oxidation of steroid substrates which have a hydroxyl group at the 3beta position of the steroid ring system. The enzyme is found, in a wide range of bacterial species, in two forms: one with the FAD cofactor bound noncovalently to the enzyme; and one with the cofactor linked covalently to the protein. Here we discuss, compare and contrast the salient biochemical properties of the two forms of the enzyme. Specifically, the structural features are discussed that affect the redox potentials of the flavin cofactor, the chemical mechanism of substrate dehydrogenation by active-center amino acid residues, the kinetic parameters of both types of enzymes and the reactivity of reduced enzymes with molecular dioxygen. The presence of a molecular tunnel that is proposed to serve in the access of dioxygen to the active site and mechanisms of its control by a 'gate' formed by amino acid residues are highlighted.
Collapse
Affiliation(s)
- Alice Vrielink
- School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Crawley, Australia.
| | | |
Collapse
|
15
|
Tabacchi G, Zucchini D, Caprini G, Gamba A, Lederer F, Vanoni MA, Fois E. L-lactate dehydrogenation in flavocytochrome b2: a first principles molecular dynamics study. FEBS J 2009; 276:2368-80. [PMID: 19348008 DOI: 10.1111/j.1742-4658.2009.06969.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
First principles molecular dynamics studies on active-site models of flavocytochrome b2 (L-lactate : cytochrome c oxidoreductase, Fcb2), in complex with the substrate, were carried out for the first time to contribute towards establishing the mechanism of the enzyme-catalyzed L-lactate oxidation reaction, a still-debated issue. In the calculated enzyme-substrate model complex, the L-lactate alpha-OH hydrogen is hydrogen bonded to the active-site base H373 Nepsilon, whereas the Halpha is directed towards flavin N5, suggesting that the reaction is initiated by alpha-OH proton abstraction. Starting from this structure, simulation of L-lactate oxidation led to formation of the reduced enzyme-pyruvate complex by transfer of a hydride from lactate to flavin mononucleotide, without intermediates, but with alpha-OH proton abstraction preceding Halpha transfer and a calculated free energy barrier (12.1 kcal mol(-1)) consistent with that determined experimentally (13.5 kcal mol(-1)). Simulation results also revealed features that are of relevance to the understanding of catalysis in Fcb2 homologs and in a number of flavoenzymes. Namely, they highlighted the role of: (a) the flavin mononucleotide-ribityl chain 2'OH group in maintaining the conserved K349 in a geometry favoring flavin reduction; (b) an active site water molecule belonging to a S371-Wat-D282-H373 hydrogen-bonded chain, conserved in the structures of Fcb2 family members, which modulates the reactivity of the key catalytic histidine; and (c) the flavin C4a-C10a locus in facilitating proton transfer from the substrate to the active-site base, favoring the initial step of the lactate dehydrogenation reaction.
Collapse
Affiliation(s)
- Gloria Tabacchi
- Dipartimento di Scienze Chimiche ed Ambientali and INSTM, Università dell'Insubria, Como, Italy
| | | | | | | | | | | | | |
Collapse
|
16
|
Gadda G. Hydride transfer made easy in the reaction of alcohol oxidation catalyzed by flavin-dependent oxidases. Biochemistry 2009; 47:13745-53. [PMID: 19053234 DOI: 10.1021/bi801994c] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Choline oxidase (E.C. 1.1.3.17; choline-oxygen 1-oxidoreductase) catalyzes the two-step, four-electron oxidation of choline to glycine betaine with betaine aldehyde as enzyme-associated intermediate and molecular oxygen as final electron acceptor. Biochemical, structural, and mechanistic studies on the wild-type and a number of mutant forms of choline oxidase from Arthrobacter globiformis have recently been carried out, allowing for the delineation at molecular and atomic levels of the mechanism of alcohol oxidation catalyzed by the enzyme. First, the alcohol substrate is activated to its alkoxide species by the removal of the hydroxyl proton in the enzyme-substrate complex. The resulting activated alkoxide is correctly positioned for catalysis through electrostatic and hydrogen bonding interactions with a number of active site residues. After substrate activation and correct positioning are attained, alcohol oxidation occurs in a highly preorganized enzyme-substrate complex through quantum mechanical transfer of a hydride ion from the alpha-carbon of the chelated, alkoxide species to the N(5) atom of the enzyme-bound flavin. This mechanism in its essence is shared by another class of alcohol oxidizing enzymes that utilize a catalytic zinc to stabilize an alkoxide intermediate and NAD(P)(+) as the organic cofactor that accepts the hydride ion, whose paradigm example is alcohol dehydrogenase. It will be interesting to experimentally evaluate the attractive hypothesis of whether the mechanism of choline oxidase can be extended to other flavin-dependent enzymes as well as enzymes that utilize cofactors other than flavins in the oxidation of alcohols.
Collapse
Affiliation(s)
- Giovanni Gadda
- Departments of Chemistry and Biology, and The Center for Biotechnology and Drug Design, Georgia State University, Atlanta, Georgia 30302-4098, USA.
| |
Collapse
|