Dependent Formate Dehydrogenase Research Articles

Redox potentials elucidate the electron transfer pathway of NAD+-dependent formate dehydrogenases

Metal-dependent, nicotine adenine dinucleotide (NAD+)-dependent formate dehydrogenases (FDHs) are complex metalloenzymes coupling biochemical transformations through intricate electron transfer pathways. Rhodobacter capsulatus FDH is a model enzyme for understanding coupled catalysis, in that reversible CO2 reduction and formate oxidation are linked to a flavin mononuclotide (FMN)-bound diaphorase module via seven iron-sulfur (FeS) clusters as a dimer of heterotetramers. Catalysis occurs at a bis-metal-binding pterin (Mo) binding two molybdopterin guanine dinucleotides (bis-MGD), a protein-based Cys residue and a participatory sulfido ligand. Insights regarding the proposed electron transfer mechanism between the bis-MGD and the FMN have been complicated by the discovery that an alternative pathway might occur via intersubunit electron transfer between two [4Fe4S] clusters within electron transfer distance. To clarify this difference, the redox potentials of the bis-MGD and the FeS clusters were determined via redox titration by EPR spectroscopy. Redox potentials for the bis-MGD cofactor and five of the seven FeS clusters could be assigned. Furthermore, substitution of the active site residue Lys295 with Ala resulted in altered enzyme kinetics, primarily due to a more negative redox potential of the A1 [4Fe4S] cluster. Finally, characterization of the monomeric FdsGBAD heterotetramer exhibited slightly decreased formate oxidation activity and similar iron-sulfur clusters reduced relative to the dimeric heterotetramer. Comparison of the measured redox potentials relative to structurally defined FeS clusters support a mechanism by which electron transfer occurs within a heterotetrameric unit, with the interfacial [4Fe4S] cluster serving as a structural component toward the integrity of the heterodimeric structure to drive efficient catalysis.

A high catalytic efficiency and chemotolerant formate dehydrogenase from Bacillus simplex.

NAD+ -dependent formate dehydrogenase (FDH) catalyzes the conversion of formate and NAD+ to produce carbon dioxide and NADH. The reaction is biotechnologically important because FDH is widely used for NADH regeneration in various enzymatic syntheses. However, major drawbacks of this versatile enzyme in industrial applications are its low activity, requiring its utilization in large amounts to achieve optimal process conditions. Here, FDH from Bacillus simplex (BsFDH) was characterized for its biochemical and catalytic properties in comparison to FDH from Pseudomonas sp. 101 (PsFDH), a commonly used FDH in various biocatalytic reactions. The data revealed that BsFDH possesses high formate oxidizing activity with a kcat value of 15.3±1.9 s-1 at 25°C compared to 7.7±1.0 s-1 for PsFDH. At the optimum temperature (60°C), BsFDH exhibited 6-fold greater activity than PsFDH. The BsFDH displayed higher pH stability and a superior tolerance toward sodium azide and H2 O2 inactivation, showing a 200-fold higher Ki value for azide inhibition and remaining stable in the presence of 0.5% H2 O2 compared to PsFDH. The application of BsFDH as a cofactor regeneration system for the detoxification of 4-nitrophenol by the reaction of HadA, which produced a H2 O2 byproduct was demonstrated. The biocatalytic cascades using BsFDH demonstrated a distinct superior conversion activity because the system tolerated H2 O2 well. Altogether, the data showed that BsFDH is a robust enzyme suitable for future application in industrial biotechnology.

ENGINEERING THE N-TERMINAL SEQUENCE OF GLYCINE MAX SOYBEAN FORMATE DEHYDROGENASE

NAD(P)+ -dependent formate dehydrogenase (FDH, EC 1.2.1.2.) catalyzes the oxidation of formate ion with the coupled reduction of NAD(P)+ to NAD(P)H. Previously, in our laboratory, a genetic construct was obtained with the soyfdh2 gene encoding isoenzyme 2 of formate dehydrogenase from soybean Glycine max (SoyFDH). In this construct the nucleotide sequence encoding the signal peptide responsible for the transport of the pro-enzyme into the mitochondria of plant cells (the SoyFDH_L enzyme) was deleted. In this work, a second variant of SoyFDH_S was obtained, in which, compared to SoyFDH_L, the sequence at the N-terminus was reduced and changed to mimic the N-terminus sequence in FDH from Pseudomonas sp.101 bacteria. Next, a sequence of six histidine residues (His-tag) was added to the N-terminus of the long and short forms of SoyFDH. All four SoyFDH variants were expressed in E. coli BL21(DE3)CodonPlus, these enzymes were purified, their kinetic parameters were determined, and thermal stability was studied. In the case of SoyFDH_L, which is similar to the natural variant of the enzyme, both with and without His-tag, the expression level is two times higher compared to the truncated variant. The addition of His-tag to the N-terminus of enzymes reduces the level of expression. Changing the sequence of the N-terminus, as well as introducing the His-tag sequence to the N-terminus, does not significantly affect thermal stability of the enzymes at temperatures of 50–56 °C. However, due to the higher values of the activation enthalpy ΔH≠ of the thermal inactivation process, the shortened form at normal temperatures is 3 times more stable than the natural one. A comparison of the kinetic parameters of the two SoyFDH variants shows that the catalytic constants are the same, but the long version of SoyFDH_L has lower values KM HCOO– , and the short version has lower KM NAD+ values. The introduction of His-tag into the N-terminus of enzymes does not affect their kinetic parameters.

FORMATE DEHYDROGENASE: FROM NAD(P)H REGENERATION TO THE TARGET IN PATHOGENS BIOFILMS, A COMPONENT OF HIGHLY EFFICIENT HYBRID BIOCATALYSTS AND CO2 FIXATION FROM THE ATMOSPHERE

NAD(P)+ -dependent formate dehydrogenase (EC 1.2.1.2, FDH) catalyzes the simple from chemical and biological point of view reaction of formate ion oxidation to carbon dioxide with corresponding reduction of NAD(P)+ to NAD(P) H. Advances in the life sciences have shown that this reaction plays an extremely important role in a wide variety of organisms. The areas and types of practical applications of FDH are also permanently expanding. In this review we considered the main stages in the development of understanding and knowledge about the role of formate dehydrogenase in living systems. Achievements in creation of highly effi cient catalysts based on FDH for classic biotechnology as well as for new areas are also considered. The importance of appropriate choice of the initial FDH for the creation of a biocatalyst with the required and prescribed properties with minimal costs is shown. The prospects for the use of FDH for the fixation of CO2 are discussed.

Study of the structure-function relationship of formate dehydrogenase– an important enzyme for Staphylococcus aureus biofilms by rational design

NAD+-dependent formate dehydrogenase (FDH, EC 1.2.1.2) from the bacterium Staphylococcus aureus (SauFDH) plays an important role in the vital activity of this bacterium, especially in the form of biofilms. Understanding its mechanism and structure-function relationship can help to find special inhibitors of this enzyme, which can be used as medicines against staphylococci. The gene encoding SauFDH was successfully cloned and expressed in our laboratory. This enzyme has the highest kcat value among the described FDHs and also has a high temperature stability compared to other enzymes of this group. That is why it can also be considered as a promising catalyst for NAD(P)H regeneration in the processes of chiral synthesis with oxidoreductases. In this work, the principle of rational design was used to improve SauFDH catalytic efficiency. After bioinformatics analysis of the amino acid sequence in combination with visualization of the enzyme structure (PDB 6TTB), 9 probable catalytically significant positions 119, 194, 196, 217–219, 246, 303 and 323 were identified, and 16 new mutant forms of SauFDH were obtained and characterized by kinetic experiments. The introduction of the mentioned substitutions in most cases leads to a decrease in stability at high temperatures and an increase at low temperatures. Substitutions in positions 119 and 194 lead to a decreasing of KMNAD+. A consistent decrease in the Michaelis constant in the Ile-Val-Ala-Gly series at position 119 of SauFDH is shown. KMNAD+ of mutant SauFDH V119G decreased by 27 times compared to the wild-type enzyme. After substitution Phe194Val KMNAD + decreased by 3.5 times. The catalytic constant for this mutant form practically did not change. For this mutant form, an increase in catalytic efficiency was demonstrated through the use of a multicomponent buffer system.

Structural analysis of wild-type and Val120Thr mutant Candida boidinii formate dehydrogenase by X-ray crystallography.

Candida boidinii NAD+-dependent formate dehydrogenase (CbFDH) has gained significant attention for its potential application in the production of biofuels and various industrial chemicals from inorganic carbon dioxide. The present study reports the atomic X-ray crystal structures of wild-type CbFDH at cryogenic and ambient temperatures, as well as that of the Val120Thr mutant at cryogenic temperature, determined at the Turkish Light Source `Turkish DeLight'. The structures reveal new hydrogen bonds between Thr120 and water molecules in the active site of the mutant CbFDH, suggesting increased stability of the active site and more efficient electron transfer during the reaction. Further experimental data is needed to test these hypotheses. Collectively, these findings provide invaluable insights into future protein-engineering efforts that could potentially enhance the efficiency and effectiveness of CbFDH.

NAD+-Dependent Formate Dehydrogenase from Themotolerant Yeast Ogataea parapolymorpha: Properties and Protein Engineering of the N-Terminal Sequence.

Previously, the gene of formate dehydrogenase (FDH, EC 1.2.1.2) from the thermotolerant methylotrophic yeast Ogataea parapolymorpha DL 1 (OpaFDH) was cloned in our laboratory. Recombinant enzyme with additional glycine amino acid residue (OpaFDH_GK) was obtained in Escherichia coli cells in active and soluble form with a yield of more than 1 g per liter of the medium. In the present work, a detailed comparison of this enzyme with FDHs from other sources was carried out. Among eukaryotic formate dehydrogenases, OpaFDH has the highest thermal stability. To elucidate effect of N-terminal residue on the properties of the enzyme, OpaFDH_K (identical to natural) and OpaFDH_AK variants containing an additional Ala residue at the N-terminus were also obtained. It was shown that addition of an Ala residue to the N-terminus reduces four-fold the rate constant of thermal inactivation compared with the addition of a Gly residue. Addition of six more histidine residues to the N-terminus of OpaFDH_AK leads to acceleration of purification, practically does not affect kinetic parameters, but somewhat reduces thermal stability, which, however, can be restored to the level of OpaFDH_AK stability by adding 0.5 M NaCl.

Chimeric versus isolated proteins: Biochemical characterization of the NADP+-dependent formate dehydrogenase from Pseudomonas sp. 101 fused with the Baeyer-Villiger monooxygenase from Thermobifida fusca

The expression of multifunctional proteins can facilitate the setup of a biotechnology process that requires multiple functions absolved by different proteins. Herein the functional and conformational characterization of a formate dehydrogenase-monooxygenase chimera enzyme is presented. The fused enzyme (FDH-PAMO) was prepared by linking the C-terminus of the mutant NADP+-dependent formate dehydrogenase from Pseudomonas sp. 101 (FDH) to the N-terminus of the NADPH-dependent monooxygenase from Thermobifida fusca (PAMO) through a peptide linker of 9 amino acids (ASGGGGSGT) generating a chimera protein of 107,056 Da. The catalytic properties (e.g., kinetic parameters kcat and Km), stability, fluorescence and circular dichroism spectra showed that the so-obtained chimera enzyme FDH-PAMO retains the same functional and conformational properties of the two parental enzymes. Furthermore, SEC chromatographic analysis indicated that, in solution (pH 7.4), FDH-PAMO assembles to tetramers (up to 4.2 %) due to the propensity of FDH and PAMO to form dimers, up to 96.6 % and 6.2 %, respectively. This study provides valuable insights into the structural stability of a thermostable protein (e.g., PAMO) after increasing its size through fusion with another similarly sized thermostable protein (e.g., FDH).

ENGINEERING THE ACTIVE SITE OF FORMATE DEHYDROGE-NASE FROM STAPHYLOCOCCUS AUREUS: INTRODUCTION TO THE STRUCTURE OF THE ADDITIONAL LOOP AND HISTIDINE RESIDUES

NAD+-dependent formate dehydrogenase (EC 1.2.1.2, FDH) from pathogenic bacterium Staphylococcus aureus (SauFDH) differs signi cantly from other FDHs both in terms of primary structure and catalytic properties. A distinctive feature of SauFDH is the highest (about 2.5-3 times) speci c activity compared to other formate dehydrogenases. At the same time, SauFDH has high Michaelis constants for both substrates. Based on the analysis of threedimensional structures and the alignment of amino acid sequences, substitutions promising in terms of changing catalytic parameters were selected. The replacement of I220H resulted in an increase in KMNAD+; the value of kcat has not changed. When Т250Н is replaced, an increase in KMNAD+ is observed, kcat decreases from 20 to 13 s-1. The replacement of K368H led to a slight increase in KMNAD+, kcat decreased from 20 s-1 to 6 s-1. The introduction of TGA and AGA additional inserts in α-helix at the C-terminus of the enzyme led to an increase in KMNAD+ and KMHCOO-. A bigger effect was observed for KMNAD+ - the difference was more than 10 times. For mutant SauFDH with insertions kcat signi cantly reduced to 4 s-1. Similar results were observed for mutants with multipoint substitutions. Thus, the C-terminal sequence has been shown to play an important role in the catalysis of SauFDH.

HIGHLY STABLE MUTANT BACTERIAL FORMAT DEHYDROGENASE WITH IMPROVED CATALYTIC PROPERTIES

NAD+-dependent formate dehydrogenase (FDH, EC 1.2.1.2) from methylotrophic bacterium Pseudomonas sp.101 (PseFDH) has one of the highest thermal stability among all known enzymes of this group. The introduction of a number of amino acid substitutions into PseFDH made it possible to obtain a multipoint mutant PseFDH SM4S enzyme with even higher temperature and chemical stability. Previously, we showed that the introduction of additional single point replacements S131A, or S160A, or E170D into PseFDH SM4S led to further stabilization of the enzyme. In this work, based on the PseFDH SM4S S131A mutant, new mutant FDHs obtained, in which, compared to PseFDH SM4S, we added double S131A/E170D (M2), triple S131A/S160A/E170D (M3) and quadruple S131A/S160A/ E170D/S145A (PseFDH SM4A M3) amino acids replacements. The new PseFDH mutants were overexpressed in E. coli cells, puri ed and characterized. The S131A/E170D and S131A/S160A/E170D changes provided further improving thermal stability. The introduction of the S145A substitution into PseFDH SM4S M4 leads to a signi cant decrease in KMNAD+ and KMHCOO- while maintaining the catalytic constant at the same level. This mutant form can be successfully used in NADH regeneration systems, as well as for the detection of NAD+ and formate in biological systems.

Genes of NAD+-Dependent Formate Dehydrogenases in Taxonomy of Aerobic Methylotrophic Bacteria of the Genus Ancylobacter

Genes of NAD+-Dependent Formate Dehydrogenases in Taxonomy of Aerobic Methylotrophic Bacteria of the Genus Ancylobacter

Effect of the Components of a Buffer Solution on the Catalytic Activity of the NAD+-Dependent Formate Dehydrogenase from the Bacterium Staphylococcus aureus

Effect of the Components of a Buffer Solution on the Catalytic Activity of the NAD+-Dependent Formate Dehydrogenase from the Bacterium Staphylococcus aureus

Enhanced thermostability of formate dehydrogenase via semi-rational design

An NAD+-dependent formate dehydrogenase from Lodderomyces elongisporus (LeFDH) was expressed in Escherichia coli and then purified by nickel affinity chromatography. The analysis of enzymatic properties showed that the specific activity of LeFDH was much high (16.26 U·mg–1), while the thermal stability may be insufficient for industrial application. To further enhance the thermal stability by semi-rational design, sequences alignment, homologous modeling and molecular dynamic simulations were conducted. As a result, seven non-conserved amino acid residues far from the active center were selected for site-directed mutagenesis. Several mutants as well as a binary mutant displayed improved thermal stability and unreduced specific activity. Then temperature and pH stability, kinetic parameters and specific activity, and structural characteristics of wild-type and mutant LeFDH were compared and evaluated. The variant K21P/K22R exhibited an increased half-life by 211% at 60 °C and a 4.5 °C higher Tm than those of wild type, and good stability in alkaline environment. This binary mutant enhances the operational stability of LeFDH in the catalytic reaction and thus improves its potential for application in coenzyme regenerations.

Metal cofactor structure in a tungsten dependent formate dehydrogenase: Determination through EPR spectroscopy, isotopic enrichment and DFT calculations

Metal cofactor structure in a tungsten dependent formate dehydrogenase: Determination through EPR spectroscopy, isotopic enrichment and DFT calculations

Engineering nonphotosynthetic carbon fixation for production of bioplastics by methanogenic archaea

The conversion of CO2 to value-added products allows both capture and recycling of greenhouse gas emissions. While plants and other photosynthetic organisms play a key role in closing the global carbon cycle, their dependence on light to drive carbon fixation can be limiting for industrial chemical synthesis. Methanogenic archaea provide an alternative platform as an autotrophic microbial species capable of non-photosynthetic CO2 fixation, providing a potential route to engineered microbial fermentation to synthesize chemicals from CO2 without the need for light irradiation. One major challenge in this goal is to connect upstream carbon-fixation pathways with downstream biosynthetic pathways, given the distinct differences in metabolism between archaea and typical heterotrophs. We engineered the model methanogen, Methanococcus maripaludis, to divert acetyl-coenzyme A toward biosynthesis of value-added chemicals, including the bioplastic polyhydroxybutyrate (PHB). A number of studies implicated limitations in the redox pool, with NAD(P)(H) pools in M. maripaludis measured to be <15% of that of Escherichia coli, likely since methanogenic archaea utilize F420 and ferredoxins instead. Multiple engineering strategies were used to precisely target and increase the cofactor pool, including heterologous expression of a synthetic nicotinamide salvage pathway as well as an NAD+-dependent formate dehydrogenase from Candida boidinii. Engineered strains of M. maripaludis with improved NADH pools produced up to 171 ± 4 mg/L PHB and 24.0 ± 1.9% of dry cell weight. The metabolic engineering strategies presented in this study broaden the utility of M. maripaludis for sustainable chemical synthesis using CO2 and may be transferable to related archaeal species.

The role of Tyr102 residue in the functioning of bacterial NAD+-dependent formate dehydrogenase of Pseudomonas sp. 101

Once you have missed the first button …, you'll never manage to button upJohann Wolfgang von GoetheFormate oxidation is a final step of methanol oxidation in methylotrophic prokaryotes and is important for detoxification of formate in other organisms. The structural mechanism of the formate dehydrogenase (FDH) of Pseudomonas sp. 101 has been studied for about 30 years. In the active center of FDH, the oxidation of formic acid into carbon dioxide in a NAD+-dependent way takes place. Residues that form the active center of that enzyme, as well as those that form the so-called substrate channel, are engaged in the catalytic cycle. Our study allowed to characterize a new residue, Tyr102, involved in the work of the enzyme. This residue is located in the outer neck of the substrate channel (at the beginning of the path of the substrate to the active center) and acts as a “button” which connects two enzyme domains into an active, “buttoned up” conformation. Our study of the kinetic parameters of mutant enzymes has shown that Tyr102Phe substitution leads to an approximately 80-fold increase of the Michaelis constant relative to the native enzyme, unlike Phe311Trp and Phe311Tyr substitution of neighboring residue Phe311. Our analysis of the Tyr102Phe mutant in the open conformation by X-ray crystallography has shown that its overall fold remains almost the same as that of the native enzyme. Molecular dynamics simulations of the ternary complexes of the native FDH enzyme and its Tyr102Phe mutant showed that Tyr102Phe substitution results in the loss of an interdomain hydrogen bond between the Tyr102 and Gln313 residues, which, in turn, destabilizes the closed conformation and affects the isolation of the FDH active site from water molecules. Our structural investigations have shown that Tyr102Phe replacement also leads to the destruction of interdomain contacts of Phe102 with Phe311, Pro312 residues, and decreases the stability of the Leu103-Val127 beta bridge. Phylogenetic analysis also confirmed the importance of the Tyr102 residue for enzymes from the FDH family, in which it is absolutely conserved.

Crystallographic analyses of the FdsBG subcomplex of the cytosolic formate dehydrogenase FdsDABG from Cupriavidus necator

The soluble molybdenum-containing, NAD+-dependent formate dehydrogenase FdsDABG from Cupriavidus necator belongs to the NADH dehydrogenase superfamily and catalyzes the oxidation of formate to CO2 and the reduction of NAD+ to NADH. Here, we present the first description of the crystal structure of the FdsBG subcomplex with and without bound NADH. Compared to other NADH dehydrogenases, FMN is closer to both iron-sulfur clusters, Fe4S4 in FdsB and Fe2S2 in FdsG. Based on the NADH-bound structure, we conclude that the nicotinamide ring of NADH can only access the re-face of FMN. However, the binding of NADH reduces the affinity of the isoalloxazine ring of FMN and allows for a conformational change of the residues that are known to undergo an oxidation state-dependent peptide flip in canonical NADH dehydrogenases.

Effect of Met/Leu substitutions on the stability of NAD+-dependent formate dehydrogenases from Gossypium hirsutum.

NAD+-dependent formate dehydrogenases (FDHs) are extensively used in the regeneration of NAD(P)H and the reduction of CO2 to formate. In addition to their industrial importance, FDHs also play a crucial role in the maintenance of a reducing environment to combat oxidative stress in plants. Therefore, it is important to investigate the response of NAD+-dependent FDH against both temperature and H2O2, to understand the defense mechanisms, and to increase its stability under oxidative stress conditions. In the present study, we characterized the oxidative and thermal stability of NAD+-dependent FDH isolated from cotton, Gossypium hirsutum (GhFDH), by investigating the effect of Met/Leu substitutions in the positions of 225, 234, and 243. Results showed that the single mutant, M234L (0.72 s-1 mM-1), and the triple mutant, M225L/M234L/M243L (0.55 s-1 mM-1), have higher catalytic efficiency than the native enzyme. Substitution of methionine by leucine on the position of 243 increased the free energy gain by 670 J mol-1. The most remarkable results in chemical stability were seen for double and triple mutants, cumulatively. Double and triple substitution of Met to Leu (M225L/M243L and M225L/M243L/M234L) reduce the kefin by a factor of 2 (12.3×10-5 and 12.8×10-5 s-1, respectively.Key points• The closer the residue to NAD+, in which we substituted methionine to leucine, the lower the stability against H2O2 we observed.• The significant gain in the Tm value for the M243L mutant was observed as +5°C.• Residue 234 occupies a critical position for oxidation defense mechanisms. Graphical abstract (a) Methionine amino acids on the protein surface are susceptible to oxidative stress and can be converted to methionine sulfoxide by reactive oxygen derivatives (such as hydrogen peroxide). Therefore, they are critical regions in the change of protein conformation and loss of activity. (b) Replacing the amino acid methionine, which is susceptible to oxidation due to the sulfur group, with the oxidation-resistant leucine amino acid is an important strategy in increasing oxidative stability.

The dyad of the Y-junction- and a flavin module unites diverse redox enzymes

The concomitant presence of two distinctive polypeptide modules, which we have chosen to denominate as the “Y-junction” and the “flavin” module, is observed in 3D structures of enzymes as functionally diverse as complex I, NAD(P)-dependent [NiFe]-hydrogenases and NAD(P)-dependent formate dehydrogenases. Amino acid sequence conservation furthermore suggests that both modules are also part of NAD(P)-dependent [FeFe]-hydrogenases for which no 3D structure model is available yet. The flavin module harbours the site of interaction with the substrate NAD(P) which exchanges two electrons with a strictly conserved flavin moiety. The Y-junction module typically contains four iron-sulphur centres arranged to form a Y-shaped electron transfer conduit and mediates electron transfer between the flavin module and the catalytic units of the respective enzymes. The Y-junction module represents an electron transfer hub with three potential electron entry/exit sites. The pattern of specific redox centres present both in the Y-junction and the flavin module is correlated to present knowledge of these enzymes' functional properties. We have searched publicly accessible genomes for gene clusters containing both the Y-junction and the flavin module to assemble a comprehensive picture of the diversity of enzymes harbouring this dyad of modules and to reconstruct their phylogenetic relationships. These analyses indicate the presence of the dyad already in the last universal common ancestor and the emergence of complex I's EFG-module out of a subgroup of NAD(P)- dependent formate dehydrogenases.

Preparation of Recombinant Formate Dehydrogenase from Thermotolerant Yeast Ogataea parapolymorpha and Crystallization of Its Apo- and Holo- Forms

NAD+-dependent formate dehydrogenase from thermotolerant yeast Ogataea parapolymorpha DL-1 (OpaFDH, EC 1.2.1.2) with the additional N-terminal Gly residue and its double mutant OpaFDH_AD were overexpressed in E. coli cells. The enzyme yield was, respectively, 6000 and 6200 units per liter of the cultivation medium. Purified enzymes were obtained as homogeneous preparations with a yield of 62%. The purification procedure included ultrasonic cell disruption, heat treatment of cell free extracts at 55°C for 15 min, and hydrophobic chromatography on the Phenyl Sepharose Fast Flow. Crystallization experiments with wild-type OpaFDH resulted in the preparation of crystals of the apo-form but not the holo-form. Crystals of the holo-form were prepared in the case of the OpaFDH_AD mutant in the presence of 7 mM NAD+ and 10 mM sodium azide. The size and quality of the crystals are sufficient to collect X-ray diffraction data and determine the enzyme three-dimensional structure.