GO:0140170 D-lactate dehydrogenase (FAD) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0140170 defines the molecular function that catalyzes the reaction (R)-lactate + FAD + H+ = FADH2 + pyruvate.
• FAD-dependent D-lactate dehydrogenases are found in bacteria, archaea, and some eukaryotes, and they use FAD as a tightly or loosely bound cofactor.
• Some family members require additional cofactors such as Zn2+ or Fe-S clusters and can donate electrons to quinone or artificial dyes.
• Human D-lactate dehydrogenase (LDHD) is a mitochondrial flavoenzyme whose dysfunction is linked to D-lactate acidosis and oxalate sensitivity.
• These enzymes are studied for their roles in microbial metabolism, gut microbiome function, and potential biotechnological applications.
• CRISPR-based knockout, point mutation, knock-in, and overexpression models enable precise dissection of D-lactate dehydrogenase (FAD) activity in health and disease.
Description
D-lactate dehydrogenase (FAD) activity, encoded by the Gene Ontology term GO:0140170, is a molecular function that catalyzes the oxidation of (R)-lactate (D-lactate) to pyruvate using flavin adenine dinucleotide (FAD) as an electron acceptor. This activity is distinct from NAD-dependent lactate dehydrogenases and is found across diverse organisms, from anaerobic bacteria and archaea to humans. The enzyme typically couples D-lactate oxidation to the reduction of FAD to FADH2, which can subsequently transfer electrons to quinones or artificial electron acceptors. Understanding this activity is important for researchers studying microbial energy metabolism, gut microbiome interactions, and human metabolic disorders such as D-lactate acidosis. The unique cofactor requirements and substrate specificity of FAD-dependent D-lactate dehydrogenases make them attractive targets for biochemical characterization and therapeutic development.
D-lactate dehydrogenase (FAD) activity At A Glance
| GO ID | GO:0140170 |
|---|---|
| GO term | D-lactate dehydrogenase (FAD) activity |
| Ontology | molecular_function |
| Synonym | (none) |
| Major function | Catalysis of (R)-lactate + FAD + H+ = FADH2 + pyruvate |
| Cofactor | FAD (flavin adenine dinucleotide) |
| Substrate | (R)-lactate (D-lactate) |
| Product | Pyruvate and FADH2 |
| Representative enzymes | D-lactate dehydrogenases from Desulfovibrio vulgaris, Sulfolobus tokodaii, Archaeoglobus fulgidus, Megasphaera elsdenii, and human LDHD |
What Is GO:0140170?
GO:0140170 describes the catalysis of the reaction: (R)-lactate + FAD + H+ = FADH2 + pyruvate. In other words, it is the FAD-dependent oxidation of D-lactate to pyruvate, where FAD serves as the primary electron acceptor. This activity is classified as a molecular_function in the Gene Ontology and is distinct from NAD-dependent or quinone-dependent D-lactate dehydrogenases.
Why Is D-lactate dehydrogenase (FAD) activity Important in Cell Biology?
D-lactate dehydrogenase (FAD) activity is critical for understanding microbial and human metabolic pathways that handle D-lactate, a metabolite that can accumulate to toxic levels in certain conditions. In bacteria and archaea, these enzymes participate in anaerobic respiration and energy conservation, often linking D-lactate oxidation to quinone reduction. In humans, the mitochondrial enzyme LDHD is the primary D-lactate dehydrogenase, and mutations in LDHD cause D-lactate acidosis, a rare but serious metabolic disorder. Moreover, D-lactate is a key metabolite in gut microbiome-host interactions, and FAD-dependent D-lactate dehydrogenases from gut bacteria influence host physiology. Studying this activity also has biotechnological relevance, as these enzymes can be used in biosensors or biocatalysis.
• Provides a route for D-lactate utilization in anaerobic bacteria and archaea.
• Links microbial metabolism to host health via gut microbiome D-lactate production.
• Human LDHD dysfunction causes D-lactate acidosis, a metabolic disease.
• Enzymes with this activity are potential targets for antimicrobials.
• FAD-dependent D-lactate dehydrogenases are used in industrial biocatalysis and biosensing.
• They contribute to electron transfer chains by reducing quinones.
• They are models for studying flavin chemistry and protein-cofactor interactions.
• They help maintain redox balance in anaerobic environments.
• They are relevant to understanding oxalate metabolism and kidney stone disease.
• They enable metabolic engineering of D-lactate pathways in microbes.
What Happens During D-lactate dehydrogenase (FAD) activity?
Substrate Binding and Orientation
In simple terms: The enzyme grabs D-lactate and holds it in the right position for a chemical reaction.
The first step in D-lactate dehydrogenase (FAD) activity is the binding of the substrate (R)-lactate to the enzyme's active site. Structural and biochemical studies of enzymes such as the D-lactate dehydrogenase from Desulfovibrio vulgaris and Sulfolobus tokodaii have shown that the substrate is positioned near the FAD cofactor to facilitate hydride transfer. The enzyme typically forms a ternary complex with D-lactate and FAD, and the binding is often accompanied by conformational changes that optimize catalysis.
Hydride Transfer and FAD Reduction
In simple terms: The enzyme removes two electrons from D-lactate and gives them to FAD, turning it into FADH2.
Once bound, the enzyme catalyzes the transfer of a hydride ion from the alpha-carbon of D-lactate to the isoalloxazine ring of FAD, resulting in the reduction of FAD to FADH2 and the formation of pyruvate. This step is the core of the catalytic mechanism and is common to all FAD-dependent D-lactate dehydrogenases. The reaction is stereospecific for the D-isomer of lactate, distinguishing it from L-lactate dehydrogenases.
Electron Transfer to Acceptors
In simple terms: The reduced FADH2 passes its electrons to other molecules, such as quinones or artificial dyes.
After FAD is reduced to FADH2, the electrons are transferred to a terminal electron acceptor. In many bacterial and archaeal systems, the physiological acceptor is a quinone, as shown for a multidomain NAD-independent D-lactate dehydrogenase that utilizes FAD and Fe-S clusters to reduce quinone. In vitro, artificial electron acceptors such as dichlorophenolindophenol (DCPIP) or ferricyanide are often used to measure activity. The ability to transfer electrons to various acceptors reflects the enzyme's role in respiratory chains.
Product Release and Enzyme Turnover
In simple terms: The enzyme releases pyruvate and reoxidizes FAD to start another round.
Following electron transfer, pyruvate is released from the active site, and the enzyme returns to its oxidized state, ready for another catalytic cycle. For enzymes with loosely bound FAD, such as the archaeal D-lactate dehydrogenase from Sulfolobus tokodaii, the cofactor may dissociate and reassociate during turnover. The overall rate of catalysis is influenced by the binding affinity for FAD and the efficiency of electron transfer to acceptors.
Key Genes Involved in GO:0140170 D-lactate dehydrogenase (FAD) activity
The following genes and proteins are representative of D-lactate dehydrogenase (FAD) activity across different organisms.
| Gene | Major Role | Research Relevance |
|---|---|---|
| LDHD (human) | Mitochondrial D-lactate dehydrogenase | Mutations cause D-lactate acidosis; target for metabolic studies |
| dld (Desulfovibrio vulgaris) | D-lactate dehydrogenase | Model for anaerobic sulfate-reducing bacteria |
| STK_16540 (Sulfolobus tokodaii) | FAD-dependent D-lactate dehydrogenase | Thermostable enzyme for biocatalysis |
| AF_0808 (Archaeoglobus fulgidus) | Zn2+-dependent FAD D-lactate dehydrogenase | Example of metalloflavoprotein |
| dld (Megasphaera elsdenii) | FAD-dependent D-lactate dehydrogenase | Well-characterized flavoenzyme |
| lldD (Escherichia coli) | NAD-independent D-lactate dehydrogenase | Model for respiratory chain |
| D-LDH (isopod gut metagenome) | Novel FAD-dependent D-lactate dehydrogenase | Biotechnological potential |
| LDHD (mouse) | D-lactate dehydrogenase | Animal model for D-lactate metabolism |
| dld (Clostridium) | D-lactate dehydrogenase | Fermentation pathways |
| dld (Lactobacillus) | D-lactate dehydrogenase | Probiotic and food industry relevance |
| dld (Bifidobacterium) | D-lactate dehydrogenase | Gut microbiome interactions |
| dld (Thermus) | Thermostable D-lactate dehydrogenase | Industrial biocatalysis |
| dld (Pyrococcus) | Hyperthermophilic D-lactate dehydrogenase | Enzyme evolution studies |
| dld (Methanocaldococcus) | Archaeal D-lactate dehydrogenase | Methanogenesis and redox balance |
| dld (Shewanella) | D-lactate dehydrogenase | Electron transfer to electrodes |
| dld (Pseudomonas) | D-lactate dehydrogenase | Biodegradation and metabolism |
| dld (Bacillus) | D-lactate dehydrogenase | Spore formation and metabolism |
How Is D-lactate dehydrogenase (FAD) activity Regulated?
The activity of D-lactate dehydrogenase (FAD) is regulated at multiple levels. In bacteria and archaea, expression of the encoding genes is often induced by the presence of D-lactate or anaerobic conditions. For example, the multidomain D-lactate dehydrogenase in Escherichia coli is part of the respiratory chain and its expression is controlled by oxygen availability and carbon source. In humans, LDHD is a mitochondrial enzyme whose activity can be inhibited by oxalate, and mutations in LDHD impair its catalytic function, leading to D-lactate accumulation. Additionally, the binding of FAD to the enzyme can be loose or tight, affecting activity; some archaeal enzymes show loose FAD binding that may be regulated by cofactor availability. Post-translational modifications and protein-protein interactions may also modulate activity, though specific mechanisms remain to be fully elucidated.
D-lactate dehydrogenase (FAD) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| LDHD (human) | D-lactate acidosis | Knockout HEK293 cells; patient-derived fibroblasts |
| LDHD (human) | Oxalate sensitivity | Point mutation knock-in in HeLa cells |
| Gut microbial dld | D-lactate accumulation in short bowel syndrome | Gnotobiotic mouse models |
| LDHD (mouse) | Metabolic acidosis | Ldhd knockout mice |
| dld (E. coli) | Respiratory chain function | Deletion mutants in E. coli |
D-Lactate Acidosis
D-lactate acidosis is a rare metabolic disorder characterized by elevated levels of D-lactate in the blood, leading to neurological symptoms and metabolic acidosis. Mutations in the human LDHD gene, which encodes the mitochondrial D-lactate dehydrogenase, severely impair its catalytic activity, resulting in reduced D-lactate clearance. Studies have shown that these mutations, such as those identified in patients, lead to decreased enzyme stability and activity, and oxalate further inhibits the enzyme, exacerbating the condition. This highlights the critical role of FAD-dependent D-lactate dehydrogenase in human D-lactate metabolism.
Gut Microbiome and Metabolic Disorders
D-lactate produced by gut bacteria can enter the bloodstream and contribute to D-lactate acidosis, especially in patients with short bowel syndrome or compromised intestinal barriers. FAD-dependent D-lactate dehydrogenases from gut bacteria, such as those identified in isopod gut metagenomes, are involved in D-lactate production and utilization. Understanding these microbial enzymes may provide insights into probiotic interventions and the management of D-lactate-related conditions.
Kidney Stone Disease and Oxalate Metabolism
Oxalate is a known inhibitor of human D-lactate dehydrogenase, and elevated oxalate levels are associated with kidney stone formation. The inhibition of LDHD by oxalate suggests a link between D-lactate metabolism and oxalate homeostasis. Further research into FAD-dependent D-lactate dehydrogenases may uncover therapeutic strategies for hyperoxaluria and related disorders.
From D-lactate dehydrogenase (FAD) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of LDHD cause D-lactate accumulation? | LDHD knockout cell line (e.g., HEK293) |
| How do patient mutations affect LDHD activity? | Point mutation knock-in (e.g., LDHD R370C) |
| Can we tag LDHD to study localization? | Knock-in of FLAG or GFP tag at endogenous locus |
| What is the effect of LDHD overexpression? | Overexpression of LDHD in mammalian cells |
| How does microbial D-lactate dehydrogenase contribute to gut metabolism? | Knockout of dld in gut bacteria |
| Can we screen for inhibitors of LDHD? | CRISPR library screening or small molecule screens |
How to Study the D-lactate dehydrogenase (FAD) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| DCPIP reduction assay | Enzyme activity | Kinetic characterization of D-lactate dehydrogenases |
| X-ray crystallography | Three-dimensional structure | Active site and cofactor binding studies |
| CRISPR knockout | Loss of gene function | Phenotypic analysis of LDHD in cells |
| Site-directed mutagenesis | Effect of specific mutations | Modeling patient variants |
| Metabolomics (LC-MS) | D-lactate and pyruvate levels | In vivo pathway flux |
| Western blot | Protein expression | Validation of knockout or overexpression |
| Fluorescence microscopy | Subcellular localization | Tagged LDHD imaging |
| RNA-seq | Transcriptional changes | Global response to LDHD manipulation |
Enzymatic Activity Assays
The most direct method to study D-lactate dehydrogenase (FAD) activity is to measure the reduction of FAD or artificial electron acceptors such as DCPIP or ferricyanide spectrophotometrically. These assays use D-lactate as substrate and monitor the change in absorbance at specific wavelengths. Such assays are used to characterize enzyme kinetics, substrate specificity, and inhibitor sensitivity, as demonstrated for the human LDHD and bacterial enzymes.
Structural Biology
X-ray crystallography and cryo-electron microscopy can provide atomic-level insights into the active site, cofactor binding, and conformational changes of D-lactate dehydrogenases. Structures of enzymes from Desulfovibrio vulgaris and Sulfolobus tokodaii have revealed key residues involved in substrate binding and catalysis. These methods help in understanding how mutations affect enzyme function.
Genetic and CRISPR Approaches
CRISPR-Cas9 genome editing enables the creation of knockout, point mutation, and knock-in cell models to study the physiological roles of D-lactate dehydrogenase (FAD) activity. For example, knockout of LDHD in human cells can reveal its contribution to D-lactate clearance, while point mutations can mimic patient variants. Overexpression models can help assess gain-of-function effects.
Metabolomics and Flux Analysis
Mass spectrometry-based metabolomics can quantify D-lactate and pyruvate levels in cells and tissues, providing a readout of D-lactate dehydrogenase activity in vivo. Isotope tracing can further elucidate metabolic fluxes through this pathway. These methods are essential for linking enzyme activity to disease phenotypes.
How CRISPR Can Be Used to Study GO:0140170 D-lactate dehydrogenase (FAD) activity
Knockout
CRISPR-Cas9 knockout of LDHD or microbial dld genes can completely abolish D-lactate dehydrogenase (FAD) activity, allowing researchers to study its role in D-lactate metabolism and related phenotypes. For example, LDHD knockout cells accumulate D-lactate and can be used to model D-lactate acidosis. Knockout of bacterial dld genes can reveal their contribution to anaerobic respiration.
Point Mutation
Introducing specific point mutations via CRISPR homology-directed repair can mimic naturally occurring patient variants, such as those in LDHD associated with D-lactate acidosis. These models help determine how single amino acid changes affect enzyme activity, stability, and substrate binding. Point mutation knock-in is also useful for studying catalytic residues identified in structural studies.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) or fluorescent proteins (e.g., GFP) at the endogenous LDHD locus enables real-time tracking of protein localization and interaction without overexpression artifacts. This approach is valuable for studying mitochondrial targeting and dynamics of LDHD. Knock-in of reporter genes can also be used for high-throughput screening.
Overexpression
Overexpression of wild-type or mutant LDHD in mammalian cells can enhance D-lactate clearance and protect against D-lactate toxicity. Overexpression models are useful for gain-of-function studies and for testing the effects of pharmacological inhibitors. In microbial systems, overexpression of dld genes can increase D-lactate utilization for biotechnological applications.
How EDITGENE Supports D-lactate dehydrogenase (FAD) activity Research
Researchers studying D-lactate dehydrogenase (FAD) activity-related genes often need to determine whether a candidate gene is causally involved in metabolic pathways, disease phenotypes, or microbial physiology. Precise genetic models are essential to move from correlation to causation.
Contact EDITGENE today to design your custom CRISPR model for D-lactate dehydrogenase (FAD) activity research.
Frequently Asked Questions About D-lactate dehydrogenase (FAD) activity
What is D-lactate dehydrogenase (FAD) activity?
It is a molecular function defined by GO:0140170 that catalyzes the reaction (R)-lactate + FAD + H+ = FADH2 + pyruvate, using FAD as an electron acceptor.
What genes are involved in D-lactate dehydrogenase (FAD) activity?
Key genes include human LDHD, bacterial dld from Desulfovibrio vulgaris, Sulfolobus tokodaii, Archaeoglobus fulgidus, Megasphaera elsdenii, and Escherichia coli lldD.
What is the difference between D-lactate dehydrogenase (FAD) and NAD-dependent D-lactate dehydrogenase?
FAD-dependent enzymes use FAD as a cofactor and often transfer electrons to quinones, while NAD-dependent enzymes use NAD+ as an electron acceptor.
Which diseases are associated with D-lactate dehydrogenase (FAD) activity?
Mutations in human LDHD cause D-lactate acidosis, and the enzyme is inhibited by oxalate, linking it to kidney stone disease.
How can I study D-lactate dehydrogenase (FAD) activity in the lab?
Common methods include enzymatic assays with DCPIP, CRISPR knockout/knock-in models, metabolomics, and structural biology.
What cofactors are required for D-lactate dehydrogenase (FAD) activity?
FAD is the primary cofactor, but some enzymes also require Zn2+ or Fe-S clusters.
Is D-lactate dehydrogenase (FAD) activity found in humans?
Yes, the human LDHD gene encodes a mitochondrial FAD-dependent D-lactate dehydrogenase.
What are the substrates and products of D-lactate dehydrogenase (FAD) activity?
The substrate is (R)-lactate (D-lactate) and the products are pyruvate and FADH2.
How is D-lactate dehydrogenase (FAD) activity regulated?
Regulation occurs at transcriptional and post-translational levels, and FAD binding affinity can modulate activity.
Can CRISPR be used to study D-lactate dehydrogenase (FAD) activity?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are powerful tools to dissect the function of LDHD and related genes.
Conclusion
D-lactate dehydrogenase (FAD) activity (GO:0140170) is a fundamental enzymatic function that bridges microbial and human metabolism. Its ability to oxidize D-lactate using FAD as a cofactor is critical for energy production in anaerobic organisms and for D-lactate clearance in humans. Dysregulation of this activity, particularly through mutations in human LDHD, leads to D-lactate acidosis and related metabolic complications. Continued research using advanced CRISPR models and biochemical assays will further illuminate its roles and therapeutic potential.
References
- 1. Coelho C et al.. 2025. Shotgun metagenomic mining reveals a new FAD-dependent D-lactate dehydrogenase in an isopod gut microbiome.. Appl Environ Microbiol 91(12):e0148025 PMID: 41231970
- 2. Ogata M et al.. 1981. D-lactate dehydrogenase of Desulfovibrio vulgaris.. J Biochem 89(5):1423-31 PMID: 7275946
- 3. Satomura T et al.. 2018. Enzymological characteristics of a novel archaeal dye-linked D-lactate dehydrogenase showing loose binding of FAD.. Extremophiles 22(6):975-981 PMID: 30206766
- 4. Satomura T et al.. 2008. A novel flavin adenine dinucleotide (FAD) containing d-lactate dehydrogenase from the thermoacidophilic crenarchaeota Sulfolobus tokodaii strain 7: purification, characterization and expression in Escherichia coli.. J Biosci Bioeng 106(1):16-21 PMID: 18691525
- 5. Reed DW et al.. 1999. The Archaeoglobus fulgidus D-lactate dehydrogenase is a Zn(2+) flavoprotein.. J Bacteriol 181(24):7580-7 PMID: 10601217
- 6. Stefan A et al.. 2024. The catalytic action of human d-lactate dehydrogenase is severely inhibited by oxalate and is impaired by mutations triggering d-lactate acidosis.. Arch Biochem Biophys 754:109932 PMID: 38373542
- 7. Olson ST et al.. 1979. Purification and properties of the flavoenzyme D-lactate dehydrogenase from Megasphaera elsdenii.. Biochemistry 18(21):4714-24 PMID: 497162
- 8. Jiang T et al.. 2017. 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 199(22) PMID: 28847921
