GO:0052874 FMN reductase (NADH) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0052874 (FMN reductase (NADH) activity) catalyzes the reaction FMNH2 + NAD+ = FMN + NADH + 2 H+, enabling NADH-dependent reduction of flavin mononucleotide.
• The activity is widely distributed in bacteria, yeast, and mammals, where it supports respiratory chains, detoxification, and reductive metabolism.
• Several NADH-dependent reductases that use FMN as a cofactor have been structurally and biochemically characterized, including thermostable indigo reductase and acrylate reductase.
• Dihydropteridine reductase (DHPR) exhibits NADH-ferric reductase activity, linking FMN-dependent redox chemistry to iron homeostasis.
• NADH:quinone oxidoreductases and cytochrome P450cin systems illustrate the broad physiological roles of FMN-dependent NADH oxidation.
• CRISPR-based knockout, point-mutation, knock-in, and overexpression models are essential to dissect the cellular functions of FMN reductase (NADH) activity.
Description
FMN reductase (NADH) activity, classified under GO:0052874, is a molecular function that catalyzes the NADH-dependent reduction of flavin mononucleotide (FMN) to its reduced form, FMNH2, while oxidizing NADH to NAD+. This redox reaction is fundamental to many biological processes, including electron transport, detoxification of reactive species, and the activation of flavin-dependent enzymes. The term is synonymous with NADH dehydrogenase (FMN) activity, NADH-dependent FMN reductase activity, and NADH-FMN reductase activity, reflecting its central role in cellular redox balance. Researchers study this activity to understand how cells maintain flavin homeostasis and how disruptions contribute to disease and metabolic disorders. The enzyme is found across all domains of life, from bacterial respiratory chains to mammalian ferric reductases, underscoring its evolutionary conservation and functional versatility.
FMN reductase (NADH) activity At A Glance
| GO ID | GO:0052874 |
|---|---|
| GO term | FMN reductase (NADH) activity |
| Ontology | molecular_function |
| Synonym | NADH dehydrogenase (FMN) activity; NADH-dependent FMN reductase activity; NADH-FMN reductase activity |
| Major function | Catalyzes the NADH-dependent reduction of FMN to FMNH2 |
| Reaction | FMNH2 + NAD+ = FMN + NADH + 2 H+ |
| Cofactor | Flavin mononucleotide (FMN) |
| Cellular context | Respiratory chains, detoxification, reductive metabolism |
What Is GO:0052874?
In our own words, GO:0052874 describes the catalytic activity of an enzyme that transfers electrons from NADH to FMN, producing FMNH2 and NAD+. This reaction is reversible and involves the uptake of two protons, as summarized by the equation FMNH2 + NAD+ = FMN + NADH + 2 H+. The activity is typically associated with flavoproteins that contain FMN as a tightly bound cofactor and is essential for maintaining the reduced flavin pool required by various metabolic pathways.
Why Is FMN reductase (NADH) activity Important in Cell Biology?
FMN reductase (NADH) activity is critical for cellular redox homeostasis, energy metabolism, and the function of numerous flavoenzymes. By regenerating FMNH2, it supports processes such as iron uptake, detoxification of reactive oxygen species, and the biosynthesis of complex molecules. Dysregulation of this activity has been linked to bacterial pathogenesis, yeast metabolism, and potential roles in human diseases involving oxidative stress.
• Maintains the reduced flavin pool necessary for flavoenzyme catalysis.
• Supports bacterial respiratory chains and energy production.
• Contributes to iron homeostasis through ferric reductase activity.
• Plays a role in detoxification of reactive oxygen species.
• Involved in the activation of cytochrome P450cin in bacterial systems.
• Enables reductive metabolism of environmental compounds like acrylate and cinnamate.
• Potential target for antimicrobial development due to its role in bacterial respiration.
• Relevant to metabolic engineering for production of reduced flavin-dependent products.
• May influence oxidative stress responses in human cells.
• Provides a model for studying flavin-based redox regulation across species.
What Happens During FMN reductase (NADH) activity?
Substrate Binding and Electron Transfer
In simple terms: The enzyme grabs NADH and FMN, then passes electrons from NADH to FMN.
The catalytic cycle begins with the binding of NADH and FMN to the enzyme's active site. NADH donates a hydride ion to the flavin ring of FMN, resulting in the formation of FMNH2 and NAD+. This step is facilitated by conserved residues that stabilize the transition state and orient the substrates for efficient electron transfer.
Proton Uptake and Product Release
In simple terms: Two protons are taken up, and the products FMNH2 and NAD+ are released.
Following hydride transfer, the enzyme undergoes conformational changes that allow the uptake of two protons from the solvent, completing the reduction of FMN to FMNH2. The reduced flavin is then released or channeled to downstream partners, while NAD+ dissociates, regenerating the free enzyme for another round of catalysis.
Physiological Context and Coupling
In simple terms: This reaction is part of larger pathways like respiration and detoxification.
In bacterial respiratory chains, FMN reductase (NADH) activity is coupled to quinone reduction and proton pumping, contributing to the proton motive force. In yeast, a similar activity is associated with NADH-cytochrome c reductase, linking flavin reduction to mitochondrial electron transport. In mammals, dihydropteridine reductase exhibits NADH-ferric reductase activity, connecting flavin chemistry to iron metabolism.
Regulation by Redox State
In simple terms: The enzyme's activity can be turned up or down depending on the cell's redox balance.
The activity of FMN reductase (NADH) is sensitive to the NAD+/NADH ratio and the availability of oxidized FMN. Under oxidative stress, increased NADH levels can stimulate the enzyme to regenerate FMNH2, which acts as an antioxidant. In some bacteria, the expression of FMN-dependent reductases is regulated by redox-sensing transcription factors, ensuring appropriate responses to environmental changes.
Key Genes Involved in GO:0052874 FMN reductase (NADH) activity
The following genes and proteins are experimentally linked to FMN reductase (NADH) activity or its physiological roles.
| Gene | Major Role | Research Relevance |
|---|---|---|
| DHPR | Dihydropteridine reductase with NADH-ferric reductase activity | Links FMN chemistry to iron homeostasis |
| NDH-1 | Bacterial NADH-quinone oxidoreductase | Model for respiratory chain FMN reduction |
| Indigo reductase | Thermostable FMN-dependent NADH-indigo reductase | Biotechnological applications |
| CYP176A1 | Cytochrome P450cin requiring FMN reductase for activity | Bacterial detoxification |
| Acrylate reductase | NADH-dependent acrylate reductase in Vibrio harveyi | Environmental metabolism |
| Cinnamate reductase | Heterodimeric NADH:cinnamate reductase in Vibrio ruber | Redox regulation |
| NADH-cytochrome c reductase | FMN-containing enzyme from yeast | Mitochondrial electron transport |
| Cupric reductase | NADH-linked cupric reductase from E. coli | Copper homeostasis |
| Fre | FMN reductase in E. coli | Model for flavin reduction |
| NfsA | Oxygen-insensitive NADPH nitroreductase | Related flavin reductase |
| NfsB | NADH-dependent nitroreductase | Prodrug activation |
| Mtr | Mycothiol disulfide reductase | Redox homeostasis |
| RibD | Bifunctional riboflavin biosynthesis protein | FMN production |
| RibF | FMN reductase in riboflavin biosynthesis | Flavin metabolism |
| YhdA | Putative FMN reductase | Genomic studies |
| YieF | Chromate reductase with FMN activity | Bioremediation |
| NQO1 | NAD(P)H:quinone oxidoreductase | Cancer and detoxification |
How Is FMN reductase (NADH) activity Regulated?
The activity of FMN reductase (NADH) is regulated at multiple levels. In bacteria, redox-sensing transcription factors such as OxyR and SoxRS modulate the expression of genes encoding FMN-dependent reductases in response to oxidative stress. In yeast, the activity is influenced by the mitochondrial NAD+/NADH ratio and by the availability of flavin cofactors. In mammals, dihydropteridine reductase activity can be affected by iron levels and oxidative conditions, suggesting post-translational regulation. Additionally, the heterodimeric cinnamate reductase in Vibrio ruber is regulated by redox state, with its activity peaking under anaerobic conditions.
FMN reductase (NADH) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| DHPR | Hyperphenylalaninemia, iron dyshomeostasis | Knockout mouse, patient-derived fibroblasts |
| NQO1 | Cancer susceptibility, detoxification | CRISPR knockout in cancer cell lines |
| Fre | Bacterial respiration, oxidative stress | E. coli knockout and overexpression |
| Acrylate reductase | Environmental metabolism, pathogenesis | Vibrio harveyi knockout |
| Cinnamate reductase | Redox regulation, infection | Vibrio ruber mutant models |
FMN reductase (NADH) activity and Oxidative Stress
Altered FMN reductase (NADH) activity can disrupt cellular redox balance, leading to increased oxidative stress. In E. coli, the NADH-linked cupric reductase activity contributes to copper homeostasis, and its dysregulation may enhance sensitivity to oxidative damage. In humans, dihydropteridine reductase deficiency causes hyperphenylalaninemia, a metabolic disorder with neurological consequences, partly due to impaired ferric reductase activity.
Roles in Bacterial Pathogenesis
Bacterial pathogens rely on FMN-dependent reductases for respiration and detoxification. For example, Vibrio harveyi uses an NADH-dependent acrylate reductase to metabolize environmental acrylate, which may contribute to its survival in host tissues. Similarly, Vibrio ruber employs a redox-regulated cinnamate reductase, potentially aiding in adaptation to varying oxygen levels during infection.
Potential Links to Cancer and Metabolic Disorders
While direct links to cancer are not well established, FMN-dependent enzymes like NQO1 are known to play roles in detoxification and cancer susceptibility. The NADH-ferric reductase activity of DHPR may influence iron metabolism, which is implicated in neurodegenerative diseases and cancer. Further research is needed to clarify these connections.
From FMN reductase (NADH) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the catalytic mechanism of FMN reductase? | Point mutations in active-site residues |
| How does loss of FMN reductase affect bacterial growth? | Knockout in E. coli or Vibrio species |
| Can FMN reductase be redirected to new substrates? | Directed evolution with knock-in libraries |
| What are the interacting partners of FMN reductase? | Tagged knock-in for affinity purification |
| Does overexpression protect against oxidative stress? | Overexpression in mammalian cell lines |
| How is FMN reductase regulated at the transcriptional level? | Reporter knock-in and RNA-seq |
How to Study the FMN reductase (NADH) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| NADH oxidation assay | Enzyme activity | Kinetic characterization |
| X-ray crystallography | Three-dimensional structure | Active-site mapping |
| RNA-seq | Gene expression changes | Stress response studies |
| CRISPR knockout library | Gene essentiality | Functional genomics |
| Affinity purification-MS | Protein interactions | Interactome mapping |
| Site-directed mutagenesis | Residue function | Mechanistic studies |
| High-throughput screening | Inhibitor identification | Drug discovery |
Enzymatic Assays
Direct measurement of FMN reductase (NADH) activity is typically performed by monitoring the oxidation of NADH at 340 nm or the reduction of FMN using spectrophotometric or fluorometric methods. These assays can be adapted for high-throughput screening to identify inhibitors or activators.
Structural Biology
X-ray crystallography and cryo-EM have been used to determine the structures of FMN-dependent reductases, revealing key active-site residues and conformational changes during catalysis. These studies provide a framework for rational drug design and protein engineering.
Genomic and Transcriptomic Approaches
RNA-seq and transcriptomic profiling can reveal how expression of FMN reductase genes changes under different conditions, such as oxidative stress or infection. CRISPR-based knockout libraries enable systematic interrogation of gene function in relevant pathways.
Proteomics and Interactomics
Affinity purification coupled with mass spectrometry can identify protein-protein interactions involving FMN reductases, shedding light on their cellular partners and regulatory networks. Tagged knock-in models facilitate these studies in native contexts.
How CRISPR Can Be Used to Study GO:0052874 FMN reductase (NADH) activity
Knockout
CRISPR knockout of genes encoding FMN reductase (NADH) activity, such as DHPR or bacterial fre, can reveal their essentiality and impact on respiration, oxidative stress resistance, and metabolism. Knockout cell lines are valuable for studying loss-of-function phenotypes and compensatory pathways.
Point Mutation
Introducing point mutations in catalytic residues of FMN reductases allows precise dissection of the reaction mechanism. For example, mutating the conserved histidine or arginine involved in hydride transfer can abolish activity, confirming their roles.
Knock-in
Knock-in of tagged versions of FMN reductase genes (e.g., GFP or FLAG) enables real-time imaging and affinity purification, facilitating studies of localization, dynamics, and interactions. This approach is particularly useful for tracking the enzyme under different physiological conditions.
Overexpression
Overexpression of FMN reductase (NADH) in bacterial or mammalian cells can enhance reduced flavin pools, potentially protecting against oxidative stress or increasing production of reduced metabolites. This strategy is also used to study gain-of-function effects and for biotechnological applications.
How EDITGENE Supports FMN reductase (NADH) activity Research
Researchers studying FMN reductase (NADH) activity-related genes often need to determine whether a candidate gene is causally involved in redox regulation, metabolism, or disease. EDITGENE provides comprehensive CRISPR services to accelerate this discovery process.
Contact EDITGENE today to design your custom CRISPR model for FMN reductase (NADH) activity research.
Frequently Asked Questions About FMN reductase (NADH) activity
What is FMN reductase (NADH) activity?
It is a molecular function (GO:0052874) that catalyzes the NADH-dependent reduction of FMN to FMNH2, as defined by the reaction FMNH2 + NAD+ = FMN + NADH + 2 H+.
What genes are involved in FMN reductase (NADH) activity?
Genes include DHPR, bacterial fre, indigo reductase, acrylate reductase, and cinnamate reductase, among others.
What is the role of FMN reductase in bacteria?
It supports respiratory chains, detoxification, and metabolism of environmental compounds like acrylate and cinnamate.
How is FMN reductase (NADH) activity measured?
Common methods include NADH oxidation assays, spectrophotometric monitoring at 340 nm, and fluorometric detection of FMN reduction.
Is FMN reductase (NADH) activity linked to human disease?
Dihydropteridine reductase deficiency, which affects ferric reductase activity, causes hyperphenylalaninemia; other links are under investigation.
What are the synonyms for GO:0052874?
Synonyms include NADH dehydrogenase (FMN) activity, NADH-dependent FMN reductase activity, and NADH-FMN reductase activity.
Can CRISPR be used to study FMN reductase (NADH) activity?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models are powerful tools to dissect gene function.
What is the reaction catalyzed by FMN reductase (NADH)?
The reaction is FMNH2 + NAD+ = FMN + NADH + 2 H+, representing the oxidation of FMNH2 and reduction of NAD+.
Which organisms have FMN reductase (NADH) activity?
It is found in bacteria, yeast, and mammals, reflecting its evolutionary conservation.
How does oxidative stress affect FMN reductase (NADH) activity?
Oxidative stress can increase NADH levels and stimulate the enzyme to regenerate FMNH2, which acts as an antioxidant.
Conclusion
FMN reductase (NADH) activity (GO:0052874) is a fundamental redox reaction that sustains flavin homeostasis, respiratory chains, and detoxification across diverse organisms. Its broad distribution and critical roles in bacterial pathogenesis, yeast metabolism, and human metabolic disorders make it an attractive target for research and therapeutic development. Leveraging CRISPR-based models and advanced biochemical assays will continue to unravel its mechanistic details and physiological significance.
References
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- 2. Yagi T. 1991. Bacterial NADH-quinone oxidoreductases.. J Bioenerg Biomembr 23(2):211-25 PMID: 2050655
- 3. Yoneda K et al.. 2020. Structural and biochemical characterization of an extremely thermostable FMN-dependent NADH-indigo reductase from Bacillus smithii.. Int J Biol Macromol 164:3259-3267 PMID: 32861785
- 4. Stok JE et al.. 2015. Cytochrome P450cin (CYP176A1).. Adv Exp Med Biol 851:319-39 PMID: 26002741
- 5. Bertsova YV et al.. 2022. A Novel, NADH-Dependent Acrylate Reductase in Vibrio harveyi.. Appl Environ Microbiol 88(11):e0051922 PMID: 35612301
- 6. Bertsova YV et al.. 2024. A Redox-Regulated, Heterodimeric NADH:cinnamate Reductase in Vibrio ruber.. Biochemistry (Mosc) 89(2):241-256 PMID: 38622093
- 7. Johnson MS et al.. 1985. Studies on NADH (NADPH)-cytochrome c reductase (FMN-containing) from yeast. Isolation and physicochemical properties of the enzyme from top-fermenting ale yeast.. J Biol Chem 260(22):12341-50 PMID: 3930493
- 8. Rapisarda VA et al.. 1999. Characterization of an NADH-linked cupric reductase activity from the Escherichia coli respiratory chain.. Arch Biochem Biophys 370(2):143-50 PMID: 10510271
