GO:0160308 succinate dehydrogenase (FAD) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0160308 succinate dehydrogenase (FAD) activity is a molecular function defined as catalysis of the reaction FAD + succinate + H+ = fumarate + FADH2.
• The enzyme is the flavoprotein subunit of mitochondrial complex II (succinate dehydrogenase), which couples succinate oxidation to the respiratory chain.
• FAD is covalently attached to the flavoprotein subunit in many organisms, but covalent attachment is not strictly required for mitochondrial import and assembly in Saccharomyces cerevisiae.
• Loss of succinate dehydrogenase activity causes succinate accumulation, which can act as an oncometabolite and drive tumorigenesis in cancer.
• Defects in succinate dehydrogenase flavoprotein assembly or FAD delivery impair complex II activity and have been linked to mitochondrial disease such as Leigh syndrome spectrum.
• CRISPR knockout, point-mutation, knock-in and overexpression models enable causal testing of SDH genes in cancer, metabolic disease and mitochondrial disorders.
Description
Succinate dehydrogenase (FAD) activity (GO:0160308) is a molecular function that catalyzes the oxidation of succinate to fumarate using FAD as the electron acceptor, producing FADH2. This activity is carried out by the flavoprotein subunit of succinate dehydrogenase (SDH), also known as mitochondrial complex II, which is unique among respiratory chain complexes because it participates directly in the tricarboxylic acid (TCA) cycle. The reaction is central to cellular energy metabolism and to the redox balance of the mitochondrial matrix. Researchers study GO:0160308 because its dysfunction leads to succinate accumulation, altered oxygen sensing, and metabolic reprogramming in cancer and mitochondrial disease. The flavoprotein subunit requires FAD as a cofactor, and in many organisms the cofactor is covalently bound, although covalent attachment is not universally essential for assembly in yeast. Understanding the catalytic mechanism, assembly factors, and regulatory context of this activity is therefore important for both basic mitochondrial biology and translational research.
succinate dehydrogenase (FAD) activity At A Glance
| GO ID | GO:0160308 |
|---|---|
| GO term | succinate dehydrogenase (FAD) activity |
| Ontology | molecular_function |
| Synonym | none |
| Definition | Catalysis of the reaction: FAD + succinate + H+ = fumarate + FADH2 |
| Major function | Oxidation of succinate to fumarate with reduction of FAD to FADH2 in the TCA cycle and respiratory chain |
| Cofactor | FAD (flavin adenine dinucleotide), often covalently attached to the flavoprotein subunit |
| Representative subunit | SDHA (flavoprotein subunit) in mitochondrial complex II |
| Related assembly factor | SDHAF2 is required for assembly and activity of complex II in Arabidopsis |
| Disease relevance | Succinate dehydrogenase loss and succinate accumulation are implicated in cancer and mitochondrial disease |
What Is GO:0160308?
In plain terms, GO:0160308 succinate dehydrogenase (FAD) activity describes the catalytic function of an enzyme that removes electrons from succinate and transfers them to FAD, converting succinate to fumarate and FAD to FADH2. The reaction is reversible in some contexts, but the canonical direction in the TCA cycle is succinate oxidation. This activity is distinct from other succinate dehydrogenases that use different electron acceptors, because the definition explicitly specifies FAD as the acceptor.
Why Is succinate dehydrogenase (FAD) activity Important in Cell Biology?
GO:0160308 is important because it defines the catalytic core of succinate dehydrogenase, an enzyme that links the TCA cycle to oxidative phosphorylation and whose dysfunction alters cellular metabolism, redox state, and signaling. Loss of this activity causes succinate accumulation, which can inhibit prolyl hydroxylases and stabilize HIF-1alpha, contributing to tumorigenesis and metabolic reprogramming. In mitochondrial disease, impaired complex II assembly or FAD delivery reduces succinate dehydrogenase activity and can present as Leigh syndrome spectrum disorders. Because the flavoprotein subunit requires FAD and specific assembly factors, perturbations in riboflavin metabolism or assembly factor function can also affect this activity. Thus, GO:0160308 is a focal point for studies of cancer metabolism, mitochondrial biology, and inherited metabolic disorders.
• Defines the catalytic step that oxidizes succinate to fumarate in the TCA cycle.
• Couples succinate oxidation to FAD reduction, feeding electrons into the respiratory chain.
• Succinate accumulation due to loss of activity can act as an oncometabolite.
• Mutations or assembly defects in complex II are linked to Leigh syndrome spectrum and mitochondrial disease.
• FAD delivery and covalent flavinylation influence enzyme assembly and activity.
• Riboflavin deficiency can impair FAD-dependent enzymes including succinate dehydrogenase.
• Assembly factor SDHAF2 is required for complex II activity in plants, highlighting conserved assembly requirements.
• The activity is a target for metabolic and cancer research using CRISPR models.
• Understanding the mechanism informs development of inhibitors and metabolic probes.
• It provides a functional readout for mitochondrial health in cell models.
Molecular Mechanism of succinate dehydrogenase (FAD) activity
Substrate binding and succinate oxidation
In simple terms: The enzyme grabs succinate and pulls electrons off it.
The flavoprotein subunit of succinate dehydrogenase binds succinate in its active site and catalyzes its oxidation to fumarate. This step is part of the TCA cycle and requires the flavin cofactor to accept the electrons. The reaction is defined as FAD + succinate + H+ = fumarate + FADH2, meaning that FAD is reduced to FADH2 as succinate is oxidized.
FAD cofactor and covalent flavinylation
In simple terms: FAD is the helper molecule that catches electrons, and it is often attached tightly to the enzyme.
FAD is the electron acceptor in this reaction and is typically bound to the flavoprotein subunit. In many organisms, FAD is covalently attached to the protein, but studies in Saccharomyces cerevisiae showed that covalent attachment of FAD to the flavoprotein of succinate dehydrogenase is not necessary for import and assembly into mitochondria. The mitochondrial FAD transporter Flx1p is involved in supplying FAD for flavoprotein subunit expression in yeast.
Electron transfer to the respiratory chain
In simple terms: After FAD is reduced, the electrons are passed down the respiratory chain.
The FADH2 produced by succinate dehydrogenase (FAD) activity donates electrons to the respiratory chain via complex II, linking the TCA cycle to oxidative phosphorylation. This electron transfer is a key function of mitochondrial complex II and distinguishes succinate dehydrogenase from other TCA cycle enzymes.
Assembly and assembly factors
In simple terms: Helper proteins make sure the enzyme is built correctly.
Assembly of active complex II requires specific assembly factors. In Arabidopsis, succinate dehydrogenase assembly factor 2 (SDHAF2) is needed for assembly and activity of mitochondrial complex II and for normal root elongation. In yeast, the mitochondrial FAD transporter Flx1p is involved in expression of the flavoprotein subunit, indicating that FAD availability affects assembly.
Reversibility and fumarate reductase
In simple terms: Some related enzymes can run the reaction backwards.
The reaction catalyzed by succinate dehydrogenase (FAD) activity is related to fumarate reductase, which catalyzes the reverse reaction in some organisms. Catalysis in fumarate reductase has been studied to understand the mechanism of succinate oxidation and fumarate reduction. This relationship highlights the mechanistic conservation of flavin-dependent succinate/fumarate interconversion.
Key Genes Involved in GO:0160308 succinate dehydrogenase (FAD) activity
The following genes and proteins are directly implicated in succinate dehydrogenase (FAD) activity, its assembly, or its regulation, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SDHA | Flavoprotein subunit that catalyzes succinate oxidation using FAD | Core catalytic subunit of GO:0160308; target for cancer and mitochondrial disease studies |
| SDHB | Iron-sulfur subunit of complex II | Required for electron transfer from FADH2 to ubiquinone; mutations linked to disease |
| SDHC | Membrane anchor subunit of complex II | Structural subunit; mutations associated with cancer and mitochondrial disorders |
| SDHD | Membrane anchor subunit of complex II | Structural subunit; mutations associated with cancer and mitochondrial disorders |
| SDHAF1 | Assembly factor for complex II | Required for assembly and activity of complex II |
| SDHAF2 | Assembly factor for complex II | Needed for assembly and activity of mitochondrial complex II in Arabidopsis |
| FLX1 | Mitochondrial FAD transporter in yeast | Involved in flavoprotein subunit expression and FAD supply |
| FAD synthase | Enzyme that produces FAD | Supports FAD availability for succinate dehydrogenase |
| Riboflavin transporter | Uptake of riboflavin, a FAD precursor | Riboflavin deficiency can impair FAD-dependent enzymes |
| HIF1A | Transcription factor stabilized by succinate accumulation | Downstream effector of succinate dehydrogenase loss in cancer |
| PHD | Prolyl hydroxylases inhibited by succinate | Mediate oxygen sensing and are affected by succinate levels |
| Complex II subunits | Structural and catalytic components of mitochondrial complex II | Assemble with SDHA to form active enzyme |
| Mitochondrial import machinery | Imports SDHA into mitochondria | Required for assembly of active succinate dehydrogenase |
| FAD covalent attachment machinery | Attaches FAD to flavoprotein | Covalent flavinylation is common but not essential in yeast |
| TCA cycle enzymes | Coordinate flux with succinate dehydrogenase | Provide substrate succinate and consume fumarate |
| Respiratory chain components | Accept electrons from FADH2 | Link succinate oxidation to oxidative phosphorylation |
How Is succinate dehydrogenase (FAD) activity Regulated?
Succinate dehydrogenase (FAD) activity is regulated at multiple levels. FAD availability influences flavoprotein subunit expression and assembly, as shown by the involvement of the mitochondrial FAD transporter Flx1p in Saccharomyces cerevisiae. Covalent attachment of FAD to the flavoprotein is common but not strictly required for mitochondrial import and assembly in yeast, indicating that regulation of assembly can occur independently of covalent flavinylation. Assembly factors such as SDHAF2 are required for assembly and activity of complex II, providing a regulatory checkpoint. Riboflavin deficiency can limit FAD synthesis and thereby impair FAD-dependent enzymes including succinate dehydrogenase. In cancer, loss of succinate dehydrogenase activity leads to succinate accumulation, which can inhibit prolyl hydroxylases and stabilize HIF-1alpha, creating a feedback loop that alters cellular metabolism.
succinate dehydrogenase (FAD) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SDHA | Mitochondrial disease, cancer | CRISPR knockout in cancer cell lines; point mutation to mimic patient variants |
| SDHB | Paraganglioma, pheochromocytoma | Knockout and knock-in models to study succinate accumulation |
| SDHC | Hereditary paraganglioma | Knockout cell models to assess complex II activity |
| SDHD | Hereditary paraganglioma | Knockout and overexpression models |
| SDHAF2 | Complex II assembly defect | Knockout in plant and mammalian cells to study assembly |
Succinate dehydrogenase loss in cancer
Loss of succinate dehydrogenase (FAD) activity causes succinate accumulation, which can act as an oncometabolite by inhibiting prolyl hydroxylases and stabilizing HIF-1alpha. This metabolic rewiring is observed in cancers with mutations in SDH subunits and contributes to tumorigenesis. Metabolic effects of succinate dehydrogenase loss in cancer include changes in TCA cycle flux and redox balance.
Mitochondrial disease and Leigh syndrome spectrum
Defects in complex II, including the flavoprotein subunit that carries GO:0160308, can cause mitochondrial disease presenting as Leigh syndrome spectrum. Nuclear gene-encoded Leigh syndrome spectrum disorders include mutations in genes required for oxidative phosphorylation and mitochondrial assembly. Impaired succinate dehydrogenase activity reduces respiratory chain function and can lead to neurological and metabolic symptoms.
Riboflavin deficiency and FAD-dependent enzymes
Riboflavin deficiency reduces FAD availability, which can impair FAD-dependent enzymes such as succinate dehydrogenase. Because GO:0160308 requires FAD as a cofactor, conditions that limit riboflavin uptake or FAD synthesis may reduce enzyme activity. This links nutritional status to mitochondrial function.
Assembly factor defects
Mutations or loss of assembly factors such as SDHAF2 impair assembly and activity of mitochondrial complex II, reducing succinate dehydrogenase (FAD) activity. In Arabidopsis, SDHAF2 is needed for complex II activity and normal root elongation, demonstrating the importance of assembly factors for the enzyme. Similar assembly defects in humans can contribute to mitochondrial disease.
From succinate dehydrogenase (FAD) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of SDHA reduce succinate dehydrogenase (FAD) activity? | CRISPR knockout of SDHA in cancer cell lines |
| Does a specific SDHA point mutation impair catalysis? | Point-mutation knock-in of the mutation in a cell line |
| Does restoration of SDHA rescue complex II activity? | Knock-in or overexpression of wild-type SDHA |
| How does SDHAF2 loss affect complex II assembly? | CRISPR knockout of SDHAF2 in Arabidopsis or mammalian cells |
| Does FAD transporter loss affect flavoprotein expression? | Knockout of FLX1 in Saccharomyces cerevisiae |
| Can covalent flavinylation be removed without losing assembly? | Point mutation of the flavinylation site in yeast |
How to Study the succinate dehydrogenase (FAD) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzymatic assay | Succinate dehydrogenase (FAD) activity | Validate knockout or point-mutation effects |
| Metabolomics | Succinate and TCA cycle intermediates | Assess metabolic consequences of SDH loss |
| Western blot | Flavoprotein subunit expression | Confirm knockout or overexpression |
| Mitochondrial import assay | Import and assembly of SDHA | Study covalent flavinylation requirement |
| CRISPR library screen | Genes affecting succinate levels or complex II activity | Discover modifiers of GO:0160308 |
| RNA-seq | Transcriptional changes after SDH loss | Identify downstream pathways |
| Proteomics | Complex II subunit composition | Assess assembly defects |
| Imaging | Mitochondrial morphology and function | Link activity to cellular phenotype |
Enzymatic activity assays
Succinate dehydrogenase (FAD) activity can be measured by monitoring the reduction of FAD or artificial electron acceptors in the presence of succinate. These assays provide direct evidence of catalytic function and are used to validate CRISPR models.
Metabolic profiling
Loss of succinate dehydrogenase activity leads to succinate accumulation, which can be detected by metabolomics. Metabolic profiling of TCA cycle intermediates helps link genotype to metabolic phenotype.
Protein assembly and import studies
Mitochondrial import and assembly of the flavoprotein subunit can be studied using yeast genetics and biochemical fractionation. The role of FAD transporters can be assessed by monitoring flavoprotein expression.
Genetic screens and CRISPR libraries
CRISPR library screening can identify genes that modify succinate dehydrogenase activity or succinate levels. Such screens are useful for discovering assembly factors and metabolic regulators.
How CRISPR Can Be Used to Study GO:0160308 succinate dehydrogenase (FAD) activity
Knockout
CRISPR knockout of SDHA or other complex II subunits eliminates succinate dehydrogenase (FAD) activity, causing succinate accumulation and metabolic rewiring. Knockout models are used to study cancer metabolism and mitochondrial dysfunction.
Point Mutation
Point mutations in SDHA can be introduced to mimic patient variants and test their effect on catalysis. Such models help distinguish loss-of-function from hypomorphic alleles.
Knock-in
Knock-in of wild-type or tagged SDHA allows rescue and localization studies. Tagged knock-in can be used to monitor assembly and interactions.
Overexpression
Overexpression of SDHA or assembly factors can increase complex II activity and rescue defects. Overexpression models are useful for testing sufficiency of a gene in restoring GO:0160308.
How EDITGENE Supports succinate dehydrogenase (FAD) activity Research
Researchers studying succinate dehydrogenase (FAD) activity-related genes often need to determine whether a candidate gene is causally involved in the catalytic function, assembly, or regulation of complex II. EDITGENE provides CRISPR-based cell models and screening services to enable such causal experiments.
Contact EDITGENE today to design your custom CRISPR model for succinate dehydrogenase (FAD) activity research.
Frequently Asked Questions About succinate dehydrogenase (FAD) activity
What is succinate dehydrogenase (FAD) activity?
It is a molecular function defined as catalysis of the reaction FAD + succinate + H+ = fumarate + FADH2, carried out by the flavoprotein subunit of succinate dehydrogenase.
What genes are involved in succinate dehydrogenase (FAD) activity?
Key genes include SDHA, SDHB, SDHC, SDHD, SDHAF1, SDHAF2, and in yeast FLX1, which affect complex II assembly and activity.
What is the GO ID for succinate dehydrogenase (FAD) activity?
The GO ID is GO:0160308.
What is the definition of GO:0160308?
The definition is catalysis of the reaction FAD + succinate + H+ = fumarate + FADH2.
Why is succinate dehydrogenase (FAD) activity important in cancer?
Loss of this activity causes succinate accumulation, which can act as an oncometabolite and stabilize HIF-1alpha, contributing to tumorigenesis.
How is succinate dehydrogenase (FAD) activity measured?
It can be measured by enzymatic assays monitoring FAD reduction or electron acceptor reduction in the presence of succinate.
Is covalent FAD attachment required for succinate dehydrogenase activity?
In Saccharomyces cerevisiae, covalent attachment of FAD to the flavoprotein is not necessary for import and assembly into mitochondria.
What diseases are linked to succinate dehydrogenase (FAD) activity?
Mutations affecting complex II are linked to Leigh syndrome spectrum and mitochondrial disease, and loss of activity is linked to cancer.
What is the role of SDHAF2 in succinate dehydrogenase activity?
SDHAF2 is an assembly factor needed for assembly and activity of mitochondrial complex II, as shown in Arabidopsis.
How can CRISPR be used to study succinate dehydrogenase (FAD) activity?
CRISPR knockout, point mutation, knock-in, and overexpression models can test causal roles of SDH genes in this activity.
Conclusion
GO:0160308 succinate dehydrogenase (FAD) activity defines the catalytic function of the flavoprotein subunit of complex II, a key enzyme linking the TCA cycle to oxidative phosphorylation. Its dysfunction causes succinate accumulation and is implicated in cancer and mitochondrial disease. Understanding its mechanism, assembly, and regulation requires integrated genetic, biochemical, and metabolic approaches. CRISPR-based models provide powerful tools to dissect these processes and to identify therapeutic opportunities.
References
- 1. Adam MP et al.. 1993. Nuclear Gene-Encoded Leigh Syndrome Spectrum Overview.. PMID: 26425749
- 2. Chatoff A et al.. 2025. Metabolic Effects of Succinate Dehydrogenase Loss in Cancer.. J Cell Physiol 240(7):e70066 PMID: 40685935
- 3. Barber MJ et al.. 1987. Anti-flavin antibodies.. Biochem J 242(1):89-95 PMID: 3109386
- 4. Sina RE et al.. 2026. Riboflavin Deficiency.. PMID: 29262062
- 5. Huang S et al.. 2013. Succinate dehydrogenase assembly factor 2 is needed for assembly and activity of mitochondrial complex II and for normal root elongation in Arabidopsis.. Plant J 73(3):429-41 PMID: 23036115
- 6. Giancaspero TA et al.. 2008. Succinate dehydrogenase flavoprotein subunit expression in Saccharomyces cerevisiae--involvement of the mitochondrial FAD transporter, Flx1p.. FEBS J 275(6):1103-17 PMID: 18279395
- 7. Robinson KM et al.. 1994. The covalent attachment of FAD to the flavoprotein of Saccharomyces cerevisiae succinate dehydrogenase is not necessary for import and assembly into mitochondria.. Eur J Biochem 222(3):983-90 PMID: 8026509
- 8. Reid GA et al.. 2000. Catalysis in fumarate reductase.. Biochim Biophys Acta 1459(2-3):310-5 PMID: 11004445
