GO:0006781 succinyl-CoA pathway: Heme Biosynthesis Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0006781 (succinyl-CoA pathway) describes the chemical reactions that use succinyl-CoA to synthesize protoporphyrin IX, the immediate precursor of heme.
• The pathway begins with the condensation of succinyl-CoA and glycine by ALAS, forming delta-aminolevulinic acid, and ends with protoporphyrin IX after seven enzymatic steps.
• Succinyl-CoA is a central metabolic intermediate linking the TCA cycle to heme synthesis, and its availability can influence the rate of protoporphyrin IX production.
• Defects in succinyl-CoA pathway enzymes cause human disorders including sideroblastic anemia, erythropoietic protoporphyria, and X-linked protoporphyria.
• Succinyl-CoA metabolism also supports nuclear and chromatin-related processes, expanding its relevance beyond heme synthesis.
• CRISPR knockout, point-mutation, and knock-in models are powerful tools to dissect the enzymatic steps and regulatory nodes of this pathway.
Description
The succinyl-CoA pathway (GO:0006781) is the set of biochemical reactions that utilize succinyl-CoA for the synthesis of protoporphyrin IX, the final intermediate before heme formation. This pathway is essential for heme biosynthesis in all cells that require heme for respiration, oxygen transport, and oxidative metabolism. Succinyl-CoA, a tricarboxylic acid (TCA) cycle intermediate, is the committed carbon donor for the first step of the pathway, linking central carbon metabolism to porphyrin production. Because heme is indispensable for hemoglobin, cytochromes, and numerous hemoproteins, the succinyl-CoA pathway is a focal point for understanding metabolic regulation and disease. Recent studies have also revealed that succinyl-CoA participates in nuclear metabolic-epigenetic circuits, suggesting broader roles beyond classical heme synthesis. Researchers studying this pathway aim to define how its enzymes are regulated, how mutations cause disease, and how to target it therapeutically.
succinyl-CoA pathway At A Glance
| GO ID | GO:0006781 |
|---|---|
| GO term | succinyl-CoA pathway |
| Ontology | biological_process |
| Synonym | biosynthesis of protoporphyrin IX via succinyl-CoA; succinyl CoA pathway |
| Major function | Synthesis of protoporphyrin IX from succinyl-CoA and glycine |
| Pathway steps | Eight enzymatic reactions from succinyl-CoA to protoporphyrin IX |
| Key enzymes | ALAS, ALAD, HMBS, UROS, UROD, CPOX, PPOX, FECH |
| Cellular location | Mitochondria and cytosol (enzymes distributed across compartments) |
| Related diseases | Sideroblastic anemia, porphyrias, erythropoietic protoporphyria |
What Is GO:0006781?
GO:0006781 (succinyl-CoA pathway) is defined by QuickGO as the chemical reactions that utilize succinyl-CoA in the synthesis of protoporphyrin IX. In other words, it is the metabolic route that starts with succinyl-CoA and glycine and proceeds through a series of enzymatic steps to produce protoporphyrin IX, the immediate precursor of heme. This pathway is a subprocess of heme biosynthesis and is synonymous with biosynthesis of protoporphyrin IX via succinyl-CoA.
Why Is succinyl-CoA pathway Important in Cell Biology?
The succinyl-CoA pathway is essential for heme biosynthesis, and thus for fundamental processes such as oxygen transport, mitochondrial respiration, and drug metabolism. Its first enzyme, ALAS, catalyzes the rate-limiting step, making the pathway a key regulatory node in erythroid and hepatic cells. Dysregulation of succinyl-CoA metabolism has been linked to ineffective erythropoiesis in myelodysplastic syndromes, and succinyl-CoA-based energy metabolism is impaired in chronic heart failure. Moreover, succinyl-CoA is a substrate for nuclear histone succinylation and lactylation, connecting this pathway to epigenetic regulation and cancer. Therefore, understanding GO:0006781 provides insights into metabolic, hematologic, and oncologic diseases.
• Provides the essential precursor protoporphyrin IX for heme, which is required for hemoglobin, myoglobin, and cytochromes.
• Links TCA cycle intermediate succinyl-CoA to porphyrin synthesis, integrating carbon metabolism with heme production.
• Mutations in pathway enzymes cause sideroblastic anemia and various porphyrias.
• Succinyl-CoA availability influences erythropoiesis, as shown in SF3B1-mutated myelodysplasia.
• Succinyl-CoA-based energy metabolism is dysfunctional in chronic heart failure.
• Nuclear succinyl-CoA metabolism contributes to histone modifications and gene regulation.
• The pathway is a target for treating porphyrias and for developing anti-cancer strategies.
• CRISPR screens can identify modifiers of the pathway and potential therapeutic targets.
What Happens During succinyl-CoA pathway?
Step 1: Formation of delta-aminolevulinic acid (ALA)
In simple terms: The pathway starts by joining succinyl-CoA and glycine to make a molecule called ALA.
The first and rate-limiting step of the succinyl-CoA pathway is the condensation of succinyl-CoA with glycine to form delta-aminolevulinic acid (ALA), catalyzed by delta-aminolevulinic acid synthase (ALAS) in the mitochondrial matrix. This reaction requires pyridoxal 5'-phosphate as a cofactor and releases CoA and CO2. ALAS exists in two isoforms: the erythroid-specific ALAS2 and the ubiquitous ALAS1. Because this step consumes succinyl-CoA, the pathway is directly dependent on TCA cycle activity and succinyl-CoA availability.
Step 2: Synthesis of porphobilinogen
In simple terms: Two ALA molecules are combined to form porphobilinogen, a key building block.
In the cytosol, two molecules of ALA are condensed by delta-aminolevulinic acid dehydratase (ALAD) to form porphobilinogen (PBG). This enzyme is inhibited by lead and its deficiency causes ALAD porphyria. PBG is the first pyrrole intermediate in the pathway and is the substrate for the next steps.
Step 3: Formation of hydroxymethylbilane
In simple terms: Four porphobilinogen units are linked together to make a linear tetrapyrrole.
Four molecules of porphobilinogen are polymerized by hydroxymethylbilane synthase (HMBS, also known as PBGD) to form the linear tetrapyrrole hydroxymethylbilane (HMB). This reaction occurs in the cytosol and releases ammonia. Deficiency of HMBS causes acute intermittent porphyria.
Step 4: Cyclization to uroporphyrinogen III
In simple terms: The linear molecule is closed into a ring to form uroporphyrinogen III.
Hydroxymethylbilane is cyclized by uroporphyrinogen III synthase (UROS) to form uroporphyrinogen III, the first cyclic tetrapyrrole in the pathway. In the absence of UROS, HMB spontaneously cyclizes to uroporphyrinogen I, a non-physiological isomer. UROS deficiency causes congenital erythropoietic porphyria.
Step 5: Decarboxylation to coproporphyrinogen III
In simple terms: Side chains on the ring are trimmed to make coproporphyrinogen III.
Uroporphyrinogen III is decarboxylated by uroporphyrinogen decarboxylase (UROD) to form coproporphyrinogen III. This enzyme removes four carboxyl groups from the acetate side chains, converting them to methyl groups. UROD deficiency leads to porphyria cutanea tarda and hepatoerythropoietic porphyria.
Step 6: Oxidation to protoporphyrinogen IX
In simple terms: The molecule is further modified to protoporphyrinogen IX.
Coproporphyrinogen III is transported into the mitochondria and oxidized by coproporphyrinogen oxidase (CPOX) to protoporphyrinogen IX. This step removes two propionate groups and releases CO2. CPOX deficiency causes hereditary coproporphyria.
Step 7: Formation of protoporphyrin IX
In simple terms: The final step in the succinyl-CoA pathway produces protoporphyrin IX.
Protoporphyrinogen IX is oxidized by protoporphyrinogen oxidase (PPOX) to protoporphyrin IX, the end product of the succinyl-CoA pathway. This reaction removes six hydrogen atoms and requires molecular oxygen. PPOX deficiency causes variegate porphyria. Protoporphyrin IX is then chelated with ferrous iron by ferrochelatase (FECH) to form heme, which is the subsequent step outside GO:0006781.
Key Genes Involved in GO:0006781 succinyl-CoA pathway
The following genes encode enzymes and related proteins that participate in or regulate the succinyl-CoA pathway (GO:0006781).
| Gene | Major Role | Research Relevance |
|---|---|---|
| ALAS1 | Ubiquitous delta-aminolevulinic acid synthase; catalyzes first step | Regulated by heme and circadian rhythms; target for porphyria |
| ALAS2 | Erythroid-specific delta-aminolevulinic acid synthase | Mutations cause X-linked sideroblastic anemia |
| ALAD | Delta-aminolevulinic acid dehydratase; forms porphobilinogen | Deficiency causes ALAD porphyria; inhibited by lead |
| HMBS | Hydroxymethylbilane synthase; polymerizes PBG | Deficiency causes acute intermittent porphyria |
| UROS | Uroporphyrinogen III synthase; cyclizes HMB | Deficiency causes congenital erythropoietic porphyria |
| UROD | Uroporphyrinogen decarboxylase; decarboxylates uroporphyrinogen III | Deficiency causes porphyria cutanea tarda |
| CPOX | Coproporphyrinogen oxidase; oxidizes coproporphyrinogen III | Deficiency causes hereditary coproporphyria |
| PPOX | Protoporphyrinogen oxidase; forms protoporphyrin IX | Deficiency causes variegate porphyria |
| FECH | Ferrochelatase; inserts iron into protoporphyrin IX (downstream) | Deficiency causes erythropoietic protoporphyria |
| SLC25A38 | Mitochondrial glycine transporter; supplies glycine for ALA synthesis | Mutations cause sideroblastic anemia |
| GTPSCS | Succinyl-CoA synthetase; produces succinyl-CoA | Nuclear isoform functions as lactyl-CoA synthetase in glioma |
| SUCLA2 | Succinyl-CoA ligase subunit; TCA cycle enzyme | Deficiency affects mitochondrial DNA and heme synthesis |
| SUCLG1 | Succinyl-CoA ligase subunit; TCA cycle enzyme | Mutations cause mitochondrial DNA depletion syndrome |
| SF3B1 | Splicing factor; mutated in myelodysplasia | Vitamin B5 and succinyl-CoA improve erythropoiesis in SF3B1-mutated MDS |
| SIRT5 | Desuccinylase; regulates succinylation | Modulates succinyl-CoA metabolism and chromatin |
| EP300 | Histone acetyltransferase; uses acetyl-CoA | Links acyl-CoA metabolism to chromatin |
| KAT2A | Histone acetyltransferase; succinyltransferase | Uses succinyl-CoA for histone succinylation |
How Is succinyl-CoA pathway Regulated?
The succinyl-CoA pathway is regulated at multiple levels. The first step, catalyzed by ALAS, is rate-limiting and subject to feedback inhibition by heme, which represses ALAS1 transcription and inhibits ALAS1 activity. In erythroid cells, ALAS2 is regulated by iron availability and erythropoietin signaling. Succinyl-CoA availability, determined by TCA cycle flux and succinyl-CoA synthetase activity, also influences pathway flux. Additionally, post-translational modifications such as succinylation and lactylation of histones and other proteins link succinyl-CoA metabolism to epigenetic regulation. In chronic heart failure, succinyl-CoA-based energy metabolism is impaired, suggesting that metabolic stress can dysregulate the pathway. In SF3B1-mutated myelodysplasia, supplementation with vitamin B5 and succinyl-CoA improves ineffective erythropoiesis, indicating that substrate availability is a regulatory node.
succinyl-CoA pathway and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| ALAS2 | X-linked sideroblastic anemia | Knockout or point-mutation in erythroid cells |
| HMBS | Acute intermittent porphyria | Knockout mouse or patient-derived iPSCs |
| UROD | Porphyria cutanea tarda | Liver-specific knockout or overexpression |
| SF3B1 | Myelodysplastic syndrome with ring sideroblasts | Knock-in of SF3B1 mutations in hematopoietic stem cells |
| GTPSCS | Glioma (via histone lactylation) | Knockout or overexpression in glioma cell lines |
Porphyrias and Heme Biosynthesis Disorders
Mutations in enzymes of the succinyl-CoA pathway cause a group of inherited disorders known as porphyrias. For example, ALAD deficiency causes ALAD porphyria, HMBS deficiency causes acute intermittent porphyria, UROS deficiency causes congenital erythropoietic porphyria, UROD deficiency causes porphyria cutanea tarda, CPOX deficiency causes hereditary coproporphyria, and PPOX deficiency causes variegate porphyria. These diseases are characterized by accumulation of porphyrin intermediates that cause neurovisceral and cutaneous symptoms. Additionally, mutations in ALAS2 cause X-linked sideroblastic anemia, and mutations in SLC25A38 cause sideroblastic anemia due to impaired glycine supply.
Myelodysplastic Syndromes and Ineffective Erythropoiesis
In myelodysplastic syndromes with SF3B1 mutations, ineffective erythropoiesis is associated with impaired succinyl-CoA metabolism. Treatment with vitamin B5 and succinyl-CoA improves erythropoiesis in these patients, highlighting the role of the succinyl-CoA pathway in red blood cell production. This suggests that targeting the pathway could be a therapeutic strategy for anemia in MDS.
Cardiometabolic Disease
Succinyl-CoA-based energy metabolism is dysfunctional in chronic heart failure. Studies in animal models and human samples show that succinyl-CoA levels and related enzyme activities are altered, contributing to mitochondrial dysfunction. This links the succinyl-CoA pathway to cardiac pathology and suggests that modulating succinyl-CoA metabolism could be beneficial in heart failure.
Cancer and Epigenetic Regulation
Nuclear GTPSCS functions as a lactyl-CoA synthetase to promote histone lactylation and gliomagenesis, connecting succinyl-CoA metabolism to cancer. Succinyl-CoA is also used for histone succinylation, which regulates gene expression. These findings indicate that the succinyl-CoA pathway can influence tumorigenesis through epigenetic mechanisms, making it a potential target for cancer therapy.
From succinyl-CoA pathway-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of ALAS2 impair heme synthesis? | ALAS2 knockout cell line (e.g., K562) |
| Does a specific point mutation in HMBS cause acute intermittent porphyria? | HMBS point-mutation knock-in in HEK293 or iPSCs |
| Can overexpression of UROD rescue porphyria cutanea tarda phenotypes? | UROD overexpression in hepatocyte-like cells |
| How does succinyl-CoA availability affect erythropoiesis? | SF3B1-mutated MDS model treated with succinyl-CoA |
| What is the role of nuclear GTPSCS in histone lactylation? | GTPSCS knockout or tagged knock-in in glioma cells |
| Does SIRT5 regulate succinylation of pathway enzymes? | SIRT5 knockout or overexpression in cell lines |
How to Study the succinyl-CoA pathway Process
| Method | What It Measures | Typical Application |
|---|---|---|
| CRISPR knockout screen | Gene essentiality and synthetic lethality | Identify modifiers of succinyl-CoA pathway |
| Metabolomics (LC-MS) | Levels of succinyl-CoA, ALA, porphyrins | Assess pathway flux in disease models |
| RNA-seq | Gene expression changes | Measure pathway gene transcription |
| Proteomics | Protein abundance and modifications | Detect succinylation/lactylation |
| Enzyme activity assays | Catalytic activity of ALAS, HMBS, etc. | Validate mutations in patient samples |
| Heme quantification | Heme levels | Assess pathway output |
| Flow cytometry | Erythroid differentiation | Evaluate erythropoiesis in MDS models |
| Chromatin immunoprecipitation (ChIP) | Histone modification occupancy | Study epigenetic regulation |
CRISPR-Cas9 Knockout Screens
Genome-wide CRISPR knockout screens can identify genes that are essential for succinyl-CoA pathway activity or that modify disease phenotypes. For example, screens in SF3B1-mutated cells could reveal synthetic lethal interactions with the pathway. Such screens typically use pooled sgRNA libraries and next-generation sequencing to quantify sgRNA enrichment or depletion.
Metabolomics and Flux Analysis
Mass spectrometry-based metabolomics can quantify succinyl-CoA, ALA, porphobilinogen, and porphyrin intermediates to assess pathway flux. Stable isotope tracing with 13C-labeled succinyl-CoA or glycine can measure carbon flow through the pathway. These methods are essential for understanding how mutations or treatments affect pathway activity.
RNA Sequencing and Transcriptomics
RNA-seq can measure expression levels of succinyl-CoA pathway genes (e.g., ALAS1, ALAS2, HMBS) under different conditions or in patient samples. Differential expression analysis can reveal regulatory mechanisms and identify biomarkers.
Proteomics and Post-Translational Modification Analysis
Proteomic approaches can detect succinylation, acetylation, and lactylation of pathway enzymes and histones. Antibodies specific for succinyl-lysine or lactyl-lysine can be used in Western blotting or immunoprecipitation. These methods link succinyl-CoA metabolism to epigenetic regulation.
How CRISPR Can Be Used to Study GO:0006781 succinyl-CoA pathway
Knockout
CRISPR knockout of succinyl-CoA pathway genes (e.g., ALAS2, HMBS, UROD) can create cell models to study loss-of-function phenotypes, such as impaired heme synthesis or accumulation of intermediates. These models are useful for drug screening and for validating disease mechanisms.
Point Mutation
Introducing disease-associated point mutations (e.g., in ALAS2 or HMBS) via CRISPR base editing or homology-directed repair allows researchers to study the specific effects of mutations on enzyme activity and pathway flux. Such models can recapitulate human porphyrias or sideroblastic anemia.
Knock-in
Knock-in of tagged versions of pathway enzymes (e.g., GFP-ALAS2) enables live-cell imaging and proteomic analysis of protein interactions and localization. Knock-in of reporter genes under pathway promoters can monitor pathway activity in real time.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression can increase expression of pathway genes to study gain-of-function effects, such as enhanced heme synthesis or protection against stress. Overexpression of UROD or FECH may rescue phenotypes in disease models.
How EDITGENE Supports succinyl-CoA pathway Research
Researchers studying succinyl-CoA pathway-related genes often need to determine whether a candidate gene is causally involved in heme synthesis, metabolic regulation, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to create precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for succinyl-CoA pathway research.
Frequently Asked Questions About succinyl-CoA pathway
What is the succinyl-CoA pathway (GO:0006781)?
The succinyl-CoA pathway is the set of biochemical reactions that use succinyl-CoA to synthesize protoporphyrin IX, the precursor of heme.
What genes are involved in the succinyl-CoA pathway?
Key genes include ALAS1, ALAS2, ALAD, HMBS, UROS, UROD, CPOX, PPOX, and FECH, which encode the enzymes of the pathway.
What is the role of succinyl-CoA in heme synthesis?
Succinyl-CoA condenses with glycine to form delta-aminolevulinic acid (ALA), the first committed step in heme synthesis.
Which diseases are associated with defects in the succinyl-CoA pathway?
Defects cause porphyrias (e.g., acute intermittent porphyria, porphyria cutanea tarda) and sideroblastic anemia.
How is the succinyl-CoA pathway regulated?
It is regulated by heme feedback inhibition, iron availability, and succinyl-CoA supply from the TCA cycle.
What is the first step of the succinyl-CoA pathway?
The first step is the condensation of succinyl-CoA and glycine to form ALA, catalyzed by ALAS.
What is the end product of the succinyl-CoA pathway?
The end product is protoporphyrin IX, which is then converted to heme by ferrochelatase.
Can CRISPR be used to study the succinyl-CoA pathway?
Yes, CRISPR knockout, point mutation, and knock-in models can be used to dissect gene function and disease mechanisms in this pathway.
What is the connection between succinyl-CoA and cancer?
Nuclear GTPSCS uses succinyl-CoA to produce lactyl-CoA, promoting histone lactylation and gliomagenesis.
How does succinyl-CoA metabolism affect erythropoiesis?
In SF3B1-mutated myelodysplasia, vitamin B5 and succinyl-CoA improve ineffective erythropoiesis.
Conclusion
The succinyl-CoA pathway (GO:0006781) is a fundamental metabolic route for heme biosynthesis, with critical roles in erythroid development, mitochondrial function, and epigenetic regulation. Its dysfunction underlies a spectrum of diseases, from porphyrias to sideroblastic anemia and cancer. Advances in CRISPR-based genome editing and multi-omics technologies are enabling precise dissection of this pathway, offering new opportunities for therapeutic intervention. Continued research into the succinyl-CoA pathway will illuminate basic metabolic principles and translate into clinical benefits.
References
- 1. Liu R et al.. 2025. Nuclear GTPSCS functions as a lactyl-CoA synthetase to promote histone lactylation and gliomagenesis.. Cell Metab 37(2):377-394.e9 PMID: 39642882
- 2. Trefely S et al.. 2020. Compartmentalised acyl-CoA metabolism and roles in chromatin regulation.. Mol Metab 38:100941 PMID: 32199817
- 3. Takada S et al.. 2022. Succinyl-CoA-based energy metabolism dysfunction in chronic heart failure.. Proc Natl Acad Sci U S A 119(41):e2203628119 PMID: 36201541
- 4. Mian SA et al.. 2023. Vitamin B5 and succinyl-CoA improve ineffective erythropoiesis in SF3B1-mutated myelodysplasia.. Sci Transl Med 15(685):eabn5135 PMID: 36857430
- 5. Ogun AS et al.. 2026. Biochemistry, Heme Synthesis.. PMID: 30726014
- 8. Liu X et al.. 2021. The existence of a nonclassical TCA cycle in the nucleus that wires the metabolic-epigenetic circuitry.. Signal Transduct Target Ther 6(1):375 PMID: 34728602
