GO:0106281 chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0106281 describes the NAD+-dependent oxidation of chenodeoxycholate to 7-oxolithocholate, a key bile-acid transformation in microbial and hepatic metabolism.
• The reaction is catalyzed by 7-alpha-hydroxysteroid dehydrogenases (7α-HSDHs), enzymes that are often induced by bile acids in gut bacteria such as Clostridium and Bacteroides species.
• This activity is central to the conversion of primary bile acids into secondary bile acids, influencing host lipid absorption, energy homeostasis, and inflammation.
• Dysregulation of bile-acid metabolism, including 7α-dehydrogenation, has been linked to alcoholic liver disease and other hepatic pathologies.
• Structural and functional studies of acidophilic 7α-HSDHs reveal conserved catalytic residues and cofactor-binding motifs that can be targeted for inhibitor design.
• CRISPR-based knockout, point-mutation, and knock-in models enable precise interrogation of 7α-HSDH genes in bile-acid metabolism and disease.
Description
Chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity (GO:0106281) is a molecular function that catalyzes the reversible oxidation of chenodeoxycholate to 7-oxolithocholate, using NAD+ as an electron acceptor. This reaction is a critical step in the microbial and hepatic conversion of primary bile acids into secondary bile acids, which are important signaling molecules and metabolic regulators. The enzyme responsible, 7-alpha-hydroxysteroid dehydrogenase (7α-HSDH), has been identified in a variety of anaerobic gut bacteria, including Clostridium and Bacteroides species, where it is often induced by bile acids. The reaction is also relevant to peroxisomal bile-acid synthesis in the liver, where 7α-HSDH activity contributes to the formation of chenodeoxycholic acid from precursors. Understanding this activity is essential for researchers studying bile-acid metabolism, host-microbiome interactions, and liver disease.
chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity At A Glance
| GO ID | GO:0106281 |
|---|---|
| GO term | chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity |
| Ontology | molecular_function |
| Synonym | (none) |
| Major function | Catalyzes the NAD+-dependent oxidation of chenodeoxycholate to 7-oxolithocholate |
| Reaction | chenodeoxycholate + NAD+ = 7-oxolithocholate + H+ + NADH |
| Cofactor | NAD+ |
| Substrate | chenodeoxycholate |
| Product | 7-oxolithocholate |
What Is GO:0106281?
According to the Gene Ontology, GO:0106281 is defined as the catalysis of the reaction: chenodeoxycholate + NAD+ = 7-oxolithocholate + H+ + NADH. In other words, it is the NAD+-dependent oxidation of the 7-alpha-hydroxyl group of chenodeoxycholate, producing 7-oxolithocholate and NADH. This activity is a subset of 7-alpha-hydroxysteroid dehydrogenase (7α-HSDH) activities, which can use either NAD+ or NADP+ as cofactors.
Why Is chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity Important in Cell Biology?
GO:0106281 is important because it represents a key enzymatic step in bile-acid metabolism, influencing the balance between primary and secondary bile acids. These molecules act as signaling molecules that regulate lipid, glucose, and energy homeostasis, and their dysregulation is implicated in liver diseases, metabolic disorders, and gastrointestinal cancers. The activity also plays a role in the gut microbiome, where bacterial 7α-HSDHs modify host bile acids, affecting host physiology and disease susceptibility. Therefore, understanding this activity provides insights into host-microbe interactions and potential therapeutic targets.
• Regulates the conversion of chenodeoxycholate to 7-oxolithocholate, a secondary bile acid with distinct signaling properties.
• Influences bile-acid pool composition, which affects lipid digestion and absorption.
• Modulates farnesoid X receptor (FXR) signaling, a nuclear receptor that controls bile-acid synthesis and transport.
• Contributes to the pathogenesis of alcoholic liver disease through altered bile-acid metabolism.
• Represents a target for modulating gut microbiota to improve metabolic health.
• Provides a model for studying enzyme-cofactor specificity and catalytic mechanisms.
• Enables the production of secondary bile acids that can act as tumor promoters or suppressors in colon cancer.
• Serves as a biomarker for microbial bile-acid transformation in the gut.
• Offers a potential drug target for treating bile-acid-related disorders.
• Facilitates the development of engineered probiotics or enzymes for bile-acid modulation.
Molecular Mechanism of chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity
Substrate Binding and Recognition
In simple terms: The enzyme grabs chenodeoxycholate and holds it in place.
The enzyme 7-alpha-hydroxysteroid dehydrogenase (7α-HSDH) binds chenodeoxycholate in a specific pocket that positions the 7-alpha-hydroxyl group for oxidation. Structural studies of acidophilic 7α-HSDH reveal a conserved substrate-binding site with residues that interact with the steroid nucleus and the carboxylate side chain. The binding is stereospecific, ensuring that only the 7-alpha epimer is oxidized.
Cofactor Binding and Hydride Transfer
In simple terms: NAD+ accepts a hydride ion from the substrate.
NAD+ binds to the enzyme's Rossmann-fold domain, positioning the nicotinamide ring near the substrate's 7-alpha-hydroxyl group. The catalytic reaction involves the transfer of a hydride from the substrate to NAD+, forming NADH and a ketone intermediate at C7 of the steroid. This step is rate-limiting and requires a deprotonated hydroxyl group, which is facilitated by a catalytic base.
Product Release and Enzyme Turnover
In simple terms: The products leave, and the enzyme is ready for another round.
After hydride transfer, 7-oxolithocholate and NADH are released from the active site. The enzyme can then bind a new molecule of chenodeoxycholate and NAD+ to continue catalysis. The reaction is reversible, and the equilibrium can be influenced by the concentrations of substrates and products.
Regulation by Bile Acids
In simple terms: Bile acids can turn on the production of this enzyme.
In bacteria such as Clostridium absonum and Clostridium limosum, the expression of 7-alpha- and 7-beta-hydroxysteroid dehydrogenases is induced by bile acids in the growth medium. This induction allows the bacteria to adapt to the presence of bile and modify bile acids for their own benefit. The regulation likely involves bile-acid-responsive promoters or regulatory proteins.
Physiological Role in Bile-Acid Metabolism
In simple terms: This reaction helps convert primary bile acids into secondary ones.
By oxidizing chenodeoxycholate to 7-oxolithocholate, this activity contributes to the formation of secondary bile acids such as lithocholic acid. In the liver, 7α-HSDH activity is involved in the peroxisomal formation of chenodeoxycholic acid from 3-alpha,7-alpha-dihydroxy-5-beta-cholestanoic acid. The balance between primary and secondary bile acids affects host metabolism and disease.
Key Genes Involved in GO:0106281 chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity
The following genes and proteins are directly or indirectly associated with chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| 7α-HSDH (Clostridium absonum) | Bile-acid inducible 7-alpha-hydroxysteroid dehydrogenase | Model for bile-acid induction and enzyme regulation |
| 7α-HSDH (Clostridium limosum) | Bile-acid inducible 7-alpha-hydroxysteroid dehydrogenase | Studied for bile-acid transformation and induction |
| 7α-HSDH (Bacteroides fragilis) | NAD-dependent 7-alpha-hydroxysteroid dehydrogenase | Prototype for NAD specificity and gut microbial bile-acid metabolism |
| 7α-HSDH (Clostridium bifermentans) | Oxidizes primary bile acids | Soil isolate enzyme for bile-acid oxidation |
| Acidophilic 7α-HSDH | Novel acidophilic 7-alpha-hydroxysteroid dehydrogenase | Structural and functional characterization for biotechnology |
| FXR (NR1H4) | Nuclear receptor regulating bile-acid homeostasis | Linked to alcoholic liver disease and bile-acid signaling |
| CYP7A1 | Cholesterol 7-alpha-hydroxylase | Rate-limiting enzyme in bile-acid synthesis, indirectly related |
| CYP27A1 | Sterol 27-hydroxylase | Alternative bile-acid synthesis pathway |
| BSEP (ABCB11) | Bile salt export pump | Affects bile-acid pool and feedback regulation |
| NTCP (SLC10A1) | Sodium-taurocholate cotransporting polypeptide | Hepatic bile-acid uptake |
| ASBT (SLC10A2) | Apical sodium-dependent bile-acid transporter | Intestinal bile-acid absorption |
| OSTα/β | Organic solute transporter | Bile-acid efflux from enterocytes |
| FGF19 | Fibroblast growth factor 19 | Regulates bile-acid synthesis via FXR |
| SHP (NR0B2) | Small heterodimer partner | Represses bile-acid synthesis genes |
| LRH-1 (NR5A2) | Liver receptor homolog-1 | Activates bile-acid synthesis genes |
| HNF4α | Hepatocyte nuclear factor 4 alpha | Regulates bile-acid transporters and enzymes |
How Is chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity Regulated?
The expression and activity of 7-alpha-hydroxysteroid dehydrogenases can be regulated by bile acids themselves. In Clostridium absonum and Clostridium limosum, the presence of bile acids in the growth medium induces the production of 7-alpha- and 7-beta-hydroxysteroid dehydrogenases. This induction is likely mediated by bile-acid-responsive regulatory elements, although the exact molecular mechanisms remain to be fully elucidated. In the host, bile-acid signaling through the farnesoid X receptor (FXR) regulates genes involved in bile-acid synthesis, transport, and metabolism, indirectly affecting the availability of substrates for 7α-HSDH. Additionally, the redox state of the cell, reflected by NAD+/NADH ratios, can influence the direction and rate of the reaction catalyzed by 7α-HSDH.
chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| FXR (NR1H4) | Alcoholic liver disease, cholestasis | Liver-specific FXR knockout mice |
| 7α-HSDH (Bacteroides fragilis) | Colorectal cancer, bile-acid metabolism | Gnotobiotic mice colonized with wild-type vs. mutant strains |
| 7α-HSDH (Clostridium absonum) | Bile-acid transformation, gut dysbiosis | In vitro enzyme assays and bacterial cultures |
| Acidophilic 7α-HSDH | Biotechnological applications, drug targeting | Recombinant enzyme expression and structural studies |
| CYP7A1 | Hypercholesterolemia, bile-acid diarrhea | Cyp7a1 knockout mice |
Alcoholic Liver Disease
Alcoholic liver disease is associated with altered bile-acid metabolism, including changes in the composition of the bile-acid pool. The farnesoid X receptor (FXR) plays a central role in regulating bile-acid homeostasis, and its dysfunction contributes to the pathogenesis of alcoholic liver disease. The activity of 7-alpha-hydroxysteroid dehydrogenases can influence the levels of secondary bile acids, which may exacerbate liver injury or affect regeneration. Targeting this activity could provide therapeutic strategies for alcoholic liver disease.
Colorectal Cancer
Secondary bile acids, such as deoxycholic acid and lithocholic acid, have been implicated in colorectal carcinogenesis. The conversion of chenodeoxycholate to 7-oxolithocholate by 7-alpha-hydroxysteroid dehydrogenases is a step in the formation of secondary bile acids. Elevated levels of secondary bile acids can promote DNA damage and cell proliferation in the colon, potentially increasing cancer risk. Therefore, inhibiting bacterial 7α-HSDH activity might reduce the production of tumor-promoting bile acids.
Metabolic Disorders
Bile acids are signaling molecules that regulate glucose and lipid metabolism through receptors such as FXR and TGR5. Alterations in bile-acid composition, including the ratio of primary to secondary bile acids, have been linked to obesity, insulin resistance, and type 2 diabetes. The activity of 7-alpha-hydroxysteroid dehydrogenases can modulate this ratio, thereby influencing metabolic homeostasis. Modulating the gut microbiota to alter 7α-HSDH activity is a potential therapeutic approach for metabolic disorders.
From chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of 7α-HSDH affect bile-acid pool composition? | Knockout of bacterial 7α-HSDH in gnotobiotic mice |
| How does a point mutation in the active site affect catalysis? | Site-directed mutagenesis of recombinant 7α-HSDH |
| Can a tagged 7α-HSDH be used to track localization? | Knock-in of FLAG- or GFP-tagged 7α-HSDH in bacteria |
| What is the effect of 7α-HSDH overexpression on bile-acid metabolism? | Overexpression of 7α-HSDH in E. coli or Lactobacillus |
| Does FXR signaling modulate 7α-HSDH activity? | FXR knockout mice treated with bile acids |
| Can CRISPR screening identify regulators of 7α-HSDH expression? | CRISPR library screening in bacterial or mammalian cells |
How to Study the chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Spectrophotometric NADH assay | Enzyme activity by NADH production | Kinetic characterization of 7α-HSDH |
| LC-MS bile-acid profiling | Concentrations of bile acids | Quantifying chenodeoxycholate and 7-oxolithocholate in samples |
| X-ray crystallography | Three-dimensional structure | Determining active site and cofactor binding |
| Site-directed mutagenesis | Effect of specific mutations on activity | Identifying catalytic residues |
| 16S rRNA sequencing | Microbial community composition | Linking bacteria to bile-acid metabolism |
| CRISPR-Cas9 knockout | Gene function | Disrupting 7α-HSDH genes in bacteria or cells |
| CRISPR library screening | Genes affecting a phenotype | Identifying regulators of 7α-HSDH expression |
| Recombinant protein expression | Purified enzyme for assays | Biochemical and structural studies |
Enzymatic Assays
Enzymatic activity of 7-alpha-hydroxysteroid dehydrogenase can be measured spectrophotometrically by monitoring the reduction of NAD+ to NADH at 340 nm. This method allows determination of kinetic parameters such as Km and Vmax, and can be used to screen inhibitors or activators. Radioactive or mass spectrometry-based assays can also be employed to detect the formation of 7-oxolithocholate.
Structural Biology
X-ray crystallography and cryo-electron microscopy can provide high-resolution structures of 7α-HSDH in complex with substrates, cofactors, and inhibitors. These structures reveal the catalytic mechanism and guide the design of specific inhibitors. Site-directed mutagenesis combined with structural analysis can validate the roles of key residues.
Microbiome and Metabolomics
16S rRNA sequencing and metagenomics can identify bacteria harboring 7α-HSDH genes in the gut microbiome. Metabolomics, particularly bile-acid profiling using LC-MS, can quantify the levels of chenodeoxycholate and 7-oxolithocholate in biological samples. These approaches link microbial composition to bile-acid transformation.
CRISPR-Cas9 Genome Editing
CRISPR-Cas9 can be used to knock out or mutate 7α-HSDH genes in bacterial strains or mammalian cells to study their function. Knock-in of tagged versions allows localization and interaction studies. Library screening can identify host or microbial genes that regulate 7α-HSDH expression or activity.
How CRISPR Can Be Used to Study GO:0106281 chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity
Knockout
CRISPR-Cas9 knockout of 7α-HSDH genes in bacterial strains such as Bacteroides fragilis or Clostridium species can abolish the conversion of chenodeoxycholate to 7-oxolithocholate. This allows researchers to study the impact of this activity on bile-acid pool composition and host physiology in gnotobiotic mouse models. Knockout of host genes involved in bile-acid signaling, such as FXR, can also modulate the expression of 7α-HSDH.
Point Mutation
Introducing point mutations in the catalytic residues of 7α-HSDH (e.g., the catalytic base or NAD+ binding residues) can reveal their roles in catalysis and substrate specificity. For example, mutating the conserved tyrosine or lysine in the active site can reduce or abolish activity, confirming their importance. Such mutants can be expressed in E. coli and characterized biochemically.
Knock-in
Knock-in of epitope tags (e.g., FLAG, His6) or fluorescent proteins (e.g., GFP) into the endogenous 7α-HSDH locus allows real-time tracking of enzyme expression and localization in live cells or bacteria. This can be combined with super-resolution microscopy to study enzyme dynamics. Knock-in of reporter genes under the control of the 7α-HSDH promoter can be used to monitor induction by bile acids.
Overexpression
Overexpression of 7α-HSDH in E. coli or Lactobacillus species can be used to produce large quantities of the enzyme for structural and biochemical studies. It can also be used to engineer probiotic strains with enhanced bile-acid-modifying capabilities, potentially for therapeutic applications. Overexpression in mammalian cells can help study the effects of increased 7α-HSDH activity on bile-acid signaling and metabolism.
How EDITGENE Supports chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity Research
Researchers studying chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity-related genes often need to determine whether a candidate gene is causally involved in bile-acid metabolism, microbial transformation, or disease. EDITGENE provides a comprehensive suite of CRISPR-based services to enable precise genome editing and functional genomics in this field.
Contact EDITGENE today to design your custom CRISPR model for chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity research.
Frequently Asked Questions About chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity
What is chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity?
It is a molecular function (GO:0106281) that catalyzes the NAD+-dependent oxidation of chenodeoxycholate to 7-oxolithocholate, a key step in bile-acid metabolism.
What genes are involved in chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity?
Genes encoding 7-alpha-hydroxysteroid dehydrogenases (7α-HSDHs) from bacteria such as Bacteroides fragilis, Clostridium absonum, and Clostridium limosum, as well as host genes involved in bile-acid signaling like FXR.
What is the reaction catalyzed by GO:0106281?
The reaction is: chenodeoxycholate + NAD+ = 7-oxolithocholate + H+ + NADH.
How is 7-alpha-hydroxysteroid dehydrogenase activity regulated?
In bacteria, it can be induced by bile acids. In host, bile-acid signaling through FXR regulates related genes.
What diseases are associated with chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity?
Alcoholic liver disease, colorectal cancer, and metabolic disorders have been linked to altered bile-acid metabolism involving this activity.
How can I study chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity in the lab?
Enzymatic assays, LC-MS bile-acid profiling, structural biology, and CRISPR-based genome editing are common approaches.
What model systems are available for studying this activity?
Bacterial cultures, gnotobiotic mice, recombinant enzyme expression, and CRISPR knockout/knock-in cell lines.
What is the role of NAD+ in this reaction?
NAD+ acts as an electron acceptor, being reduced to NADH during the oxidation of chenodeoxycholate.
Can CRISPR be used to study chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity?
Yes, CRISPR-Cas9 can knock out, mutate, or knock in 7α-HSDH genes to study their function and regulation.
Where can I find services for CRISPR knockout of 7α-HSDH genes?
EDITGENE provides custom CRISPR knockout, point mutation, knock-in, overexpression, and library screening services for 7α-HSDH and related genes.
Conclusion
Chenodeoxycholate 7-alpha-dehydrogenase (NAD+) activity (GO:0106281) is a fundamental enzymatic function in bile-acid metabolism, with significant implications for host-microbe interactions, liver disease, and metabolic disorders. Understanding its mechanism, regulation, and role in disease requires robust experimental models, including CRISPR-based genome editing. EDITGENE offers a comprehensive suite of services to support research on this activity, from knockout and point mutation models to library screening and bioinformatics.
References
- 1. Manley S et al.. 2015. Role of farnesoid X receptor and bile acids in alcoholic liver disease.. Acta Pharm Sin B 5(2):158-67 PMID: 26579442
- 3. Sutherland JD et al.. 1987. Oxidation of primary bile acids by a 7 alpha-hydroxysteroid dehydrogenase elaborating Clostridium bifermentans soil isolate.. Can J Microbiol 33(8):663-9 PMID: 3480039
- 4. MacDonald IA et al.. 1981. Bile induction of 7 alpha- and 7 beta-hydroxysteroid dehydrogenases in Clostridium absonum.. Biochim Biophys Acta 665(2):262-9 PMID: 6945134
- 5. Sutherland JD et al.. 1985. Bile acid induction of 7 alpha- and 7 beta-hydroxysteroid dehydrogenases in Clostridium limosum.. J Lipid Res 26(3):344-50 PMID: 3857290
- 6. Prydz K et al.. 1986. Formation of chenodeoxycholic acid from 3 alpha, 7 alpha-dihydroxy-5 beta-cholestanoic acid by rat liver peroxisomes.. J Lipid Res 27(6):622-8 PMID: 3746130
- 7. Tang S et al.. 2019. Structural and functional characterization of a novel acidophilic 7α-hydroxysteroid dehydrogenase.. Protein Sci 28(5):910-919 PMID: 30839141
- 8. Macdonald IA et al.. 1975. NAD- and NADP-dependent 7alpha-hydroxysteroid dehydrogenases from bacteroides fragilis.. Biochim Biophys Acta 384(1):12-24 PMID: 236764
