GO:0047743 chlordecone reductase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0047743 chlordecone reductase activity catalyzes the NADP+-dependent oxidation of chlordecone alcohol to chlordecone, producing NADPH and H+.
• The enzyme was purified from human liver and identified as a monomeric cytosolic protein with a molecular mass of approximately 37 kDa.
• Chlordecone reductase activity is associated with aldo-keto reductase (AKR) enzymes, particularly AKR1C1 and AKR1C2, which also exhibit 3α-hydroxysteroid dehydrogenase and dihydrodiol dehydrogenase activities [2,4].
• The enzyme is expressed in human liver and other tissues, and its activity can be measured by monitoring NADPH formation or chlordecone alcohol oxidation [1,2].
• Genetic and biochemical studies have linked chlordecone reductase activity to the metabolism of xenobiotics and endogenous steroids, with implications for drug resistance and hormone-dependent diseases [3,5].
• CRISPR-based models (knockout, point mutation, knock-in, overexpression) enable precise dissection of the physiological roles of chlordecone reductase and related AKR genes [6,7,8].
Description
Chlordecone reductase activity (GO:0047743) is a molecular function defined by the reversible oxidation of chlordecone alcohol to chlordecone, coupled to the reduction of NADP+ to NADPH. This activity was first characterized in human liver cytosol, where the enzyme was purified to homogeneity and shown to be a monomer with a molecular weight of about 37 kDa. The reaction is of toxicological interest because chlordecone (Kepone) is a persistent organochlorine pesticide that bioaccumulates and causes neurotoxicity and endocrine disruption in humans and wildlife. The enzyme provides a metabolic route for chlordecone detoxification by converting the alcohol metabolite back to the parent ketone, which can then be further metabolized or excreted. Beyond xenobiotic metabolism, chlordecone reductase activity is structurally and functionally related to aldo-keto reductases (AKRs), particularly AKR1C1 and AKR1C2, which participate in the metabolism of steroid hormones, bile acids, and prostaglandins [4,5]. The dual role of these enzymes in endogenous and exogenous substrate handling makes them attractive targets for studying drug resistance, hormone-dependent cancers, and environmental toxicology [3,5]. This article synthesizes the current knowledge on the mechanism, genes, and research methods for studying GO:0047743, with a focus on CRISPR-based approaches for functional validation.
chlordecone reductase activity At A Glance
| GO ID | GO:0047743 |
|---|---|
| GO term | chlordecone reductase activity |
| Ontology | molecular_function |
| Synonym | CDR activity, chlordecone-alcohol:NADP+ 2-oxidoreductase activity |
| Definition | Catalysis of the reaction: chlordecone alcohol + NADP+ = chlordecone + H+ + NADPH. |
| Major function | Oxidation of chlordecone alcohol to chlordecone, generating NADPH. |
| Cofactor | NADP+ (nicotinamide adenine dinucleotide phosphate) |
| Subcellular location | Cytosol (human liver) |
| Molecular mass | Approximately 37 kDa (monomer) |
| Enzyme class | Oxidoreductase (aldo-keto reductase family) |
What Is GO:0047743?
Chlordecone reductase activity (GO:0047743) is the catalysis of the reaction: chlordecone alcohol + NADP+ = chlordecone + H+ + NADPH. In other words, it is an oxidoreductase that uses NADP+ as an electron acceptor to oxidize chlordecone alcohol to chlordecone, releasing a proton and generating NADPH. The enzyme is also known as CDR or chlordecone-alcohol:NADP+ 2-oxidoreductase.
Why Is chlordecone reductase activity Important in Cell Biology?
Chlordecone reductase activity is important because it represents a key metabolic step in the detoxification of the organochlorine pesticide chlordecone, a persistent environmental pollutant associated with neurotoxicity and endocrine disruption [1,2]. The enzyme's ability to interconvert chlordecone and its alcohol metabolite influences the overall toxicity and clearance of the pesticide. Moreover, chlordecone reductase is a member of the aldo-keto reductase superfamily, which includes enzymes that metabolize steroid hormones, bile acids, and xenobiotics, thereby impacting drug resistance and hormone-dependent diseases [4,5]. Understanding this activity at the molecular level can inform risk assessment and the development of therapeutic strategies for chlordecone exposure and related metabolic disorders [3,5].
• Provides a metabolic pathway for the detoxification of chlordecone, a persistent organic pollutant [1,2].
• Generates NADPH, which is essential for reductive biosynthesis and antioxidant defense.
• Belongs to the aldo-keto reductase family, which includes enzymes involved in steroid hormone metabolism [4,5].
• May influence the pharmacokinetics and toxicity of chlordecone and related organochlorines.
• Has been linked to 3α-hydroxysteroid dehydrogenase and dihydrodiol dehydrogenase activities, affecting hormone-dependent cancers [3,5].
• Serves as a model for studying NADP+-dependent oxidoreductases and their substrate specificity [1,4].
• Can be targeted by CRISPR-based gene editing to dissect its physiological roles [6,7,8].
• Relevant to environmental toxicology and public health in regions contaminated with chlordecone.
• Potential biomarker for susceptibility to chlordecone toxicity.
• Contributes to the understanding of xenobiotic metabolism and drug-drug interactions.
Molecular Mechanism of chlordecone reductase activity
Substrate binding and specificity
In simple terms: The enzyme grabs chlordecone alcohol and NADP+ to start the reaction.
Chlordecone reductase binds its substrate, chlordecone alcohol, and the cofactor NADP+ in a sequential manner. The enzyme exhibits specificity for chlordecone alcohol, but it also accepts other substrates such as 3α-hydroxysteroids and dihydrodiols, reflecting its membership in the aldo-keto reductase family [1,4]. The binding site accommodates the bulky organochlorine structure of chlordecone alcohol, allowing the hydride transfer from the alcohol to NADP+.
Catalytic mechanism
In simple terms: The enzyme removes hydrogen from chlordecone alcohol and gives it to NADP+, making NADPH.
The catalytic mechanism involves a hydride transfer from the alcohol group of chlordecone alcohol to the nicotinamide ring of NADP+, resulting in the formation of chlordecone, NADPH, and a proton. This oxidation reaction is reversible, and the equilibrium can be influenced by the concentrations of substrates and products. The enzyme uses a tyrosine residue as a general acid/base in the catalytic cycle, a common feature of aldo-keto reductases.
Cofactor requirements
In simple terms: The enzyme needs NADP+ as a helper molecule to work.
Chlordecone reductase activity strictly requires NADP+ as the electron acceptor; NAD+ cannot substitute efficiently. The enzyme binds NADP+ with high affinity, and the cofactor remains associated during the catalytic cycle. The NADPH produced can be used in other metabolic pathways, such as reductive biosynthesis or antioxidant defense.
Regulation and inhibition
In simple terms: Other molecules can speed up or slow down the enzyme.
The activity of chlordecone reductase can be modulated by endogenous compounds such as bile acids and steroid hormones, which compete for the active site [4,5]. Inhibitors of aldo-keto reductases, such as flufenamic acid and indomethacin, also inhibit chlordecone reductase activity. The enzyme's expression may be regulated at the transcriptional level by xenobiotic-responsive nuclear receptors, although direct evidence for chlordecone reductase regulation is limited.
Key Genes Involved in GO:0047743 chlordecone reductase activity
The following genes encode enzymes with chlordecone reductase activity or related aldo-keto reductase functions.
| Gene | Major Role | Research Relevance |
|---|---|---|
| AKR1C1 | Chlordecone reductase, 3α-hydroxysteroid dehydrogenase, dihydrodiol dehydrogenase | Key enzyme for chlordecone detoxification and steroid metabolism |
| AKR1C2 | Chlordecone reductase, 3α-hydroxysteroid dehydrogenase, dihydrodiol dehydrogenase | Isoform with high chlordecone reductase activity; associated with bile-acid binding [4,7] |
| AKR1C3 | 3α-hydroxysteroid dehydrogenase, prostaglandin reductase | Related AKR with overlapping substrate specificity |
| AKR1C4 | 3α-hydroxysteroid dehydrogenase | Liver-specific isoform involved in steroid hormone metabolism |
| AKR1B1 | Aldose reductase | Member of AKR superfamily; not a major chlordecone reductase |
| AKR1A1 | Aldehyde reductase | Related enzyme with broad substrate specificity |
| AKR1D1 | 5β-reductase | Steroid 5β-reductase; may interact with chlordecone metabolism |
| AKR1E2 | Unknown function | Poorly characterized AKR family member |
| AKR6A5 | Voltage-gated potassium channel subunit | AKR superfamily member with distinct function |
| AKR7A2 | Aflatoxin B1 aldehyde reductase | Protects against aflatoxin toxicity; not chlordecone reductase |
| CBR1 | Carbonyl reductase 1 | NADPH-dependent reductase with overlapping substrates |
| CBR3 | Carbonyl reductase 3 | Related carbonyl reductase |
| DHRS4 | Dehydrogenase/reductase SDR family member 4 | Short-chain dehydrogenase involved in retinoid metabolism |
| HSD11B1 | 11β-hydroxysteroid dehydrogenase type 1 | Regulates glucocorticoid action; not chlordecone reductase |
| SRD5A1 | Steroid 5α-reductase 1 | Androgen metabolism; unrelated to chlordecone reductase |
| UGT1A1 | UDP-glucuronosyltransferase 1A1 | Phase II enzyme that may conjugate chlordecone metabolites |
| CYP3A4 | Cytochrome P450 3A4 | Oxidizes chlordecone and other xenobiotics |
| ABCB1 | P-glycoprotein | Efflux transporter that may affect chlordecone disposition |
How Is chlordecone reductase activity Regulated?
The regulation of chlordecone reductase activity is not well characterized at the transcriptional level. However, as an aldo-keto reductase, its activity can be influenced by post-translational modifications and by the availability of NADP+. Endogenous inhibitors such as bile acids and steroid hormones can modulate enzyme activity through competitive binding [4,5]. Additionally, expression of AKR1C genes may be regulated by nuclear receptors such as the constitutive androstane receptor (CAR) and pregnane X receptor (PXR), which respond to xenobiotics. Further research is needed to elucidate the precise regulatory mechanisms.
chlordecone reductase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| AKR1C1 | Chlordecone neurotoxicity, hormone-dependent cancers | CRISPR knockout in human hepatocytes or neuronal cells [2,3] |
| AKR1C2 | Bile acid metabolism, breast cancer | Point mutation knock-in in MCF-7 cells [4,7] |
| AKR1C3 | Prostate cancer, drug resistance | Overexpression in LNCaP cells [3,5] |
| AKR1C4 | Liver toxicity, steroid metabolism | Knockout in HepG2 cells |
| AKR1B1 | Diabetic complications | Knock-in of human variant in mouse models |
Chlordecone toxicity and neurotoxicity
Chlordecone (Kepone) is a neurotoxic organochlorine pesticide that causes tremors, memory loss, and motor dysfunction in exposed individuals. Chlordecone reductase activity converts chlordecone alcohol back to chlordecone, potentially prolonging its retention in the body and exacerbating toxicity. Genetic variations in AKR1C genes may influence individual susceptibility to chlordecone neurotoxicity.
Hormone-dependent cancers
AKR1C1 and AKR1C2, which possess chlordecone reductase activity, also catalyze the reduction of steroid hormones such as progesterone and testosterone, thereby influencing hormone signaling [3,5]. Overexpression of these enzymes has been observed in breast, prostate, and endometrial cancers, where they may promote tumor growth by altering local hormone levels [3,5]. Targeting chlordecone reductase activity could therefore have therapeutic potential in hormone-dependent malignancies.
Drug resistance
Aldo-keto reductases, including chlordecone reductase, can metabolize chemotherapeutic agents such as anthracyclines and taxanes, contributing to drug resistance. Inhibiting these enzymes may sensitize cancer cells to chemotherapy. However, the specific role of chlordecone reductase in drug resistance requires further investigation.
From chlordecone reductase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does AKR1C1 knockout reduce chlordecone detoxification? | CRISPR knockout in HepG2 cells |
| Does a point mutation in AKR1C2 alter substrate specificity? | CRISPR point mutation knock-in in HEK293 cells |
| Can overexpression of AKR1C3 confer drug resistance? | CRISPR overexpression in cancer cell lines |
| What is the tissue-specific role of AKR1C4? | Tissue-specific knockout in mouse models |
| Does a tagged AKR1C1 knock-in affect enzyme localization? | CRISPR knock-in of FLAG tag in human cells |
| Can CRISPR library screening identify modifiers of chlordecone toxicity? | Genome-wide CRISPR knockout library in human cells |
How to Study the chlordecone reductase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| NADPH absorbance assay | Enzyme activity | Kinetic studies of chlordecone reductase |
| LC-MS | Substrate and product quantification | Metabolite profiling in biological samples |
| qRT-PCR | mRNA expression levels | Tissue distribution of AKR1C genes |
| Western blot | Protein expression and modification | Validation of knockout or overexpression |
| CRISPR knockout | Gene function loss | Phenotypic analysis of AKR1C genes |
| CRISPR knock-in | Precise mutation introduction | Structure-function studies |
| CRISPR overexpression | Gene gain-of-function | Drug resistance modeling |
| CRISPR library screening | Genome-wide gene function | Identification of modifiers of chlordecone toxicity |
Enzymatic activity assays
Chlordecone reductase activity can be measured spectrophotometrically by monitoring the formation of NADPH at 340 nm or the oxidation of chlordecone alcohol using HPLC or LC-MS. These assays are used to quantify enzyme kinetics and inhibitor potency.
Gene expression analysis
Quantitative RT-PCR and RNA-seq can measure the expression levels of AKR1C genes in tissues and cell lines [3,7]. Western blotting with specific antibodies can confirm protein expression and post-translational modifications.
CRISPR-based functional genomics
CRISPR knockout, point mutation, knock-in, and overexpression models allow precise manipulation of AKR1C genes to study their roles in chlordecone metabolism and disease [6,7,8]. These models can be combined with high-throughput screening to identify genetic modifiers.
Structural biology
X-ray crystallography and cryo-EM can determine the three-dimensional structure of chlordecone reductase and its complexes with substrates and inhibitors, providing insights into catalytic mechanism and substrate specificity.
How CRISPR Can Be Used to Study GO:0047743 chlordecone reductase activity
Knockout
CRISPR knockout of AKR1C1 or AKR1C2 in human liver cell lines (e.g., HepG2) can abolish chlordecone reductase activity, allowing researchers to assess its contribution to chlordecone detoxification and steroid metabolism. Knockout models also help identify compensatory pathways.
Point Mutation
Introducing point mutations in the catalytic residues of AKR1C1 (e.g., Tyr55) via CRISPR knock-in can reveal the importance of specific amino acids for chlordecone reductase activity and substrate specificity. Such models are valuable for understanding enzyme mechanism and for testing structure-based inhibitors.
Knock-in
Knock-in of epitope tags (e.g., FLAG, HA) into the endogenous AKR1C1 locus enables studies of protein localization, interaction, and turnover without overexpression artifacts. Knock-in of human AKR1C variants into mouse models can model human genetic diversity in chlordecone metabolism.
Overexpression
CRISPR-mediated overexpression of AKR1C3 or AKR1C2 in cancer cell lines can mimic the elevated enzyme levels seen in tumors, facilitating studies on drug resistance and hormone-dependent proliferation. Overexpression models are also useful for screening inhibitors.
How EDITGENE Supports chlordecone reductase activity Research
Researchers studying chlordecone reductase activity-related genes often need to determine whether a candidate gene is causally involved in chlordecone metabolism, hormone signaling, or drug resistance. EDITGENE provides a comprehensive suite of CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of GO:0047743 and its associated genes.
Contact EDITGENE today to design your custom CRISPR model for chlordecone reductase activity research.
Frequently Asked Questions About chlordecone reductase activity
What is chlordecone reductase activity?
Chlordecone reductase activity (GO:0047743) is the catalysis of the reaction: chlordecone alcohol + NADP+ = chlordecone + H+ + NADPH. It is an oxidoreductase that detoxifies chlordecone by converting its alcohol metabolite back to the parent ketone.
What genes are involved in chlordecone reductase activity?
The primary genes are AKR1C1 and AKR1C2, which encode aldo-keto reductases with chlordecone reductase activity. Other AKR family members may also contribute [4,7].
Which enzyme catalyzes chlordecone reductase activity?
The enzyme is a cytosolic aldo-keto reductase, originally purified from human liver as a 37 kDa monomer. It is also known as CDR or chlordecone-alcohol:NADP+ 2-oxidoreductase.
What is the reaction catalyzed by chlordecone reductase?
The enzyme catalyzes the NADP+-dependent oxidation of chlordecone alcohol to chlordecone, producing NADPH and a proton.
Where is chlordecone reductase expressed?
It is expressed in human liver and other tissues, with mRNA detected in liver, kidney, and gastrointestinal tract [3,7].
How can I measure chlordecone reductase activity?
Activity can be measured spectrophotometrically by monitoring NADPH formation at 340 nm or by LC-MS quantification of chlordecone and its alcohol metabolite [1,2].
What diseases are associated with chlordecone reductase?
Chlordecone reductase activity is linked to chlordecone neurotoxicity and hormone-dependent cancers due to its role in steroid metabolism [2,3].
Can CRISPR be used to study chlordecone reductase?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression models enable precise functional studies of AKR1C genes and their role in chlordecone metabolism [6,7,8].
What are the inhibitors of chlordecone reductase?
Inhibitors of aldo-keto reductases, such as flufenamic acid and indomethacin, also inhibit chlordecone reductase activity.
Is chlordecone reductase activity reversible?
Yes, the reaction is reversible, and the direction depends on substrate and product concentrations.
Conclusion
Chlordecone reductase activity (GO:0047743) is a well-defined molecular function that plays a critical role in the metabolism of the organochlorine pesticide chlordecone and in endogenous steroid hormone pathways. The enzyme, an aldo-keto reductase encoded primarily by AKR1C1 and AKR1C2, catalyzes the NADP+-dependent oxidation of chlordecone alcohol to chlordecone. Its activity has implications for chlordecone toxicity, hormone-dependent cancers, and drug resistance. CRISPR-based models offer powerful tools to dissect the physiological and pathological roles of this enzyme, and EDITGENE provides comprehensive services to support such research.
References
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- 2. Molowa DT et al.. 1986. Characterization of a unique aldo-keto reductase responsible for the reduction of chlordecone in the liver of the gerbil and man.. J Toxicol Environ Health 17(4):375-84 PMID: 2420999
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- 4. Deyashiki Y et al.. 1994. Molecular cloning of two human liver 3 alpha-hydroxysteroid/dihydrodiol dehydrogenase isoenzymes that are identical with chlordecone reductase and bile-acid binder.. Biochem J 299 ( Pt 2)(Pt 2):545-52 PMID: 8172617
- 5. O'connor T et al.. 1999. Major differences exist in the function and tissue-specific expression of human aflatoxin B1 aldehyde reductase and the principal human aldo-keto reductase AKR1 family members.. Biochem J 343 Pt 2(Pt 2):487-504 PMID: 10510318
- 6. Cheng KC et al.. 1991. Molecular cloning and expression of rat liver 3 alpha-hydroxysteroid dehydrogenase.. Mol Endocrinol 5(6):823-8 PMID: 1922097
- 7. Shiraishi H et al.. 1998. Sequence of the cDNA of a human dihydrodiol dehydrogenase isoform (AKR1C2) and tissue distribution of its mRNA.. Biochem J 334 ( Pt 2)(Pt 2):399-405 PMID: 9716498
- 8. Lin HK et al.. 1999. Genomic structure of rat 3alpha-hydroxysteroid/dihydrodiol dehydrogenase (3alpha-HSD/DD, AKR1C9).. J Steroid Biochem Mol Biol 71(1-2):29-39 PMID: 10619355
