GO:0033961 cis-stilbene-oxide hydrolase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0033961 cis-stilbene-oxide hydrolase activity is a molecular function that catalyzes the hydrolysis of cis-stilbene oxide to (+)-(1R,2R)-1,2-diphenylethane-1,2-diol.
• The enzyme is a microsomal epoxide hydrolase (mEH) that can be separated from trans-stilbene oxide hydrolase activity, indicating distinct stereochemical preferences.
• Activity varies significantly between species and individuals, with up to several-fold differences in hepatic microsomal epoxide hydrolase activity measured using cis-stilbene oxide as substrate.
• The reaction proceeds with inversion of configuration at the benzylic carbon, as shown by kinetic and stereochemical studies.
• Beyond xenobiotic metabolism, microsomal epoxide hydrolase can hydrolyze endogenous lipids such as 2-arachidonoylglycerol, linking this activity to endocannabinoid signaling.
• Epoxide hydrolases with cis-stilbene oxide hydrolase activity are found in diverse organisms, including plants, fungi, and mammals, and are targets for enzyme engineering.
Description
cis-stilbene-oxide hydrolase activity (GO:0033961) is a molecular function defined as the catalysis of the reaction: cis-stilbene oxide + H2O = (+)-(1R,2R)-1,2-diphenylethane-1,2-diol. This activity is typically associated with microsomal epoxide hydrolase (mEH), an enzyme that plays a central role in the detoxification of epoxide-containing xenobiotics and in the metabolism of endogenous epoxides. The stereochemical outcome of the reaction is highly specific, producing the (1R,2R)-diol from cis-stilbene oxide, which has made this substrate a classic probe for studying epoxide hydrolase stereochemistry. Researchers use cis-stilbene oxide to distinguish between different epoxide hydrolase isoforms and to assess interindividual variability in drug metabolism. The activity is not limited to mammals; soluble epoxide hydrolases from plants and fungi also exhibit cis-stilbene oxide hydrolase activity, suggesting broad biological significance. Recent studies have expanded the known functions of mEH to include the hydrolysis of endogenous signaling lipids such as 2-arachidonoylglycerol, implicating this activity in the regulation of endocannabinoid tone. Understanding GO:0033961 is therefore important for toxicology, pharmacology, and the development of enzyme inhibitors and engineered biocatalysts.
cis-stilbene-oxide hydrolase activity At A Glance
| GO ID | GO:0033961 |
|---|---|
| GO term | cis-stilbene-oxide hydrolase activity |
| Ontology | molecular_function |
| Synonym | microsomal epoxide hydrolase activity; epoxide hydratase activity; arene-oxide hydratase activity; cis-epoxide hydrolase activity |
| Major function | Catalyzes the hydrolysis of cis-stilbene oxide to (+)-(1R,2R)-1,2-diphenylethane-1,2-diol |
| Reaction | cis-stilbene oxide + H2O = (+)-(1R,2R)-1,2-diphenylethane-1,2-diol |
| Cellular location | Microsomal fraction (endoplasmic reticulum) for mEH; also cytosolic forms in some species |
| Substrate specificity | cis-stilbene oxide; also acts on other epoxides including carbamazepine 10,11-epoxide and naphthalene oxide |
| Species distribution | Mammals (human, monkey, rat), plants (Brassica napus), fungi (Alternaria alternata) |
What Is GO:0033961?
In simple terms, GO:0033961 describes the ability of an enzyme to take cis-stilbene oxide, add water, and convert it into a specific diol product, (+)-(1R,2R)-1,2-diphenylethane-1,2-diol. This is a hydrolytic reaction that opens the epoxide ring. The term is a molecular function, meaning it describes what the enzyme does at the chemical level, rather than where it is located or what pathway it belongs to. The official definition from QuickGO is: Catalysis of the reaction: cis-stilbene oxide + H2O = (+)-(1R,2R)-1,2-diphenylethane-1,2-diol. Synonyms include microsomal epoxide hydrolase activity, epoxide hydratase activity, and arene-oxide hydratase activity, reflecting the historical names used for this activity.
Why Is cis-stilbene-oxide hydrolase activity Important in Cell Biology?
GO:0033961 is important because it represents a key detoxification activity that protects cells from reactive epoxides, which can damage DNA and proteins. The enzyme responsible, microsomal epoxide hydrolase, is highly polymorphic in humans, and interindividual differences in activity can influence susceptibility to chemical carcinogens and the metabolism of drugs such as carbamazepine. The stereochemical precision of the reaction makes it a valuable model for understanding enzyme mechanism and for engineering enantioselective biocatalysts. Furthermore, the discovery that mEH can hydrolyze the endocannabinoid 2-arachidonoylglycerol links this activity to lipid signaling and potential therapeutic targets for pain and inflammation. In agriculture and biotechnology, plant and fungal epoxide hydrolases with this activity are studied for their roles in toxin production and stress responses.
• Detoxification of carcinogenic and toxic epoxides, protecting cellular macromolecules from damage.
• Determines the metabolic fate of drugs such as carbamazepine 10,11-epoxide, affecting drug efficacy and toxicity.
• Provides a stereochemical model for studying epoxide hydrolase mechanism and enantioselectivity.
• Interindividual variability in activity may influence cancer susceptibility and drug response.
• Links to endocannabinoid signaling through hydrolysis of 2-arachidonoylglycerol, with implications for pain and inflammation.
• Serves as a target for enzyme engineering to produce enantiopure diols for pharmaceutical synthesis.
• Plays a role in plant defense and fungal toxin production, relevant to agriculture and food safety.
• Cytosolic epoxide hydrolases with overlapping activity contribute to the overall epoxide metabolism network.
What Happens During cis-stilbene-oxide hydrolase activity?
Substrate binding and orientation
In simple terms: The enzyme grabs the cis-stilbene oxide molecule and positions it perfectly for a chemical attack by water.
The catalytic cycle begins with the binding of cis-stilbene oxide to the active site of microsomal epoxide hydrolase. The enzyme's active site is located in a hydrophobic tunnel that accommodates the aromatic rings of the substrate. The epoxide oxygen is oriented toward the catalytic residues, typically an aspartate nucleophile and a histidine general base, which activate a water molecule for nucleophilic attack. The binding is stereospecific, ensuring that the subsequent attack occurs at one of the two benzylic carbons, leading to the observed (1R,2R)-diol product.
Nucleophilic attack and ring opening
In simple terms: A water molecule attacks the epoxide ring, breaking it open and forming a new bond.
Once the substrate is bound, a water molecule is activated by the catalytic histidine residue and attacks the epoxide carbon. This attack opens the three-membered epoxide ring, forming an alkyl-enzyme intermediate in which the aspartate residue is covalently linked to the substrate. The reaction proceeds with inversion of configuration at the attacked carbon, as demonstrated by stereochemical studies using cis-stilbene oxide. The formation of the covalent intermediate is a key step that ensures high stereoselectivity.
Hydrolysis of the enzyme-substrate intermediate
In simple terms: The enzyme releases the final product by adding water to the intermediate.
The alkyl-enzyme intermediate is subsequently hydrolyzed by a water molecule, releasing the final product, (+)-(1R,2R)-1,2-diphenylethane-1,2-diol, and regenerating the free enzyme. This second hydrolysis step also proceeds with inversion of configuration, resulting in overall retention of stereochemistry at the attacked carbon. The reaction is highly efficient, with turnover numbers comparable to other epoxide hydrolases. The product is a vicinal diol that is more water-soluble and less reactive than the parent epoxide, facilitating its excretion or further metabolism.
Substrate specificity and isoform variation
In simple terms: Different forms of the enzyme prefer different substrates, and this can vary between species and individuals.
Microsomal epoxide hydrolase exhibits broad substrate specificity, but the activity toward cis-stilbene oxide can be separated from that toward trans-stilbene oxide, indicating the existence of distinct activities or isoforms. Studies in rhesus monkey liver showed partial separation of cis- and trans-stilbene oxide hydrolase activities, suggesting that different enzymes or active site conformations are involved. Interindividual and interspecies variation in hepatic microsomal epoxide hydrolase activity has been documented using cis-stilbene oxide as a substrate, with up to several-fold differences among human samples. This variability has implications for drug metabolism and chemical toxicity.
Cellular context and endogenous substrates
In simple terms: The enzyme is not just for detoxifying foreign chemicals; it also acts on natural molecules in the body.
While cis-stilbene oxide is a synthetic substrate used for assay purposes, microsomal epoxide hydrolase also hydrolyzes endogenous epoxides. A novel activity of mEH is the metabolism of the endocannabinoid 2-arachidonoylglycerol, converting it to arachidonic acid and glycerol. This activity links GO:0033961 to the regulation of endocannabinoid signaling, which modulates pain, inflammation, and neurotransmission. The enzyme is predominantly located in the endoplasmic reticulum membrane, where it can access both xenobiotic and endogenous lipid substrates.
Key Genes Involved in GO:0033961 cis-stilbene-oxide hydrolase activity
The following genes and proteins are directly associated with cis-stilbene-oxide hydrolase activity or have been used to study this function.
| Gene | Major Role | Research Relevance |
|---|---|---|
| EPHX1 | Microsomal epoxide hydrolase; primary enzyme for cis-stilbene oxide hydrolysis | Polymorphisms affect activity and disease risk; target for inhibitor design |
| EPHX2 | Soluble epoxide hydrolase; can hydrolyze cis-stilbene oxide in some species | Role in lipid signaling and inflammation; distinct from mEH |
| EPHX3 | Epoxide hydrolase 3; less characterized | Potential overlapping activity; studied in knockout models |
| EPHX4 | Epoxide hydrolase 4; putative | May contribute to epoxide metabolism; under investigation |
| CYP2C9 | Cytochrome P450; produces epoxide metabolites | Generates substrates for epoxide hydrolases; drug metabolism |
| CYP3A4 | Cytochrome P450; major drug-metabolizing enzyme | Produces epoxides from xenobiotics; interplay with mEH |
| GSTT1 | Glutathione S-transferase; detoxifies epoxides | Competes with epoxide hydrolase for substrates |
| GSTM1 | Glutathione S-transferase; detoxifies epoxides | Genetic deletion affects epoxide detoxification |
| NQO1 | Quinone oxidoreductase; antioxidant | Indirectly related to epoxide stress response |
| BNSEH1 | Brassica napus soluble epoxide hydrolase | Plant homolog with cis-stilbene oxide hydrolase activity |
| Alternaria alternata EH | Fungal epoxide hydrolase | Involved in toxin production; cis-stilbene oxide as substrate |
| ABHD12 | Alpha/beta hydrolase domain-containing protein 12 | Endocannabinoid metabolism; may overlap with mEH |
| MGLL | Monoacylglycerol lipase | Endocannabinoid degradation; related to mEH activity |
| FAAH | Fatty acid amide hydrolase | Endocannabinoid metabolism; functional interplay |
| PTGS2 | Cyclooxygenase-2 | Inflammation; epoxide metabolites affect activity |
| ALOX5 | 5-lipoxygenase | Lipid signaling; epoxides as substrates |
| CYP2J2 | Cytochrome P450; produces epoxyeicosatrienoic acids | Endogenous epoxide substrates for mEH |
| CYP2C8 | Cytochrome P450; produces epoxides | Endogenous and xenobiotic epoxide source |
How Is cis-stilbene-oxide hydrolase activity Regulated?
The activity of cis-stilbene-oxide hydrolase is regulated at multiple levels. Transcriptional regulation of EPHX1 is influenced by genetic polymorphisms, particularly in the promoter region, which can alter enzyme expression levels and activity. Post-translational modifications and membrane environment also affect microsomal epoxide hydrolase activity. Additionally, the enzyme can be inhibited by competitive substrates such as carbamazepine 10,11-epoxide, which competes for the active site. In plants, soluble epoxide hydrolase activity is regulated in response to stress and developmental cues. In fungi, epoxide hydrolase activity may be regulated during toxin production. Overall, the regulation of this activity is complex and involves both genetic and environmental factors.
cis-stilbene-oxide hydrolase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| EPHX1 | Cancer susceptibility, drug hypersensitivity | EPHX1 knockout HepG2 cells; patient-derived organoids |
| EPHX1 | Carbamazepine toxicity | CRISPR point mutation knock-in of EPHX1 variants in iPSC-derived hepatocytes |
| EPHX2 | Inflammation, hypertension | EPHX2 knockout mice; overexpression in endothelial cells |
| BNSEH1 | Plant stress response | Arabidopsis overexpression lines; CRISPR knockout |
| Alternaria alternata EH | Fungal toxin production | Gene deletion in fungal strains; toxin assays |
Cancer susceptibility and xenobiotic metabolism
Microsomal epoxide hydrolase, the enzyme responsible for cis-stilbene-oxide hydrolase activity, plays a dual role in carcinogen metabolism. It can detoxify reactive epoxides, but in some cases, it can also activate procarcinogens to more reactive intermediates. Interindividual variability in enzyme activity, as measured with cis-stilbene oxide, has been associated with altered susceptibility to cancers related to environmental exposures, such as lung and bladder cancer. Polymorphisms in EPHX1 that reduce activity may lead to decreased detoxification of carcinogenic epoxides, increasing cancer risk.
Drug metabolism and adverse drug reactions
The activity of microsomal epoxide hydrolase is critical for the metabolism of drugs that form epoxide intermediates, such as carbamazepine, phenytoin, and valproic acid. Variability in cis-stilbene oxide hydrolase activity correlates with differences in the handling of these drugs, potentially leading to adverse drug reactions or therapeutic failure. For example, impaired hydrolysis of carbamazepine 10,11-epoxide can lead to accumulation of the toxic epoxide, causing hypersensitivity reactions.
Endocannabinoid signaling and neurological disorders
The discovery that microsomal epoxide hydrolase can hydrolyze 2-arachidonoylglycerol links cis-stilbene-oxide hydrolase activity to the endocannabinoid system. This activity may influence pain perception, mood, and neuroinflammation. Dysregulation of endocannabinoid metabolism has been implicated in neurological disorders such as anxiety, depression, and chronic pain, suggesting that modulators of this activity could have therapeutic potential.
Plant and fungal biology
In plants, soluble epoxide hydrolases with cis-stilbene oxide hydrolase activity are involved in development and stress responses. In fungi, epoxide hydrolase activity has been linked to the production of host-specific toxins, which are important for pathogenicity. Understanding these roles can inform crop protection strategies and food safety.
From cis-stilbene-oxide hydrolase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does EPHX1 knockout reduce cis-stilbene oxide hydrolase activity? | CRISPR knockout in HepG2 or HEK293 cells |
| How do EPHX1 polymorphisms affect enzyme kinetics? | Point mutation knock-in of rs1051740 and rs2234922 in cell lines |
| Can we tag endogenous EPHX1 for live-cell imaging? | Knock-in of fluorescent tag (e.g., GFP) at EPHX1 locus |
| What is the effect of EPHX1 overexpression on drug metabolism? | Overexpression of EPHX1 in hepatocyte-like cells |
| Which genes modulate epoxide hydrolase activity? | CRISPR library screening with cis-stilbene oxide as probe |
| Does mEH hydrolyze endogenous lipids in vivo? | Knockout mouse models with lipidomics profiling |
How to Study the cis-stilbene-oxide hydrolase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| UV spectrophotometric assay | Diol product formation | Kinetic characterization of purified enzyme |
| HPLC or LC-MS | Substrate depletion and product formation | Activity in tissue homogenates and cell lysates |
| Radiometric assay | Hydrolysis of radiolabeled cis-stilbene oxide | Low-activity samples; high sensitivity |
| qRT-PCR | EPHX1 mRNA levels | Gene expression analysis |
| Western blot | EPHX1 protein levels | Protein quantification |
| Genotyping | EPHX1 polymorphisms | Association studies with disease or drug response |
| CRISPR knockout | Loss of enzyme activity | Causal link between gene and activity |
| Molecular dynamics | Substrate binding and catalysis | Mechanistic insights and enzyme design |
Enzyme activity assays
The most direct method to measure cis-stilbene-oxide hydrolase activity is a spectrophotometric or chromatographic assay using cis-stilbene oxide as substrate. The formation of the diol product can be monitored by UV absorbance or by HPLC/mass spectrometry. These assays are used to determine kinetic parameters (Km, Vmax) and to assess inhibitor potency. Radiometric assays with labeled cis-stilbene oxide provide high sensitivity for low-activity samples.
Genetic and expression analysis
Quantitative PCR and Western blotting are used to measure EPHX1 mRNA and protein levels, respectively. Genotyping of common polymorphisms (e.g., rs1051740, rs2234922) helps correlate genotype with activity. RNA-seq can reveal alternative splicing and expression changes in response to xenobiotics. CRISPR knockout or knockdown with siRNA can establish causality between EPHX1 and observed activity.
Proteomics and interactomics
Mass spectrometry-based proteomics can identify proteins associated with microsomal fractions and quantify EPHX1 abundance. Affinity purification coupled with mass spectrometry can reveal interacting partners. These approaches help place cis-stilbene-oxide hydrolase activity within cellular networks.
Structural and computational studies
X-ray crystallography and homology modeling provide insights into the active site architecture and substrate binding. Molecular dynamics simulations can explore the reaction mechanism and enantioselectivity. Computational design has been used to engineer epoxide hydrolases with altered substrate specificity, including activity toward cis-stilbene oxide.
How CRISPR Can Be Used to Study GO:0033961 cis-stilbene-oxide hydrolase activity
Knockout
CRISPR-Cas9 knockout of EPHX1 in cell lines such as HepG2 or HEK293 abolishes cis-stilbene-oxide hydrolase activity, providing a clean background to study the contribution of this enzyme to epoxide metabolism. Knockout cells can be used to test the specificity of inhibitors and to identify compensatory pathways. In vivo knockout mouse models are valuable for studying the role of mEH in drug metabolism and toxicity.
Point Mutation
Knock-in of specific EPHX1 polymorphisms (e.g., rs1051740, rs2234922) using CRISPR homology-directed repair allows researchers to study how these variants affect enzyme activity, stability, and substrate specificity. Point mutation models can reveal the molecular basis of interindividual variability in cis-stilbene oxide hydrolysis and its impact on drug response.
Knock-in
Knock-in of a fluorescent tag (e.g., GFP) or an epitope tag at the endogenous EPHX1 locus enables live-cell imaging and proteomic analysis of the enzyme. Tagged knock-in models preserve endogenous regulatory elements, providing physiological expression levels. These models are useful for studying subcellular localization and trafficking of microsomal epoxide hydrolase.
Overexpression
Overexpression of EPHX1 or other epoxide hydrolases in mammalian cells or bacteria allows for high-level production of the enzyme for biochemical and structural studies. Overexpression models can also be used to screen for inhibitors or to assess the metabolic capacity of cells toward epoxides. In plants, overexpression of BNSEH1 can enhance stress tolerance.
How EDITGENE Supports cis-stilbene-oxide hydrolase activity Research
Researchers studying cis-stilbene-oxide hydrolase activity-related genes often need to determine whether a candidate gene is causally involved in epoxide metabolism, drug response, or disease susceptibility. EDITGENE provides comprehensive CRISPR gene editing services to create precisely engineered cell models that answer these questions.
Contact EDITGENE today to design your custom CRISPR model for cis-stilbene-oxide hydrolase activity research.
Frequently Asked Questions About cis-stilbene-oxide hydrolase activity
What is cis-stilbene-oxide hydrolase activity?
It is a molecular function (GO:0033961) that catalyzes the hydrolysis of cis-stilbene oxide to (+)-(1R,2R)-1,2-diphenylethane-1,2-diol, typically associated with microsomal epoxide hydrolase.
What genes are involved in cis-stilbene-oxide hydrolase activity?
The primary gene is EPHX1, which encodes microsomal epoxide hydrolase. Other genes such as EPHX2, EPHX3, and EPHX4 may also contribute to related activities.
What is the reaction catalyzed by GO:0033961?
The reaction is: cis-stilbene oxide + H2O = (+)-(1R,2R)-1,2-diphenylethane-1,2-diol.
How is cis-stilbene-oxide hydrolase activity measured?
It is commonly measured using spectrophotometric or chromatographic assays that monitor the formation of the diol product from cis-stilbene oxide.
What is the difference between cis- and trans-stilbene oxide hydrolase activity?
They can be separated biochemically, indicating distinct enzyme activities or isoforms with different stereochemical preferences.
Is cis-stilbene-oxide hydrolase activity found in plants?
Yes, soluble epoxide hydrolases from plants such as Brassica napus exhibit this activity.
What diseases are associated with EPHX1 and this activity?
EPHX1 polymorphisms and altered activity have been linked to cancer susceptibility and adverse drug reactions, such as carbamazepine hypersensitivity.
Can CRISPR be used to study cis-stilbene-oxide hydrolase activity?
Yes, CRISPR knockout, point mutation knock-in, and overexpression models are powerful tools to study the function of EPHX1 and related genes.
What are the synonyms for cis-stilbene-oxide hydrolase activity?
Synonyms include microsomal epoxide hydrolase activity, epoxide hydratase activity, arene-oxide hydratase activity, and cis-epoxide hydrolase activity.
Does microsomal epoxide hydrolase have endogenous substrates?
Yes, it can hydrolyze endogenous lipids such as 2-arachidonoylglycerol, linking this activity to endocannabinoid signaling.
Conclusion
cis-stilbene-oxide hydrolase activity (GO:0033961) is a well-defined molecular function with broad significance in xenobiotic detoxification, drug metabolism, and endogenous lipid signaling. The enzyme responsible, microsomal epoxide hydrolase, is subject to interindividual variability and is implicated in cancer susceptibility and adverse drug reactions. Advanced CRISPR models and biochemical assays continue to unravel the mechanistic details and therapeutic potential of this activity. EDITGENE provides the tools and expertise to accelerate research in this field.
References
- 1. Moody DE et al.. 1987. Purification of microsomal epoxide hydrolase from liver of rhesus monkey: partial separation of cis- and trans-stilbene oxide hydrolase.. Arch Biochem Biophys 258(1):156-66 PMID: 3310896
- 2. Kitteringham NR et al.. 1996. Interindividual and interspecies variation in hepatic microsomal epoxide hydrolase activity: studies with cis-stilbene oxide, carbamazepine 10, 11-epoxide and naphthalene.. J Pharmacol Exp Ther 278(3):1018-27 PMID: 8819481
- 3. Bellucci G et al.. 1994. Kinetics and stereochemistry of the microsomal epoxide hydrolase-catalyzed hydrolysis of cis-stilbene oxides.. Chirality 6(7):577-82 PMID: 7986671
- 4. Bellevik S et al.. 2002. Brassica napus soluble epoxide hydrolase (BNSEH1).. Eur J Biochem 269(21):5295-302 PMID: 12392563
- 5. Schladt L et al.. 1988. Human liver cytosolic epoxide hydrolases.. Eur J Biochem 176(3):715-23 PMID: 3169021
- 6. Nithipatikom K et al.. 2014. A novel activity of microsomal epoxide hydrolase: metabolism of the endocannabinoid 2-arachidonoylglycerol.. J Lipid Res 55(10):2093-102 PMID: 24958911
- 7. Pinot F et al.. 1997. Characterization of epoxide hydrolase activity in Alternaria alternata f. sp. lycopersici. Possible involvement in toxin production.. Mycopathologia 140(1):51-8 PMID: 9608724
- 8. Arabnejad H et al.. 2020. Computational Design of Enantiocomplementary Epoxide Hydrolases for Asymmetric Synthesis of Aliphatic and Aromatic Diols.. Chembiochem 21(13):1893-1904 PMID: 31961471
