GO:0052885 all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0052885 describes the molecular function that catalyzes the hydrolysis and isomerization of all-trans-retinyl esters to 11-cis-retinol and a fatty acid, a critical step in the visual cycle.
• This activity is essential for regenerating the chromophore 11-cis-retinal, which is required for dim-light vision.
• The enzyme acts as a retinoid isomerohydrolase, coupling ester cleavage with double-bond isomerization in a single reaction.
• Defects in this activity are linked to retinal degeneration and impaired vitamin A metabolism.
• Key proteins include RPE65, which is the primary enzyme responsible for this activity in the retinal pigment epithelium.
• Research methods include knockout and knock-in mouse models, enzymatic assays, and CRISPR-based screens to dissect the pathway.
Description
GO:0052885, all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity, is a molecular function that catalyzes the conversion of all-trans-retinyl esters into 11-cis-retinol and a free fatty acid. This reaction is a cornerstone of the visual cycle, as it generates the precursor for 11-cis-retinal, the chromophore of rhodopsin. The activity is also known as retinoid isomerohydrolase or retinol isomerase, reflecting its dual hydrolase and isomerase nature. Researchers study this term to understand how vitamin A is processed in the eye and liver, and how disruptions lead to diseases such as retinitis pigmentosa and congenital night blindness. The enzymatic step is unique because it couples ester hydrolysis with isomerization, a process that requires specific protein machinery and cofactors. Understanding GO:0052885 is therefore essential for vision science, retinoid biology, and therapeutic development.
all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity At A Glance
| GO ID | GO:0052885 |
|---|---|
| GO term | all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity |
| Ontology | molecular_function |
| Synonym | retinoid isomerohydrolase activity; retinol isomerase activity; all-trans-retinylester 11-cis isomerohydrolase activity |
| Major function | Catalyzes the hydrolysis and isomerization of all-trans-retinyl esters to 11-cis-retinol and fatty acid |
| Reaction | H2O + all-trans-retinyl ester = 11-cis-retinol + fatty acid |
| Related process | Visual cycle, vitamin A metabolism |
| Key enzyme | RPE65 (retinal pigment epithelium-specific 65 kDa protein) |
What Is GO:0052885?
This GO term defines the catalytic activity that hydrolyzes an all-trans-retinyl ester in the presence of water to produce 11-cis-retinol and a fatty acid. It is a molecular function that combines esterase and isomerase activities, enabling the formation of the 11-cis isomer of retinol from the all-trans ester precursor.
Why Is all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity Important in Cell Biology?
GO:0052885 is critical for vision because it produces 11-cis-retinol, which is subsequently oxidized to 11-cis-retinal, the light-sensitive chromophore of rhodopsin. Without this activity, the visual cycle is blocked, leading to impaired dark adaptation and retinal degeneration. The enzyme also plays a role in hepatic vitamin A mobilization, influencing systemic retinoid homeostasis.
• Essential for the regeneration of 11-cis-retinal in the visual cycle.
• Mutations in the enzyme cause Leber congenital amaurosis and retinitis pigmentosa.
• Regulates vitamin A storage and mobilization in the liver.
• Target for therapies aimed at restoring vision in retinal degenerative diseases.
• Provides a model for studying coupled hydrolysis-isomerization reactions.
• Involved in the metabolism of dietary retinoids and their conversion to active forms.
• Its activity can be modulated by inhibitors, offering pharmacological tools.
• Plays a role in the development and function of the retinal pigment epithelium.
What Happens During all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity?
Substrate Binding and Ester Hydrolysis
In simple terms: The enzyme grabs an all-trans-retinyl ester and breaks it apart using water.
The reaction begins with the binding of an all-trans-retinyl ester, such as retinyl palmitate, to the active site of the enzyme. A water molecule then attacks the ester bond, leading to hydrolysis and release of a fatty acid. This step is typical of hydrolases, but in this case, it is coupled to an isomerization event.
Isomerization to 11-cis-Retinol
In simple terms: After breaking the ester, the enzyme flips the molecule into a bent shape called 11-cis.
Following hydrolysis, the enzyme catalyzes the isomerization of the all-trans-retinol intermediate to 11-cis-retinol. This isomerization is unusual because it occurs without a separate isomerase enzyme; the same protein performs both hydrolysis and isomerization. The mechanism likely involves a transient carbocation or radical intermediate, although the exact details are still under investigation.
Product Release and Visual Cycle Continuation
In simple terms: The bent retinol is released and sent to the next step in vision.
The 11-cis-retinol product is released from the enzyme and subsequently oxidized to 11-cis-retinal by retinol dehydrogenases. This retinal then binds to opsin to form rhodopsin, which is essential for phototransduction. The fatty acid byproduct is recycled or used in other metabolic pathways.
Role of Cofactors and Membrane Environment
In simple terms: The enzyme needs a special environment and possibly helper molecules to work.
The activity is membrane-associated, typically in the endoplasmic reticulum of retinal pigment epithelium cells. It may require specific lipids or cofactors for optimal activity, although the exact requirements are not fully defined. The enzyme's conformation and stability are influenced by its lipid environment.
Key Genes Involved in GO:0052885 all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity
The following genes and proteins are directly or indirectly involved in the all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity, based on published literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| RPE65 | Primary enzyme catalyzing the isomerohydrolase reaction | Mutations cause retinal degeneration; target for gene therapy |
| LRAT | Synthesizes all-trans-retinyl esters, the substrate for RPE65 | Knockout models show impaired visual cycle |
| CRALBP | Binds 11-cis-retinol and facilitates its oxidation | Mutations linked to retinal dystrophy |
| RDH5 | Oxidizes 11-cis-retinol to 11-cis-retinal | Defects cause fundus albipunctatus |
| RDH11 | Alternative retinol dehydrogenase | May compensate for RDH5 deficiency |
| ABCA4 | Transports all-trans-retinal and influences retinoid homeostasis | Mutations cause Stargardt disease |
| RGR | Retinal G protein-coupled receptor, may modulate isomerase activity | Potential regulator of the visual cycle |
| BCO1 | Cleaves beta-carotene to retinal, affecting retinoid supply | Polymorphisms influence vitamin A status |
| STRA6 | Transports retinol into cells | Mutations cause Matthew-Wood syndrome |
| TTR | Transports retinol-binding protein and retinol | Amyloidosis affects retinoid delivery |
| RBP4 | Binds and transports retinol in blood | Elevated levels associated with insulin resistance |
| PNPLA4 | Retinyl ester hydrolase in non-ocular tissues | May contribute to hepatic retinoid mobilization |
| CES1 | Carboxylesterase with retinyl ester hydrolase activity | Involved in hepatic vitamin A metabolism |
| CES2 | Carboxylesterase with retinyl ester hydrolase activity | Potential role in intestinal retinoid absorption |
| LPL | Lipoprotein lipase, may affect retinyl ester uptake | Influences systemic retinoid distribution |
| APOB | Apolipoprotein B, component of lipoproteins carrying retinyl esters | Affects retinoid transport |
| APOE | Apolipoprotein E, involved in lipoprotein metabolism | Polymorphisms affect vitamin A levels |
| CYP26A1 | Retinoic acid hydroxylase, affects retinoid signaling | Indirectly influences visual cycle |
How Is all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity Regulated?
The activity of all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity is primarily regulated at the level of enzyme expression and post-translational modifications. RPE65 expression is controlled by transcription factors such as OTX2 and CRX in the retinal pigment epithelium. Additionally, the enzyme's activity can be modulated by its lipid environment and interactions with other visual cycle proteins like CRALBP. Inhibitors of retinyl ester formation can indirectly reduce the substrate availability for this enzyme, thereby affecting its flux.
all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| RPE65 | Leber congenital amaurosis, retinitis pigmentosa | Rpe65 knockout mouse, patient iPSC-derived RPE |
| LRAT | Retinal dystrophy, vitamin A deficiency | Lrat knockout mouse |
| CRALBP | Retinitis pigmentosa, macular dystrophy | Cralbp knockout mouse |
| RDH5 | Fundus albipunctatus | Rdh5 knockout mouse |
| ABCA4 | Stargardt disease | Abca4 knockout mouse |
Retinal Degenerations
Mutations in RPE65, the enzyme responsible for GO:0052885, cause Leber congenital amaurosis type 2 and retinitis pigmentosa, leading to severe vision loss. These mutations impair the isomerohydrolase activity, blocking the visual cycle and causing photoreceptor degeneration.
Vitamin A Deficiency and Night Blindness
Inadequate vitamin A intake or defects in retinyl ester hydrolysis can lead to night blindness and xerophthalmia. The reduced production of 11-cis-retinol directly affects rhodopsin regeneration.
Hepatic Retinoid Storage Disorders
Impaired hydrolysis of retinyl esters in the liver can lead to excessive vitamin A storage or deficiency, contributing to liver fibrosis and metabolic disorders. The enzyme activity is essential for mobilizing vitamin A from hepatic stores.
From all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of RPE65 abolish 11-cis-retinol production? | Rpe65 knockout mouse or CRISPR knockout in RPE cells |
| Can a point mutation in RPE65 alter substrate specificity? | CRISPR point mutation knock-in in cell lines |
| Does overexpression of RPE65 increase visual cycle flux? | Transgenic overexpression in mouse retina |
| How does LRAT deficiency affect substrate availability? | Lrat knockout mouse |
| Can tagged RPE65 be used to track localization? | Knock-in of fluorescent tag at endogenous locus |
| What is the role of CRALBP in 11-cis-retinol handling? | CRISPR knockout of CRALBP in RPE cells |
How to Study the all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| HPLC | Levels of retinoids including 11-cis-retinol | Enzymatic activity assays |
| LC-MS/MS | Retinoid quantification with high sensitivity | Metabolic profiling |
| RNA-seq | Gene expression changes | Transcriptomic analysis of visual cycle genes |
| CRISPR knockout screens | Genes affecting the activity | Functional genomics |
| Western blot | Protein expression and modifications | RPE65 protein levels |
| Immunofluorescence | Subcellular localization | RPE65 trafficking |
| Electroretinography | Retinal function | Mouse models of retinal degeneration |
Enzymatic Activity Assays
Researchers measure the isomerohydrolase activity using retinyl ester substrates and HPLC to detect 11-cis-retinol formation. These assays are typically performed with cell lysates or purified enzyme fractions.
CRISPR Screening
Genome-wide CRISPR knockout screens can identify genes that modify the visual cycle or affect RPE65 activity. Such screens have revealed novel regulators of retinoid metabolism.
Transcriptomics and Proteomics
RNA-seq and mass spectrometry can profile expression changes in visual cycle genes under different conditions. Proteomic analysis of RPE cells can reveal post-translational modifications of RPE65.
Imaging and Localization Studies
Fluorescence microscopy with tagged RPE65 can visualize its subcellular localization in the endoplasmic reticulum. Live-cell imaging can track retinoid transport and metabolism.
How CRISPR Can Be Used to Study GO:0052885 all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity
Knockout
CRISPR knockout of RPE65 or LRAT in cell lines and animal models abolishes the isomerohydrolase activity, providing a clean background to study the visual cycle. These models are used to test gene therapy approaches.
Point Mutation
Introducing disease-associated point mutations in RPE65 via CRISPR can recapitulate human retinal degeneration phenotypes in vitro and in vivo. Such models help dissect the molecular basis of enzyme dysfunction.
Knock-in
Knock-in of fluorescent or affinity tags at the endogenous RPE65 locus allows real-time tracking of the enzyme and its interactions. This approach preserves native regulation.
Overexpression
CRISPR-mediated overexpression of RPE65 or other visual cycle genes can enhance 11-cis-retinol production, useful for studying pathway flux and potential therapies. Overexpression models help identify rate-limiting steps.
How EDITGENE Supports all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity Research
Researchers studying all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity-related genes often need to determine whether a candidate gene is causally involved in the pathway or merely correlated. EDITGENE provides a comprehensive suite of CRISPR services to enable such functional studies with high precision and reproducibility.
Contact EDITGENE today to design your custom CRISPR model for all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity research.
Frequently Asked Questions About all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity
What is GO:0052885?
GO:0052885 is a molecular function term describing the enzyme activity that converts all-trans-retinyl esters to 11-cis-retinol and a fatty acid, a key step in the visual cycle.
What genes are involved in all-trans-retinyl-ester hydrolase, 11-cis retinol forming activity?
The primary gene is RPE65, but other genes such as LRAT, CRALBP, and RDH5 are also involved in the pathway.
What is the role of RPE65 in vision?
RPE65 catalyzes the isomerohydrolase reaction that produces 11-cis-retinol, which is essential for regenerating the visual pigment rhodopsin.
How is this activity measured?
It is typically measured using enzymatic assays with retinyl ester substrates and HPLC or LC-MS/MS to detect 11-cis-retinol formation.
What diseases are associated with defects in this activity?
Mutations in RPE65 cause Leber congenital amaurosis and retinitis pigmentosa, leading to severe vision loss.
Can CRISPR be used to study this activity?
Yes, CRISPR knockout, point mutation, and knock-in models are widely used to dissect the function of RPE65 and related genes.
What are the synonyms for GO:0052885?
Synonyms include retinoid isomerohydrolase activity, retinol isomerase activity, and all-trans-retinylester 11-cis isomerohydrolase activity.
Is this activity present in tissues other than the eye?
Yes, retinyl ester hydrolase activity is also found in the liver and intestine, where it mobilizes vitamin A stores.
What cofactors are required for this activity?
The activity is membrane-associated and may require specific lipids, but no small-molecule cofactor has been definitively identified.
How can I create a knockout model for RPE65?
EDITGENE provides CRISPR knockout services to generate RPE65 knockout cell lines and animal models for functional studies.
Conclusion
GO:0052885 represents a unique molecular function that couples ester hydrolysis with isomerization to produce 11-cis-retinol, a critical step in the visual cycle. Its importance is underscored by its link to retinal degenerative diseases and vitamin A metabolism. Understanding this activity through CRISPR-based models and biochemical assays will continue to shed light on vision science and therapeutic development.
References
- 1. Grumet L et al.. 2016. Hepatic Retinyl Ester Hydrolases and the Mobilization of Retinyl Ester Stores.. Nutrients 9(1) PMID: 28035980
- 2. Trehan A et al.. 1990. Inhibitors of retinyl ester formation also prevent the biosynthesis of 11-cis-retinol.. Biochemistry 29(2):309-12 PMID: 2302381
- 3. Harrison EH. 2000. Lipases and carboxylesterases: possible roles in the hepatic utilization of vitamin A.. J Nutr 130(2S Suppl):340S-344S PMID: 10721902
- 4. Helgerud P et al.. 1982. Acyl CoA:retinol acyltransferase in rat small intestine: its activity and some properties of the enzymic reaction.. J Lipid Res 23(4):609-18 PMID: 7097126
