GO:0004463 leukotriene-A4 hydrolase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0004463 (leukotriene-A4 hydrolase activity) catalyzes the hydrolysis of leukotriene A4 (LTA4) to leukotriene B4 (LTB4), a potent pro-inflammatory lipid mediator.
• The enzyme is a bifunctional zinc metallopeptidase: it carries an epoxide hydrolase activity (LTA4 to LTB4) and an aminopeptidase activity that can be pharmacologically separated.
• LTA4H is expressed in myeloid cells including neutrophils, monocytes, and eosinophils, and its activation drives LTB4 production in severe asthma.
• LTA4H has been linked to psoriasis pathogenesis, age-related cognitive decline, and hepatocellular carcinoma progression, making it a multi-disease target.
• Small-molecule LTA4H inhibitors, including photoswitchable and diaryl ether modulators, are actively developed to selectively tune hydrolase versus aminopeptidase functions.
• CRISPR knockout, point-mutation, knock-in, and overexpression models are essential to dissect LTA4H catalytic and non-catalytic roles in inflammation and cancer.
Description
Leukotriene-A4 hydrolase activity (GO:0004463) is a molecular function defined as the catalysis of the reaction H2O + leukotriene A4 = leukotriene B4. This enzymatic step is the terminal and rate-limiting conversion in the LTB4 biosynthetic pathway, producing one of the most potent neutrophil chemoattractants and pro-inflammatory mediators in mammals. Because LTB4 is centrally involved in innate immune responses, the enzyme that generates it has become a focal point for research on inflammatory diseases, cancer, and neurological disorders. The protein product, LTA4H, is a soluble, zinc-dependent metalloenzyme with a unique bifunctional architecture that also exhibits aminopeptidase activity, a feature that has complicated but also enriched drug discovery efforts. Understanding GO:0004463 therefore requires integrating enzymology, cell biology, and disease genetics, and it has direct implications for therapeutic targeting of leukotriene-driven pathology. In this article, we synthesize authoritative QuickGO annotation and verified PubMed literature to provide a research-grade overview of the term, its genes, mechanisms, disease links, and the CRISPR-based models used to study it.
leukotriene-A4 hydrolase activity At A Glance
| GO ID | GO:0004463 |
|---|---|
| GO term | leukotriene-A4 hydrolase activity |
| Ontology | molecular_function |
| Synonym | LTA4H; LTA4 hydrolase activity; leukotriene A(4) hydrolase activity; (7E,9E,11Z,14Z)-(5S,6S)-5,6-epoxyicosa-7,9,11,14-tetraenoate hydrolase activity |
| Definition | Catalysis of the reaction: H2O + leukotriene A(4) = leukotriene B(4). |
| Major function | Conversion of leukotriene A4 to leukotriene B4, a potent pro-inflammatory mediator. |
| Enzyme class | Zinc-dependent metallopeptidase with epoxide hydrolase and aminopeptidase activities. |
| Key substrate | Leukotriene A4 (LTA4). |
| Key product | Leukotriene B4 (LTB4). |
| Primary gene | LTA4H. |
What Is GO:0004463?
In our own words, GO:0004463 describes the catalytic activity of an enzyme that uses water to open the epoxide ring of leukotriene A4, converting it into leukotriene B4. This is a hydrolytic reaction that belongs to the epoxide hydrolase class, and it is the defining biochemical function of the LTA4H protein. The term is a molecular_function in the Gene Ontology and is synonymous with LTA4 hydrolase activity and leukotriene A(4) hydrolase activity.
Why Is leukotriene-A4 hydrolase activity Important in Cell Biology?
GO:0004463 is important because it represents the committed step in the biosynthesis of leukotriene B4, a lipid mediator that amplifies neutrophil recruitment and inflammatory signaling in asthma, psoriasis, and other chronic inflammatory conditions. Beyond inflammation, LTA4H activity has been implicated in age-related cognitive decline through modulation of synaptic function, and in hepatocellular carcinoma progression via the HNRNPA1/LTBP1/TGF-β axis. The enzyme's bifunctional nature, combining epoxide hydrolase and aminopeptidase activities, makes it a challenging but attractive drug target, and selective inhibitors are being developed to dissect these functions. Consequently, researchers across immunology, neuroscience, and oncology need robust models to study GO:0004463 and its downstream effects.
• Central to leukotriene B4 biosynthesis, a key driver of neutrophil chemotaxis and inflammation.
• Validated drug target in severe asthma, where eosinophil LTA4H activation correlates with disease severity.
• Implicated in psoriasis pathogenesis through increased LTA4H activity in lesional skin.
• Modulation of LTA4H activity improves age-related cognitive decline in preclinical models.
• LTA4H overexpression suppresses hepatocellular carcinoma progression via the HNRNPA1/LTBP1/TGF-β axis.
• Bifunctional enzyme with separable hydrolase and aminopeptidase activities, enabling selective pharmacological targeting.
• Subject of structure-based inhibitor design, including photoswitchable compounds for optical control.
• Provides a paradigm for studying lipid mediator enzymes in innate immunity and cancer.
What Happens During leukotriene-A4 hydrolase activity?
Substrate binding and epoxide ring opening
In simple terms: The enzyme grabs leukotriene A4 and uses water to break open a reactive ring, turning it into leukotriene B4.
Leukotriene A4 hydrolase binds its substrate LTA4, a labile epoxide intermediate generated from arachidonic acid by 5-lipoxygenase and LTA4 synthase. The catalytic zinc ion in the active site polarizes a water molecule, which attacks the epoxide ring of LTA4, leading to ring opening and formation of the dihydroxy product LTB4. This reaction is highly stereospecific and constitutes the terminal step in LTB4 biosynthesis.
Bifunctional aminopeptidase activity
In simple terms: The same enzyme can also clip small peptides, which is a second job that can be controlled separately from its LTB4-making job.
In addition to its epoxide hydrolase activity, LTA4H possesses an aminopeptidase activity that cleaves N-terminal amino acids from short peptides, and this activity shares the same active site but can be selectively inhibited. The physiological relevance of the aminopeptidase function is still under investigation, but it has been targeted by diaryl ether modulators to separate it from the pro-inflammatory hydrolase activity. This bifunctionality is a key consideration in drug design and in interpreting knockout phenotypes.
Cellular context and LTB4 production
In simple terms: Immune cells like neutrophils and eosinophils use this enzyme to release LTB4, which calls more immune cells to the site of inflammation.
LTA4H is expressed in myeloid cells, and its activity is particularly prominent in neutrophils, monocytes, and eosinophils. In severe asthma, eosinophils show increased LTA4H activation and LTB4 production, linking the enzyme to airway inflammation. The enzyme is cytosolic but can associate with membranes or be secreted under certain conditions, allowing LTB4 to act locally on surrounding cells.
Regulation by inhibitors and post-translational mechanisms
In simple terms: The enzyme's activity can be turned up or down by drugs and by cellular signals, which is important for controlling inflammation.
LTA4H activity can be inhibited by small molecules that chelate the catalytic zinc or block substrate access, and such inhibitors are being developed for inflammatory diseases. Photoswitchable inhibitors allow optical control of LTA4H activity, providing a tool to study its acute roles in cells and tissues. Additionally, the enzyme may be regulated by phosphorylation or other post-translational modifications, though these mechanisms are less well defined.
Key Genes Involved in GO:0004463 leukotriene-A4 hydrolase activity
The following genes and proteins are directly or indirectly involved in leukotriene-A4 hydrolase activity and its biological context, based on verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| LTA4H | Encodes the bifunctional enzyme with epoxide hydrolase and aminopeptidase activities | Core gene for GO:0004463; target for KO, point mutation, and inhibitor studies |
| ALOX5 | 5-lipoxygenase, upstream enzyme that initiates leukotriene synthesis | Provides substrate LTA4 for LTA4H; often co-studied in inflammation models |
| ALOX5AP | 5-lipoxygenase activating protein, required for ALOX5 activity | Upstream regulator of LTA4 production; potential modifier in asthma |
| LTC4S | Leukotriene C4 synthase, competes with LTA4H for LTA4 | Determines metabolic fate of LTA4; relevant in asthma and allergy |
| LTB4R1 | Receptor for LTB4, mediates chemotaxis | Downstream effector of LTA4H activity; target for functional studies |
| LTB4R2 | Second receptor for LTB4, modulates inflammatory responses | Alternative signaling route for LTB4; studied in KO models |
| HNRNPA1 | RNA-binding protein involved in LTA4H-mediated HCC suppression | Mediates LTA4H effects on TGF-β axis in liver cancer |
| LTBP1 | Latent TGF-β binding protein 1, downstream of LTA4H in HCC | Links LTA4H to TGF-β signaling in tumor microenvironment |
| TGFB1 | Transforming growth factor beta 1, effector in HCC progression | Downstream cytokine modulated by LTA4H axis |
| IL5 | Cytokine driving eosinophil development, relevant to asthma | Context for eosinophil LTA4H activation in severe asthma |
| TNF | Pro-inflammatory cytokine that can induce LTA4H expression | Links inflammation to LTA4H upregulation |
| IL1B | Interleukin-1 beta, pro-inflammatory mediator | Often co-regulated with LTA4H in inflammatory settings |
| CXCL8 | Neutrophil chemoattractant, downstream of LTB4 | Readout for LTA4H activity in neutrophil recruitment |
| SP1 | Transcription factor potentially regulating LTA4H promoter | Candidate for transcriptional control of LTA4H |
| Nfkb1 | NF-kB subunit, drives inflammatory gene expression | Upstream regulator of LTA4H in inflammation |
How Is leukotriene-A4 hydrolase activity Regulated?
LTA4H activity is regulated at multiple levels. Transcriptionally, inflammatory stimuli such as TNF and IL-1β can induce LTA4H expression in myeloid cells. Post-translationally, the enzyme's activity can be modulated by phosphorylation, though specific sites are not fully defined. Pharmacologically, small-molecule inhibitors that chelate the catalytic zinc or block the active site can rapidly suppress LTB4 production, and photoswitchable inhibitors allow reversible, light-dependent control. The aminopeptidase activity can be selectively targeted by diaryl ether modulators, providing a means to separate the two functions. In disease contexts, LTA4H activity is elevated in psoriatic lesions and in eosinophils from severe asthma patients, suggesting disease-specific regulatory mechanisms.
leukotriene-A4 hydrolase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| LTA4H | Psoriasis | Keratinocyte-specific LTA4H knockout or overexpression in mice; human skin equivalents |
| LTA4H | Severe asthma | Eosinophil-specific LTA4H knockout mice; human eosinophil cultures |
| LTA4H | Hepatocellular carcinoma | Liver-specific LTA4H overexpression or knockout; HCC cell lines with CRISPR KO |
| LTA4H | Age-related cognitive decline | Neuron-specific LTA4H knockout or overexpression; aged mice with inhibitor treatment |
| LTA4H | Inflammatory pain and arthritis | Myeloid-specific LTA4H knockout mice; adjuvant-induced arthritis models |
LTA4H in inflammatory skin disease: psoriasis
Psoriasis is a chronic inflammatory skin disease characterized by hyperproliferation of keratinocytes and infiltration of neutrophils and T cells. LTA4H activity is significantly increased in psoriatic lesions compared to normal skin, and this correlates with elevated LTB4 levels, a potent neutrophil chemoattractant. The enzyme is therefore considered a pathogenic contributor to psoriasis, and its inhibition is a potential therapeutic strategy. Experimental models include keratinocyte-specific LTA4H overexpression or knockout in mice, as well as human skin equivalents treated with LTA4H inhibitors.
LTA4H in severe asthma
Severe asthma is often characterized by eosinophilic inflammation that is resistant to corticosteroids. Eosinophils from severe asthma patients show increased LTA4H activation and produce more LTB4, which may amplify airway neutrophilia and inflammation. This links GO:0004463 directly to asthma pathobiology and suggests that LTA4H inhibitors could benefit a subset of severe asthma patients. Research models include eosinophil-specific LTA4H knockout mice and human eosinophil cultures treated with inhibitors.
LTA4H in hepatocellular carcinoma
Recent evidence indicates that LTA4H can suppress hepatocellular carcinoma (HCC) progression by targeting the HNRNPA1/LTBP1/TGF-β axis. In this context, LTA4H overexpression improves the tumor microenvironment and inhibits HCC growth, revealing a tumor-suppressive role that contrasts with its pro-inflammatory functions. This dual role highlights the need for context-specific models, such as liver-specific LTA4H knockout or overexpression in mice, and HCC cell lines with CRISPR-mediated LTA4H knockout.
LTA4H in age-related cognitive decline
LTA4H inhibition improves age-related cognitive decline in mice by modulating synaptic function, independent of its classical inflammatory role. This suggests that LTA4H activity affects neuronal function, possibly through LTB4-mediated neuroinflammation or direct effects on synaptic plasticity. Experimental models include aged mice treated with LTA4H inhibitors and neuron-specific LTA4H knockout or overexpression.
From leukotriene-A4 hydrolase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does LTA4H catalytic activity drive LTB4 production in vivo? | LTA4H knockout mice or CRISPR KO cell lines |
| What is the role of the aminopeptidase activity separate from epoxide hydrolase? | Point mutation of catalytic residues (e.g., zinc-binding) in LTA4H |
| How does LTA4H overexpression affect tumor progression? | Knock-in or overexpression of LTA4H in HCC cell lines and mouse models |
| Can LTA4H be optically controlled in cells? | Knock-in of LTA4H with photoswitchable inhibitor treatment |
| What are the downstream effectors of LTA4H in neurons? | Neuron-specific LTA4H knockout or overexpression in mice |
| How does LTA4H inhibition affect eosinophil function? | CRISPR KO of LTA4H in human eosinophil-like cell lines |
How to Study the leukotriene-A4 hydrolase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS/MS | LTA4 to LTB4 conversion | Enzyme kinetics and inhibitor testing |
| Fluorogenic peptide assay | Aminopeptidase activity | Separating bifunctional activities |
| CRISPR knockout screen | Genes affecting LTB4 production | Pathway discovery |
| RNA-seq | Transcriptional changes | Downstream effects of LTA4H manipulation |
| Proteomics | Protein expression and modifications | Identifying LTA4H interaction partners |
| Live-cell imaging | Real-time LTA4H activity | Photoswitchable inhibitor studies |
| Neutrophil chemotaxis assay | Functional LTB4 output | Inflammation models |
| Immunohistochemistry | LTA4H tissue expression | Psoriasis and asthma biopsies |
Enzymatic activity assays
LTA4H activity can be measured using purified enzyme or cell lysates by monitoring the conversion of LTA4 to LTB4 via reverse-phase HPLC or LC-MS/MS. These assays are essential for validating inhibitors and for characterizing mutant enzymes generated by CRISPR. Aminopeptidase activity can be measured separately using fluorogenic peptide substrates.
CRISPR-based genetic screens
Genome-wide CRISPR knockout screens can identify genes that modulate LTA4H expression or LTB4 production, revealing pathways that regulate GO:0004463. Such screens are particularly useful for uncovering synthetic lethal interactions in cancer cells with LTA4H mutations.
Transcriptomics and proteomics
RNA-seq and proteomics can quantify LTA4H expression and identify downstream transcriptional changes upon LTA4H knockout or overexpression. In HCC, LTA4H overexpression alters the HNRNPA1/LTBP1/TGF-β axis, which can be monitored by phosphoproteomics and cytokine arrays.
Imaging and functional assays
Live-cell imaging with fluorescent LTB4 sensors or photoswitchable inhibitors can visualize LTA4H activity in real time. Neutrophil chemotaxis assays measure the functional consequence of LTB4 production downstream of LTA4H.
How CRISPR Can Be Used to Study GO:0004463 leukotriene-A4 hydrolase activity
Knockout
CRISPR knockout of LTA4H eliminates both epoxide hydrolase and aminopeptidase activities, providing a clean background to study the loss of GO:0004463. LTA4H knockout mice or cell lines show reduced LTB4 production and impaired neutrophil recruitment, validating the enzyme's role in inflammation. In HCC models, LTA4H knockout can accelerate tumor growth, consistent with its tumor-suppressive role.
Point Mutation
Point mutations in the catalytic zinc-binding residues of LTA4H can selectively abolish epoxide hydrolase activity while preserving aminopeptidase activity, or vice versa. Such mutants are invaluable for dissecting the contribution of each activity to disease phenotypes and for validating inhibitor specificity.
Knock-in
Knock-in of tagged LTA4H (e.g., FLAG or GFP) allows for affinity purification and live-cell imaging of the enzyme. Knock-in of disease-associated variants or photoswitchable domains can reveal how structural changes affect catalytic efficiency and subcellular localization.
Overexpression
Overexpression of LTA4H in cell lines or transgenic mice can model the elevated enzyme activity seen in psoriasis and asthma. In HCC, LTA4H overexpression suppresses tumor progression via the HNRNPA1/LTBP1/TGF-β axis, providing a gain-of-function model.
How EDITGENE Supports leukotriene-A4 hydrolase activity Research
Researchers studying leukotriene-A4 hydrolase activity-related genes often need to determine whether a candidate gene is causally involved in LTB4 production, inflammation, or cancer progression. EDITGENE provides a comprehensive suite of CRISPR services to generate precisely engineered cell models that answer these questions.
Contact EDITGENE today to design your custom CRISPR model for leukotriene-A4 hydrolase activity research.
Frequently Asked Questions About leukotriene-A4 hydrolase activity
What is leukotriene-A4 hydrolase activity?
It is the enzymatic activity defined by GO:0004463 that converts leukotriene A4 to leukotriene B4, a potent inflammatory mediator.
What genes are involved in leukotriene-A4 hydrolase activity?
The primary gene is LTA4H, which encodes the bifunctional enzyme; upstream genes include ALOX5 and ALOX5AP, and downstream receptors include LTB4R1 and LTB4R2.
What diseases are associated with LTA4H?
LTA4H has been linked to psoriasis, severe asthma, hepatocellular carcinoma, and age-related cognitive decline.
How is LTA4H activity measured?
It is typically measured by LC-MS/MS quantification of LTB4 production from LTA4, or by fluorogenic aminopeptidase assays.
Can LTA4H be inhibited selectively?
Yes, small-molecule inhibitors can selectively target the epoxide hydrolase or aminopeptidase activity, and photoswitchable inhibitors allow optical control.
What is the role of LTA4H in cancer?
In hepatocellular carcinoma, LTA4H overexpression suppresses tumor progression via the HNRNPA1/LTBP1/TGF-β axis.
How does LTA4H affect the brain?
Inhibition of LTA4H improves age-related cognitive decline in mice by modulating synaptic function.
What CRISPR models are available for LTA4H?
Knockout, point mutation, knock-in, and overexpression models can be generated in cell lines and mice to study GO:0004463.
Is LTA4H a drug target for asthma?
Yes, eosinophil LTA4H activation is increased in severe asthma, and inhibitors are being explored as therapeutics.
What is the difference between LTA4H hydrolase and aminopeptidase activities?
The hydrolase activity produces LTB4, while the aminopeptidase activity cleaves peptides; they share the active site but can be selectively inhibited.
Conclusion
GO:0004463, leukotriene-A4 hydrolase activity, is a central enzymatic function in leukotriene biology, with far-reaching implications for inflammation, cancer, and neuroscience. The bifunctional nature of LTA4H and its role in multiple diseases make it a compelling target for both basic research and therapeutic development. CRISPR-based models, including knockout, point mutation, knock-in, and overexpression, are indispensable for dissecting the precise contributions of this activity in health and disease. As new inhibitors and genetic tools emerge, the field is poised to translate our understanding of GO:0004463 into clinical benefit.
References
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- 2. Yang S et al.. 2025. LTA4H improves the tumor microenvironment and prevents HCC progression via targeting the HNRNPA1/LTBP1/TGF-β axis.. Cell Rep Med 6(3):102000 PMID: 40056904
- 3. Adams JM et al.. 2023. Leukotriene A4 hydrolase inhibition improves age-related cognitive decline via modulation of synaptic function.. Sci Adv 9(46):eadf8764 PMID: 37976357
- 4. Iversen L et al.. 1997. Significance of leukotriene-A4 hydrolase in the pathogenesis of psoriasis.. Skin Pharmacol 10(4):169-77 PMID: 9413890
- 5. Zhou X et al.. 2025. Optical Control of Leukotriene A4 Hydrolase Using Photoswitchable Inhibitors.. J Med Chem 68(20):21520-21533 PMID: 41041960
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- 8. Petruncio G et al.. 2024. Synthesis and Evaluation of diaryl ether modulators of the leukotriene A(4) hydrolase aminopeptidase activity.. Eur J Med Chem 272:116459 PMID: 38704942
