GO:0102076 beta,beta-carotene-9',10'-cleaving oxygenase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0102076 describes the enzymatic activity that cleaves beta-carotene at the 9',10' double bond, producing 10'-apo-beta-carotenal and beta-ionone [1,5].
• This activity is primarily associated with the enzyme BCO2 (beta,beta-carotene-9',10'-dioxygenase), a member of the carotenoid oxygenase family [1,5].
• BCO2 is evolutionarily distinct from BCO1 (the 15,15'-monooxygenase) and exhibits broader substrate specificity, including xanthophylls [1,6].
• Loss of BCO2 function in humans leads to accumulation of macular carotenoids in the retina, suggesting a protective role in the eye.
• In mice, BCO2 ablation causes hepatic mitochondrial dysfunction, oxidative stress, and hypothalamic metabolic remodeling, linking the enzyme to whole-body metabolism [2,3].
• Studying GO:0102076 requires integrating enzymology, cell models, and CRISPR-based perturbations to dissect its roles in nutrition and disease [1,7].
Description
GO:0102076, beta,beta-carotene-9',10'-cleaving oxygenase activity, is a molecular function defined by the catalytic cleavage of beta-carotene at the 9',10' double bond to yield 10'-apo-beta-carotenal and beta-ionone [1,5]. This reaction is a key step in the asymmetric cleavage of carotenoids, distinct from the central cleavage mediated by BCO1 [1,5]. The enzyme responsible, BCO2, belongs to a family of non-heme iron-dependent oxygenases that use molecular oxygen to cleave double bonds in carotenoids. Understanding this activity is important because it influences carotenoid bioavailability, vitamin A production, and the generation of apocarotenoid signaling molecules [1,4]. Research on GO:0102076 has gained momentum due to its implications in human health, particularly in macular pigment accumulation and metabolic regulation [6,2]. BCO2 is expressed in various tissues, including the retina, liver, and hypothalamus, where it modulates oxidative stress and metabolic pathways [2,3]. Genetic variations in BCO2 have been associated with interindividual differences in carotenoid status, highlighting its nutritional relevance. This article provides a comprehensive overview of GO:0102076, covering its definition, biological significance, molecular mechanism, key genes, disease associations, and experimental approaches. By integrating authoritative QuickGO data with published literature, we aim to support researchers in designing robust studies on carotenoid metabolism and its impact on health.
beta,beta-carotene-9',10'-cleaving oxygenase activity At A Glance
| GO ID | GO:0102076 |
|---|---|
| GO term | beta,beta-carotene-9',10'-cleaving oxygenase activity |
| Ontology | molecular_function |
| Synonym | (none) |
| Major function | Catalyzes the oxidative cleavage of beta-carotene at the 9',10' double bond to form 10'-apo-beta-carotenal and beta-ionone |
| Reaction | beta-carotene + O2 = 10'-apo-beta-carotenal + beta-ionone |
| Enzyme family | Carotenoid oxygenase family (non-heme iron-dependent) |
| Representative enzyme | BCO2 (beta,beta-carotene-9',10'-dioxygenase) |
| Substrates | Beta-carotene and other carotenoids, including xanthophylls |
What Is GO:0102076?
GO:0102076 is defined as the catalysis of the reaction: beta-carotene + O2 = 10'-apo-beta-carotenal + beta-ionone. In other words, it is the enzymatic activity that uses molecular oxygen to cleave the 9',10' double bond of beta-carotene, producing two apocarotenoid products. This activity is distinct from central cleavage (15,15') and is mediated by enzymes such as BCO2 [1,5].
Why Is beta,beta-carotene-9',10'-cleaving oxygenase activity Important in Cell Biology?
GO:0102076 is important because it represents a critical enzymatic step in carotenoid metabolism that influences vitamin A homeostasis, production of apocarotenoid signals, and protection against oxidative stress [1,4]. Dysregulation of this activity has been linked to retinal carotenoid accumulation, mitochondrial dysfunction, and metabolic disorders, making it a target for nutritional and therapeutic research [6,2,3].
• Contributes to the generation of apocarotenoids that can act as signaling molecules.
• Plays a role in carotenoid bioavailability and vitamin A production.
• Protects against oxidative stress in tissues such as liver and retina [2,6].
• Its absence leads to macular pigment accumulation in humans.
• Modulates hypothalamic metabolism and energy balance in mice.
• Genetic variations in BCO2 affect carotenoid status in humans.
• Provides a model for studying non-heme iron oxygenases.
• Potential target for modulating carotenoid-related diseases [1,2].
• Important for understanding evolutionary adaptations in carotenoid metabolism.
• Enables research on apocarotenoid signaling in development and disease.
Molecular Mechanism of beta,beta-carotene-9',10'-cleaving oxygenase activity
Substrate Binding and Specificity
In simple terms: The enzyme grabs beta-carotene and positions it for cleavage.
BCO2, the primary enzyme exhibiting GO:0102076 activity, binds beta-carotene and other carotenoids with a relatively broad specificity compared to BCO1 [1,5]. Structural and computational studies suggest that the substrate-binding pocket accommodates the polyene chain, allowing cleavage at the 9',10' position. This binding is facilitated by hydrophobic interactions and a conserved iron-coordinating center.
Catalytic Cleavage Reaction
In simple terms: Oxygen is used to break the carotenoid at a specific double bond.
The catalytic mechanism involves a non-heme iron center that activates molecular oxygen, leading to the oxidative cleavage of the 9',10' double bond of beta-carotene. This reaction yields 10'-apo-beta-carotenal and beta-ionone as products. The cleavage is asymmetric, distinguishing it from the central cleavage by BCO1 [1,5].
Cofactors and Requirements
In simple terms: The enzyme needs iron and oxygen to work.
GO:0102076 activity requires molecular oxygen and a non-heme ferrous iron cofactor. The iron is coordinated by conserved histidine residues within the enzyme's active site. Reducing agents may be necessary to maintain the iron in its active state, as suggested by studies on related carotenoid oxygenases.
Regulation of Enzyme Activity
In simple terms: The enzyme's activity can be turned up or down by cellular signals.
BCO2 expression and activity are regulated at transcriptional and post-transcriptional levels. In mice, BCO2 ablation leads to altered expression of genes involved in mitochondrial function and oxidative stress, indicating feedback regulation. Additionally, genetic variations in BCO2 influence carotenoid status in humans, suggesting polymorphic regulation. However, specific transcription factors or signaling pathways controlling BCO2 remain to be fully elucidated.
Key Genes Involved in GO:0102076 beta,beta-carotene-9',10'-cleaving oxygenase activity
The following genes and proteins are directly or indirectly involved in beta,beta-carotene-9',10'-cleaving oxygenase activity and its biological context.
| Gene | Major Role | Research Relevance |
|---|---|---|
| BCO2 | Encodes the primary enzyme with beta,beta-carotene-9',10'-cleaving oxygenase activity | Central to studies of carotenoid cleavage, macular pigment, and metabolism [1,6] |
| BCO1 | Encodes the 15,15'-monooxygenase for central cleavage of beta-carotene | Provides contrast to BCO2; important for vitamin A production [1,4] |
| RPE65 | Retinoid isomerohydrolase in the visual cycle | Related to carotenoid metabolism in the eye |
| CD36 | Fatty acid translocase involved in carotenoid uptake | Affects carotenoid bioavailability |
| SR-BI | Scavenger receptor class B type I, facilitates carotenoid absorption | Modulates carotenoid status |
| ABCA1 | Cholesterol transporter implicated in carotenoid efflux | Potential modifier of carotenoid levels |
| APOA1 | Major apolipoprotein in HDL, transports carotenoids | Influences carotenoid distribution |
| APOB | Apolipoprotein B, component of LDL | Carotenoid transport |
| CYP27A1 | Sterol 27-hydroxylase, may affect carotenoid metabolism | Indirect role in lipid metabolism |
| PPARα | Nuclear receptor regulating lipid metabolism | Potential regulator of BCO2 expression |
| PGC-1α | Master regulator of mitochondrial biogenesis | Linked to BCO2-related mitochondrial function |
| NRF2 | Oxidative stress response transcription factor | May be activated upon BCO2 loss |
| TNFα | Pro-inflammatory cytokine | Associated with oxidative stress in BCO2 deficiency |
| IL-6 | Inflammatory cytokine | Potential link to BCO2-related inflammation |
| SOD2 | Mitochondrial superoxide dismutase | Oxidative stress marker in BCO2 KO models |
| CAT | Catalase, antioxidant enzyme | Modulated in BCO2 deficiency |
| GPX1 | Glutathione peroxidase 1 | Antioxidant defense in carotenoid metabolism |
| UCP2 | Mitochondrial uncoupling protein 2 | Energy metabolism in BCO2 KO mice |
How Is beta,beta-carotene-9',10'-cleaving oxygenase activity Regulated?
The activity of beta,beta-carotene-9',10'-cleaving oxygenase is regulated at multiple levels. Transcriptional regulation of BCO2 may involve nuclear receptors such as PPARα, given its role in lipid metabolism. In BCO2 knockout mice, hepatic mitochondrial dysfunction and oxidative stress are accompanied by altered expression of PGC-1α, NRF2, and antioxidant enzymes, suggesting feedback regulation. Furthermore, hypothalamic metabolome remodeling in BCO2-ablated mice indicates systemic metabolic regulation. Genetic polymorphisms in BCO2 also contribute to interindividual variability in carotenoid status, highlighting genetic regulation.
beta,beta-carotene-9',10'-cleaving oxygenase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| BCO2 | Macular pigment accumulation, retinal degeneration | BCO2 KO mice, human retinal pigment epithelial cells |
| BCO2 | Hepatic mitochondrial dysfunction, oxidative stress | Liver-specific BCO2 KO mice |
| BCO2 | Hypothalamic metabolic remodeling, obesity | Hypothalamic BCO2 KO mice |
| BCO1 | Vitamin A deficiency, carotenemia | BCO1 KO mice |
| BCO2 | Cancer (potential via oxidative stress) | BCO2 KO cancer cell lines [1,2] |
BCO2 and Macular Degeneration
In humans, inactivity of BCO2 leads to retinal accumulation of macular carotenoids, which may protect against age-related macular degeneration but also suggests a role in pigmentary retinopathies. The absence of BCO2 activity alters the ratio of carotenoids in the macula, potentially affecting visual function.
Metabolic Disorders and Mitochondrial Dysfunction
BCO2 knockout mice exhibit hepatic mitochondrial dysfunction, increased oxidative stress, and metabolic disorders, including altered hypothalamic metabolome [2,3]. These findings link GO:0102076 activity to energy balance and metabolic syndrome, suggesting that BCO2 may be a therapeutic target for metabolic diseases [2,3].
Cancer and Oxidative Stress
Carotenoids and their cleavage products have been implicated in cancer prevention, partly through antioxidant mechanisms. Loss of BCO2 may increase oxidative stress, a known contributor to carcinogenesis. However, direct evidence linking BCO2 to cancer remains limited and requires further investigation.
From beta,beta-carotene-9',10'-cleaving oxygenase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does BCO2 loss affect carotenoid accumulation? | BCO2 knockout cell lines (e.g., HepG2, ARPE-19) |
| What is the effect of BCO2 on mitochondrial function? | Liver-specific BCO2 knockout mice |
| How does BCO2 regulate hypothalamic metabolism? | Hypothalamic BCO2 knockout mice |
| Can BCO2 activity be modulated by specific mutations? | Point mutation knock-in of BCO2 in cell lines |
| Does BCO2 overexpression alter oxidative stress? | BCO2 overexpression in HEK293 or HepG2 cells |
| What is the impact of BCO2 on apocarotenoid signaling? | Tagged BCO2 knock-in for localization and interaction studies |
How to Study the beta,beta-carotene-9',10'-cleaving oxygenase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| HPLC/LC-MS | Carotenoid and apocarotenoid levels | Enzyme activity assays [1,5] |
| RNA-seq | Transcriptome changes | BCO2 knockout vs wild-type [2,3] |
| qPCR | Specific gene expression | Validation of BCO2 and targets |
| Western blot | Protein abundance | BCO2 protein levels |
| Metabolomics | Global metabolite profiling | Hypothalamic metabolome |
| Fluorescence microscopy | Subcellular localization | Tagged BCO2 imaging |
| CRISPR screening | Gene function in pathways | Identify modifiers of carotenoid metabolism |
Enzymatic Activity Assays
Direct measurement of beta,beta-carotene-9',10'-cleaving oxygenase activity can be performed using HPLC or LC-MS to detect the formation of 10'-apo-beta-carotenal and beta-ionone from beta-carotene [1,5]. These assays require purified enzyme or cell lysates and are essential for validating GO:0102076 in vitro.
Gene Expression Analysis
RNA-seq and qPCR can quantify BCO2 mRNA levels across tissues and conditions, providing insights into transcriptional regulation [2,3]. Such studies have revealed altered expression of metabolic genes in BCO2 knockout models.
Proteomics and Metabolomics
Mass spectrometry-based proteomics and metabolomics can identify changes in protein abundance and metabolite profiles associated with BCO2 activity. Hypothalamic metabolome remodeling in BCO2 KO mice was uncovered using metabolomics.
Imaging and Localization
Fluorescence microscopy with tagged BCO2 can reveal subcellular localization and interactions. This approach helps understand how BCO2 accesses its substrates in lipid droplets or membranes.
How CRISPR Can Be Used to Study GO:0102076 beta,beta-carotene-9',10'-cleaving oxygenase activity
Knockout
CRISPR-Cas9 knockout of BCO2 in cell lines (e.g., HepG2, ARPE-19) or mice enables the study of loss-of-function phenotypes, such as carotenoid accumulation and oxidative stress [2,6]. These models are crucial for establishing causality between GO:0102076 and observed biological effects.
Point Mutation
Introducing point mutations in the catalytic residues of BCO2 (e.g., histidines coordinating iron) can abolish enzymatic activity while preserving protein structure, allowing precise dissection of GO:0102076's contribution to carotenoid metabolism.
Knock-in
Knock-in of tagged BCO2 (e.g., GFP or FLAG) via CRISPR allows visualization and immunoprecipitation of the enzyme, facilitating studies on localization, interaction partners, and dynamics.
Overexpression
CRISPR activation (CRISPRa) or lentiviral overexpression of BCO2 can increase enzymatic activity, enabling gain-of-function studies to assess the impact on carotenoid cleavage, oxidative stress, and metabolic pathways.
How EDITGENE Supports beta,beta-carotene-9',10'-cleaving oxygenase activity Research
Researchers studying beta,beta-carotene-9',10'-cleaving oxygenase activity-related genes often need to determine whether a candidate gene is causally involved in carotenoid metabolism, oxidative stress, or metabolic regulation. EDITGENE provides comprehensive CRISPR-based services to accelerate this discovery process.
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Frequently Asked Questions About beta,beta-carotene-9',10'-cleaving oxygenase activity
What is beta,beta-carotene-9',10'-cleaving oxygenase activity?
It is the enzymatic activity (GO:0102076) that cleaves beta-carotene at the 9',10' double bond to produce 10'-apo-beta-carotenal and beta-ionone [1,5].
What genes are involved in beta,beta-carotene-9',10'-cleaving oxygenase activity?
The primary gene is BCO2, which encodes the enzyme responsible for this activity [1,5].
What is the difference between BCO1 and BCO2?
BCO1 catalyzes central cleavage of beta-carotene at the 15,15' bond, while BCO2 catalyzes eccentric cleavage at the 9',10' bond [1,5].
How is beta,beta-carotene-9',10'-cleaving oxygenase activity measured?
It can be measured using HPLC or LC-MS to detect the formation of 10'-apo-beta-carotenal and beta-ionone from beta-carotene [1,5].
What diseases are associated with BCO2 dysfunction?
BCO2 dysfunction is linked to macular pigment accumulation, hepatic mitochondrial dysfunction, oxidative stress, and metabolic disorders [6,2,3].
Is BCO2 expressed in the retina?
Yes, BCO2 is expressed in the retina, and its inactivity leads to accumulation of macular carotenoids in humans.
Can CRISPR be used to study BCO2 function?
Yes, CRISPR knockout, point mutation, and knock-in models are powerful tools to dissect BCO2 function and its role in carotenoid metabolism [2,6].
What are the products of the BCO2 reaction?
The products are 10'-apo-beta-carotenal and beta-ionone.
Does BCO2 require cofactors?
Yes, BCO2 requires molecular oxygen and a non-heme ferrous iron cofactor for activity.
How does BCO2 affect metabolism?
BCO2 ablation in mice leads to hypothalamic metabolome remodeling and metabolic disorders, indicating a role in energy balance.
Conclusion
GO:0102076, beta,beta-carotene-9',10'-cleaving oxygenase activity, is a key enzymatic function in carotenoid metabolism with significant implications for nutrition, oxidative stress, and metabolic health. The enzyme BCO2 mediates this activity, and its dysfunction has been linked to retinal and metabolic disorders [1,6,2,3]. Continued research using advanced CRISPR models and multi-omics approaches will further elucidate its mechanistic roles and therapeutic potential.
References
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- 2. Wu L et al.. 2017. Lack of β, β-carotene-9', 10'-oxygenase 2 leads to hepatic mitochondrial dysfunction and cellular oxidative stress in mice.. Mol Nutr Food Res 61(5) PMID: 27991717
- 3. Guo X et al.. 2017. Ablation of β,β-carotene-9',10'-oxygenase 2 remodels the hypothalamic metabolome leading to metabolic disorders in mice.. J Nutr Biochem 46:74-82 PMID: 28482236
- 4. Biesalski HK et al.. 2007. Conversion of beta-carotene to retinal pigment.. Vitam Horm 75:117-30 PMID: 17368314
- 5. Wyss A. 2004. Carotene oxygenases: a new family of double bond cleavage enzymes.. J Nutr 134(1):246S-250S PMID: 14704328
- 6. Li B et al.. 2014. Inactivity of human β,β-carotene-9',10'-dioxygenase (BCO2) underlies retinal accumulation of the human macular carotenoid pigment.. Proc Natl Acad Sci U S A 111(28):10173-8 PMID: 24982131
- 7. Borel P. 2012. Genetic variations involved in interindividual variability in carotenoid status.. Mol Nutr Food Res 56(2):228-40 PMID: 21957063
- 8. Martínez A et al.. 2022. A Computer Simulation Insight into the Formation of Apocarotenoids: Study of the Carotenoid Oxygenases BCO1 and BCO2 and Their Interaction with Putative Substrates.. Molecules 27(22) PMID: 36431912
