GO:0016119 carotene metabolic process: Carotenoid Biosynthesis Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016119 carotene metabolic process describes the chemical reactions and pathways involving carotenes, which are hydrocarbon carotenoids.
• Carotenes such as beta-carotene and lycopene are essential for photosynthesis, photoprotection, and serve as precursors for apocarotenoid signaling molecules.
• Key enzymes include phytoene synthase (PSY), phytoene desaturase (PDS), zeta-carotene desaturase (ZDS), lycopene beta-cyclase (LCYB), and lycopene epsilon-cyclase (LCYE).
• Disruption of carotene metabolism affects human health, including vitamin A deficiency, cancer risk, and macular degeneration.
• Cyanobacteria and microalgae are valuable models for studying carotene metabolism and biotechnological production.
• CRISPR-based knockout, knock-in, and overexpression models enable functional dissection of carotene metabolic genes in plants, algae, and human cells.
Description
Carotene metabolic process (GO:0016119) is a biological process defined as the chemical reactions and pathways involving carotenes, which are hydrocarbon carotenoids. Carotenes are a subclass of carotenoids that lack oxygen functional groups and include important molecules such as beta-carotene, alpha-carotene, and lycopene. These pigments are synthesized by plants, algae, cyanobacteria, and some fungi, but not by humans, making them essential dietary micronutrients. The process is critical for photosynthesis, where carotenes participate in light harvesting and protect against photooxidative damage. In addition to their structural and photoprotective roles, carotenes serve as precursors for apocarotenoids, which function in retrograde signaling and interspecific communication. Understanding carotene metabolism has broad implications for agriculture, biotechnology, and human health, particularly in the context of vitamin A deficiency and chronic diseases. This article integrates authoritative QuickGO data and verified PubMed literature to provide a research-grade overview of GO:0016119, covering its mechanisms, key genes, disease associations, and experimental models.
carotene metabolic process At A Glance
| GO ID | GO:0016119 |
|---|---|
| GO term | carotene metabolic process |
| Ontology | biological_process |
| Synonym | carotene metabolism |
| Definition | The chemical reactions and pathways involving carotenes, hydrocarbon carotenoids. |
| Major function | Biosynthesis and interconversion of hydrocarbon carotenoids such as beta-carotene and lycopene. |
| Key enzymes | Phytoene synthase, phytoene desaturase, zeta-carotene desaturase, lycopene beta-cyclase, lycopene epsilon-cyclase. |
| Organisms | Plants, algae, cyanobacteria, and some fungi; not synthesized in humans. |
| Related pathways | Carotenoid biosynthesis, apocarotenoid metabolism, vitamin A metabolism. |
What Is GO:0016119?
GO:0016119 carotene metabolic process encompasses the chemical reactions and pathways involving carotenes, which are hydrocarbon carotenoids. This process includes the biosynthesis, modification, and degradation of carotene molecules such as beta-carotene, alpha-carotene, and lycopene. Carotenes are synthesized through the mevalonate pathway and subsequent enzymatic steps that convert phytoene into colored carotenes. The term is a child of carotenoid metabolic process (GO:0016116) and is distinct from xanthophyll metabolism, as carotenes lack oxygen-containing functional groups.
Why Is carotene metabolic process Important in Cell Biology?
Carotene metabolic process is fundamentally important because carotenes are essential for photosynthesis, photoprotection, and human nutrition. Beta-carotene is a major dietary source of vitamin A, and its deficiency remains a leading cause of preventable blindness in children. Moreover, carotenes and their cleavage products, apocarotenoids, act as signaling molecules in plants and influence human health through antioxidant and prooxidant activities. Research on GO:0016119 informs strategies for biofortification, metabolic engineering, and understanding disease mechanisms related to oxidative stress and chronic inflammation.
• Carotenes are indispensable for photosynthesis and protect photosynthetic organisms from photooxidative damage.
• Beta-carotene is a precursor of vitamin A, critical for vision, immunity, and embryonic development.
• Carotene metabolism produces apocarotenoids that serve as signaling molecules in plant development and stress responses.
• Dysregulation of carotene metabolism is linked to cancer, macular degeneration, and skin disorders.
• Cyanobacteria and microalgae are emerging platforms for sustainable carotene production.
• Lycopene, a carotene, has been associated with reduced risk of prostate cancer in epidemiological studies.
• Carotene metabolic genes are targets for crop biofortification to combat micronutrient malnutrition.
• Understanding carotene metabolism aids in the development of antioxidants and prooxidant-based therapies.
• The pathway is evolutionarily conserved and provides insights into plastid evolution and endosymbiosis.
• CRISPR-based editing of carotene metabolic genes enables precise functional studies and strain improvement.
What Happens During carotene metabolic process?
Phytoene Synthesis
In simple terms: The pathway starts by joining two molecules to form phytoene, the first carotene precursor.
The first committed step in carotene biosynthesis is the condensation of two geranylgeranyl diphosphate (GGPP) molecules to form phytoene, catalyzed by phytoene synthase (PSY). This reaction occurs in plastids of plants and algae, and in cyanobacteria. PSY is a rate-limiting enzyme, and its expression is tightly regulated in response to developmental and environmental cues.
Desaturation and Isomerization
In simple terms: Phytoene is converted into more colored carotene molecules through a series of desaturation and isomerization steps.
Phytoene undergoes four desaturation steps catalyzed by phytoene desaturase (PDS) and zeta-carotene desaturase (ZDS) in plants, or by a single enzyme CrtI in bacteria, to produce lycopene. These reactions introduce double bonds, extending the conjugated system and enabling light absorption. Isomerization steps, mediated by carotenoid isomerase (CRTISO), are required for proper configuration.
Cyclization to Alpha- and Beta-Carotene
In simple terms: Lycopene is cyclized at both ends to form beta-carotene or at one end to form alpha-carotene.
Lycopene beta-cyclase (LCYB) catalyzes the formation of beta-carotene by adding beta-rings at both ends of lycopene, while lycopene epsilon-cyclase (LCYE) adds an epsilon-ring, leading to alpha-carotene. The ratio of LCYB to LCYE activity determines the flux toward beta-carotene versus alpha-carotene and downstream xanthophylls. In some algae, such as Bangia fuscopurpurea, a single LCYB enzyme can perform both cyclization steps.
Degradation and Apocarotenoid Formation
In simple terms: Carotenes can be cleaved into smaller signaling molecules called apocarotenoids.
Carotenes are oxidatively cleaved by carotenoid cleavage dioxygenases (CCDs) to produce apocarotenoids, including abscisic acid, strigolactones, and retinal. These apocarotenoids function in plant development, stress responses, and as precursors for vitamin A in animals. The balance between carotene accumulation and cleavage is critical for maintaining metabolic homeostasis.
Regulation by Light and Developmental Signals
In simple terms: Light and plant hormones control how fast carotene metabolism runs.
Carotene biosynthesis is regulated transcriptionally by light-responsive factors such as phytochrome-interacting factors (PIFs) and HY5, and post-translationally by redox state and plastid signals. In cyanobacteria, carotene metabolism is modulated by light intensity and nutrient availability. These regulatory mechanisms ensure appropriate pigment composition for photosynthetic efficiency and photoprotection.
Key Genes Involved in GO:0016119 carotene metabolic process
The following genes and enzymes are central to carotene metabolic process (GO:0016119), based on verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| PSY | Phytoene synthase; catalyzes first committed step | Rate-limiting enzyme; target for biofortification |
| PDS | Phytoene desaturase; desaturates phytoene | Herbicide target; essential for carotene biosynthesis |
| ZDS | Zeta-carotene desaturase; desaturates zeta-carotene | Required for lycopene formation |
| CRTISO | Carotenoid isomerase; isomerizes poly-cis carotenes | Affects carotene composition |
| LCYB | Lycopene beta-cyclase; forms beta-carotene | Key branch-point enzyme |
| LCYE | Lycopene epsilon-cyclase; forms alpha-carotene | Determines alpha/beta-carotene ratio |
| CCD1 | Carotenoid cleavage dioxygenase 1; cleaves carotenes | Produces apocarotenoids |
| CCD4 | Carotenoid cleavage dioxygenase 4; cleaves carotenes | Involved in pigment degradation |
| NCED | Nine-cis-epoxycarotenoid dioxygenase; ABA biosynthesis | Links carotene metabolism to stress signaling |
| BCH | Beta-carotene hydroxylase; converts beta-carotene to zeaxanthin | Affects photoprotection |
| CrtI | Bacterial phytoene desaturase | Model for desaturation mechanism |
| CrtY | Bacterial lycopene beta-cyclase | Cyclization in cyanobacteria |
| OR | Orange protein; regulates carotene accumulation | Post-translational regulator |
| PIF1 | Phytochrome-interacting factor; represses PSY | Light signaling regulator |
| HY5 | Transcription factor; activates carotene genes | Light signaling activator |
| GGPS | Geranylgeranyl diphosphate synthase; provides precursor | Upstream of carotene pathway |
| CrtB | Bacterial phytoene synthase | Biotechnological target |
How Is carotene metabolic process Regulated?
Carotene metabolic process is regulated at multiple levels. Transcriptional regulation involves light-responsive transcription factors such as HY5 and PIFs, which modulate the expression of PSY and other biosynthetic genes. Post-translational regulation includes the OR protein, which interacts with PSY to control its activity and stability. In cyanobacteria, carotene biosynthesis is regulated by light intensity and nutrient availability, with CrtB and CrtI being key control points. Additionally, feedback regulation by apocarotenoids and redox signals ensures metabolic balance.
carotene metabolic process and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| PSY | Vitamin A deficiency; biofortification target | Knockout in rice or maize; overexpression in Arabidopsis |
| LCYB | Cancer risk modulation; carotene composition | Knockout in human cell lines; overexpression in algae |
| CCD1 | Apocarotenoid signaling; cancer and inflammation | Knockout in tomato; overexpression in mammalian cells |
| BCH | Macular degeneration; photoprotection | Knockout in mouse retina; knock-in of human variant |
| OR | Carotene accumulation; obesity-related metabolic stress | Knockout in Arabidopsis; overexpression in cyanobacteria |
Vitamin A Deficiency and Carotene Metabolism
Beta-carotene is a major dietary precursor of vitamin A, and impaired carotene metabolism or absorption can lead to vitamin A deficiency, which causes night blindness, xerophthalmia, and increased susceptibility to infections. Populations relying on plant-based diets are particularly at risk, and biofortification of staple crops with beta-carotene is a key intervention.
Cancer and Carotenoids
Epidemiological studies have linked high intake of carotenoid-rich foods to reduced risk of certain cancers, including prostate and lung cancer. However, carotenoids can also act as prooxidants under high oxygen tension or high doses, potentially increasing cancer risk in smokers. The dual role of carotenes in cancer biology underscores the need for precise experimental models to dissect their mechanisms.
Eye Diseases and Carotenes
Lutein and zeaxanthin, which are xanthophylls derived from carotene metabolism, accumulate in the macula and protect against age-related macular degeneration. Although carotenes themselves are not concentrated in the macula, their metabolic interconversion affects the availability of these protective xanthophylls.
Metabolic Disorders and Carotene Metabolism
Disorders of lipid metabolism can affect carotene absorption and transport, as carotenes are lipophilic and require bile acids and lipoproteins for uptake. Conditions such as cystic fibrosis and cholestasis can lead to carotene malabsorption and deficiency.
From carotene metabolic process-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does PSY knockout abolish carotene biosynthesis? | CRISPR knockout in Arabidopsis or rice |
| Does a point mutation in LCYB alter beta-carotene levels? | CRISPR point mutation in algae or cyanobacteria |
| Can knock-in of a bacterial CrtI gene restore carotene synthesis in non-carotenogenic cells? | CRISPR knock-in in human or yeast cells |
| Does overexpression of CCD1 increase apocarotenoid production? | CRISPR overexpression in tomato or tobacco |
| What is the effect of tagged PSY on protein localization? | Tagged knock-in in plant protoplasts |
| Does knockout of OR increase carotene accumulation? | CRISPR knockout in Arabidopsis |
How to Study the carotene metabolic process Process
| Method | What It Measures | Typical Application |
|---|---|---|
| HPLC | Carotene composition and quantity | Quantifying beta-carotene in engineered strains |
| RNA-seq | Transcript levels of carotene genes | Identifying regulatory networks |
| Immunoblotting | Protein abundance of PSY, LCYB | Validating overexpression or knockout |
| CRISPR knockout | Loss-of-function phenotypes | Testing gene essentiality |
| CRISPR knock-in | Tagged or mutant protein expression | Localization and interaction studies |
| Spectrophotometry | Total carotene content | High-throughput screening |
| Mass spectrometry | Apocarotenoid profiling | Detecting cleavage products |
| Confocal microscopy | Subcellular localization of enzymes | Plastid targeting studies |
Spectrophotometric and HPLC Analysis
Carotene levels are commonly quantified by UV-Vis spectrophotometry and high-performance liquid chromatography (HPLC), which separate and identify individual carotenes based on their absorption spectra and retention times. These methods are essential for assessing the impact of genetic modifications on carotene metabolic process.
Transcriptomics and RNA-seq
RNA sequencing (RNA-seq) enables global profiling of gene expression changes in response to perturbations of carotene metabolism. It is used to identify co-regulated genes and regulatory networks involving PSY, LCYB, and CCDs.
Proteomics and Immunoblotting
Proteomic approaches, including mass spectrometry and immunoblotting, measure protein abundance and post-translational modifications of carotene biosynthetic enzymes. These methods help determine whether changes in carotene levels are due to transcriptional or post-transcriptional regulation.
CRISPR-Based Functional Genomics
CRISPR-Cas9 knockout, point mutation, and knock-in strategies are used to dissect the function of individual genes in carotene metabolism. These approaches allow precise editing of PSY, LCYB, and CCD genes in various organisms, from algae to human cells.
How CRISPR Can Be Used to Study GO:0016119 carotene metabolic process
Knockout
CRISPR knockout of carotene metabolic genes such as PSY, LCYB, or CCD1 results in loss of function, enabling researchers to determine their essentiality and contribution to carotene accumulation. For example, knockout of LCYB in algae abolishes beta-carotene synthesis and redirects flux to lycopene.
Point Mutation
CRISPR point mutation introduces specific amino acid substitutions to study catalytic residues or regulatory phosphorylation sites in carotene enzymes. This approach is valuable for dissecting structure-function relationships without completely abolishing gene function.
Knock-in
CRISPR knock-in allows the insertion of reporter tags, such as GFP, or heterologous genes like bacterial CrtI into a target locus. This enables real-time tracking of enzyme localization and activity, and can be used to engineer novel carotene pathways in non-carotenogenic organisms.
Overexpression
CRISPR activation (CRISPRa) or transgenic overexpression of carotene biosynthetic genes increases flux through the pathway, leading to enhanced carotene production. Overexpression of PSY or LCYB in crops or algae is a common strategy for biofortification and biotechnological production.
How EDITGENE Supports carotene metabolic process Research
Researchers studying carotene metabolic process-related genes often need to determine whether a candidate gene is causally involved in carotene biosynthesis, degradation, or signaling. EDITGENE provides comprehensive CRISPR-based services to generate precise cell and organism models for functional validation.
Contact EDITGENE today to design your custom CRISPR model for carotene metabolic process research.
Frequently Asked Questions About carotene metabolic process
What is carotene metabolic process GO:0016119?
GO:0016119 is a Gene Ontology biological process term defined as the chemical reactions and pathways involving carotenes, which are hydrocarbon carotenoids.
What genes are involved in carotene metabolic process?
Key genes include PSY, PDS, ZDS, CRTISO, LCYB, LCYE, CCD1, CCD4, and NCED, among others.
Why is carotene metabolism important for human health?
Carotenes like beta-carotene are precursors of vitamin A, and their metabolism affects vision, immunity, and risk of chronic diseases.
How is carotene metabolic process regulated?
It is regulated transcriptionally by light-responsive factors like HY5 and PIFs, and post-translationally by OR protein and redox signals.
What diseases are associated with carotene metabolism?
Vitamin A deficiency, cancer, macular degeneration, and metabolic disorders have been linked to altered carotene metabolism.
How can CRISPR be used to study carotene metabolism?
CRISPR knockout, point mutation, knock-in, and overexpression enable precise functional analysis of carotene genes in various organisms.
What are apocarotenoids and how do they relate to carotene metabolism?
Apocarotenoids are cleavage products of carotenes that act as signaling molecules in plants and as vitamin A precursors in animals.
Which organisms are used to study carotene metabolic process?
Plants, algae, cyanobacteria, and some fungi are common models, as they naturally synthesize carotenes.
What methods are used to measure carotene levels?
HPLC, spectrophotometry, and mass spectrometry are standard methods for quantifying carotenes and their derivatives.
Can carotene metabolism be engineered for biofortification?
Yes, overexpression or knock-in of biosynthetic genes such as PSY and LCYB can enhance carotene content in crops.
Conclusion
GO:0016119 carotene metabolic process is a fundamental biological pathway with far-reaching implications for photosynthesis, human nutrition, and disease. The integration of QuickGO definitions with verified literature highlights the key enzymes, regulatory mechanisms, and experimental models that drive current research. Advances in CRISPR-based genome editing are accelerating the functional dissection of carotene metabolic genes, offering new opportunities for biofortification, metabolic engineering, and therapeutic development. Continued research on this pathway will deepen our understanding of carotenoid biology and its applications in medicine and agriculture.
References
- 1. Biesalski HK et al.. 2008. Nutritargeting.. Adv Food Nutr Res 54:179-217 PMID: 18291307
- 2. Xu P et al.. 2020. Photosynthesis without β-carotene.. Elife 9 PMID: 32975516
- 3. Henríquez V et al.. 2016. Carotenoids in Microalgae.. Subcell Biochem 79:219-37 PMID: 27485224
- 4. van den Berg H. 1999. Carotenoid interactions.. Nutr Rev 57(1):1-10 PMID: 10047699
- 5. Moreno JC et al.. 2021. Plant apocarotenoids: from retrograde signaling to interspecific communication.. Plant J 105(2):351-375 PMID: 33258195
- 6. Cao TJ et al.. 2017. Cloning and Functional Characterization of a Lycopene β-Cyclase from Macrophytic Red Alga Bangia fuscopurpurea.. Mar Drugs 15(4) PMID: 28398223
- 7. Lowe GM et al.. 2003. Carotenoids as prooxidants?. Mol Aspects Med 24(6):363-9 PMID: 14585307
- 8. Pagels F et al.. 2021. Carotenoids from Cyanobacteria: Biotechnological Potential and Optimization Strategies.. Biomolecules 11(5) PMID: 34063485
