GO:0016847 1-aminocyclopropane-1-carboxylate synthase activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0016847 defines the enzymatic activity that converts S-adenosyl-L-methionine (SAM) to 1-aminocyclopropane-1-carboxylate (ACC), the direct precursor of ethylene.
• ACC synthase (ACS) is the rate-limiting enzyme in ethylene biosynthesis in higher plants, and its activity is tightly regulated by developmental and environmental cues.
• ACS genes are encoded by multigene families; expression is induced by wounding, auxin, submergence, and low oxygen.
• The catalytic mechanism involves a pyridoxal 5'-phosphate (PLP) cofactor and a ketimine intermediate, as shown by structural studies with inhibitors.
• Random mutagenesis and genome-wide analyses have identified critical residues and regulatory motifs in ACS proteins.
• Dysregulation of ACS activity affects fruit ripening, stress responses, and plant growth, making it a target for agricultural biotechnology.
Description
1-aminocyclopropane-1-carboxylate (ACC) synthase (EC 4.4.1.14) is the key enzyme in the biosynthesis of ethylene, a gaseous plant hormone that regulates fruit ripening, senescence, and stress responses. The enzyme catalyzes the conversion of S-adenosyl-L-methionine (SAM) to ACC, which is subsequently oxidized to ethylene by ACC oxidase. This activity is encoded by the GO term GO:0016847 and is found across higher plants, with multiple isoforms encoded by a multigene family. Because ethylene production is often limited by ACC synthase activity, researchers study this enzyme to understand plant development and to manipulate ethylene-related traits. The enzyme is regulated at transcriptional and post-transcriptional levels by diverse signals including wounding, auxin, submergence, and low oxygen. Structural and mutagenesis studies have provided insights into its catalytic mechanism and inhibitor binding.
1-aminocyclopropane-1-carboxylate synthase activity At A Glance
| GO ID | GO:0016847 |
|---|---|
| GO term | 1-aminocyclopropane-1-carboxylate synthase activity |
| Ontology | molecular_function |
| Synonym | ACC synthase activity; 1-aminocyclopropane-1-carboxylate synthetase activity; S-adenosyl-L-methionine methylthioadenosine-lyase activity |
| Major function | Catalyzes the conversion of S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylate, the precursor of ethylene |
| Cofactor | Pyridoxal 5'-phosphate (PLP) |
| Reaction | S-adenosyl-L-methionine = 1-aminocyclopropane-1-carboxylate + S-methyl-5'-thioadenosine + H+ |
| Pathway | Ethylene biosynthesis |
| Organisms | Higher plants, including Arabidopsis thaliana, tomato, rice, apple, mung bean, quinoa |
What Is GO:0016847?
GO:0016847 describes the catalytic activity of 1-aminocyclopropane-1-carboxylate synthase, which converts S-adenosyl-L-methionine into 1-aminocyclopropane-1-carboxylate, S-methyl-5'-thioadenosine, and a proton. This reaction is the committed step in ethylene biosynthesis, as ACC is the immediate precursor of ethylene. The enzyme requires pyridoxal 5'-phosphate as a cofactor and forms a ketimine intermediate during catalysis.
Why Is 1-aminocyclopropane-1-carboxylate synthase activity Important in Cell Biology?
ACC synthase activity is the rate-limiting step in ethylene biosynthesis, a hormone that controls many aspects of plant growth and development, including fruit ripening, senescence, and responses to biotic and abiotic stress. Because ethylene is economically important in agriculture, understanding and manipulating ACC synthase activity can lead to improved crop shelf life, stress tolerance, and yield. Additionally, ACC synthase serves as a model for PLP-dependent enzymes and for studying gene family evolution and regulation.
• Controls ethylene production, which regulates fruit ripening and senescence.
• Mediates plant responses to wounding and mechanical stress.
• Regulates growth under submergence and low oxygen conditions.
• Is induced by auxin, linking hormone signaling to ethylene synthesis.
• Represents a target for biotechnological improvement of crop shelf life.
• Provides a paradigm for PLP-dependent enzyme mechanisms.
• Gene family members show differential expression and regulation.
• Mutations in ACS genes can alter ethylene production and plant phenotype.
• Involved in stress responses such as flooding and hypoxia.
• Used as a marker for ethylene-related physiological processes.
Molecular Mechanism of 1-aminocyclopropane-1-carboxylate synthase activity
Substrate binding and cofactor requirement
In simple terms: The enzyme uses a helper molecule (PLP) to grab the substrate SAM and start the reaction.
ACC synthase is a pyridoxal 5'-phosphate (PLP)-dependent enzyme. The PLP cofactor is covalently bound to a conserved lysine residue and forms an internal aldimine. Upon binding of the substrate S-adenosyl-L-methionine (SAM), a transaldimination reaction occurs to form an external aldimine, positioning the substrate for catalysis.
Catalytic mechanism and intermediate formation
In simple terms: The enzyme breaks a bond in SAM to produce ACC, releasing byproducts.
The catalytic mechanism involves the formation of a ketimine intermediate, as evidenced by structural studies of apple ACC synthase in complex with the inhibitor L-aminoethoxyvinylglycine (AVG). The reaction proceeds through abstraction of a proton from the alpha-carbon of SAM, followed by elimination of methylthioadenosine (MTA) to form the cyclopropane ring of ACC. The reaction also releases a proton.
Inhibition and regulation by small molecules
In simple terms: Certain chemicals can block the enzyme, which helps researchers study its role.
ACC synthase activity is inhibited by aminoethoxyvinylglycine (AVG), a structural analog of SAM that forms a stable ketimine intermediate with PLP. This inhibitor is widely used to study ethylene biosynthesis. Additionally, the enzyme is regulated by phosphorylation and interaction with other proteins, although these mechanisms are less characterized in all plant species.
Gene family and isoform diversity
In simple terms: Plants have many versions of this enzyme, each tuned for different situations.
ACC synthase is encoded by a multigene family in plants. For example, in quinoa (Chenopodium quinoa), genome-wide identification revealed multiple ACS genes with distinct expression patterns. In Arabidopsis thaliana, specific ACS genes are regulated by lithium and other stimuli. The presence of multiple isoforms allows differential regulation of ethylene production in response to developmental and environmental signals.
Post-transcriptional and post-translational regulation
In simple terms: The amount and activity of the enzyme can be controlled after the gene is turned on.
ACC synthase activity is regulated at multiple levels. Transcript levels of ACS genes are induced by auxin, wounding, and submergence. Additionally, the protein can be phosphorylated, and its stability may be affected by interactions with other proteins. In deepwater rice, submergence and low oxygen enhance ACC synthase activity, partly through increased gene expression.
Key Genes Involved in GO:0016847 1-aminocyclopropane-1-carboxylate synthase activity
The following genes encode ACC synthase enzymes or are closely associated with their regulation in various plant species.
| Gene | Major Role | Research Relevance |
|---|---|---|
| ACS1 (Arabidopsis thaliana) | Encodes ACC synthase; regulated by lithium and other signals | Model for studying ACS gene regulation |
| ACS2 (Arabidopsis thaliana) | ACC synthase isoform involved in ethylene production | Widely used in ethylene research |
| ACS6 (Arabidopsis thaliana) | Stress-induced ACC synthase | Studied for wound and hypoxia responses |
| LeACS2 (Solanum lycopersicum) | ACC synthase in tomato fruit | Key for fruit ripening studies |
| LeACS4 (Solanum lycopersicum) | ACC synthase in tomato fruit | Ripening-related ethylene synthesis |
| OsACS1 (Oryza sativa) | ACC synthase in deepwater rice | Submergence-induced ethylene |
| OsACS5 (Oryza sativa) | ACC synthase in rice | Low oxygen response |
| MdACS1 (Malus domestica) | Apple ACC synthase | Structural studies with inhibitor AVG |
| MdACS3 (Malus domestica) | Apple ACC synthase | Fruit ripening and ethylene |
| VrACS1 (Vigna radiata) | Mung bean ACC synthase | Auxin-induced expression |
| VrACS2 (Vigna radiata) | Mung bean ACC synthase | Auxin regulation |
| CqACS1 (Chenopodium quinoa) | Quinoa ACC synthase | Genome-wide family analysis |
| CqACS2 (Chenopodium quinoa) | Quinoa ACC synthase | Expression profiling |
| CqACS3 (Chenopodium quinoa) | Quinoa ACC synthase | Stress response |
| AtACS7 (Arabidopsis thaliana) | ACC synthase | Mutagenesis studies |
| AtACS9 (Arabidopsis thaliana) | ACC synthase | Random mutagenesis |
| SlACS2 (Solanum lycopersicum) | Tomato ACC synthase | Wound ethylene |
| SlACS4 (Solanum lycopersicum) | Tomato ACC synthase | Ripening |
How Is 1-aminocyclopropane-1-carboxylate synthase activity Regulated?
ACC synthase activity is regulated at transcriptional, post-transcriptional, and post-translational levels. In tomato fruit, wounding induces ACS gene expression and enzyme activity. In Arabidopsis, lithium regulates ACS gene expression. In deepwater rice, submergence and low oxygen enhance ACC synthase activity. Auxin induces ACS mRNA in mung bean hypocotyls and apple shoots. Additionally, the enzyme is subject to feedback regulation by ethylene and may be modulated by phosphorylation. The PLP cofactor is essential for activity, and inhibitors such as AVG block the active site.
1-aminocyclopropane-1-carboxylate synthase activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| LeACS2 | Fruit ripening and postharvest spoilage | Tomato knockout or overexpression lines |
| OsACS1 | Submergence tolerance in rice | Rice knockout or overexpression |
| AtACS7 | Ethylene-related growth phenotypes | Arabidopsis mutants |
| MdACS1 | Apple fruit ripening | Apple transformation or CRISPR |
| VrACS1 | Auxin-induced ethylene in mung bean | Mung bean hairy root transformation |
Ethylene and plant disease resistance
Ethylene, produced via ACC synthase activity, plays a complex role in plant defense against pathogens. While ethylene can promote resistance to some pathogens, it can also enhance susceptibility to others. Modulating ACC synthase activity may alter disease outcomes, but the specific effects depend on the plant-pathogen interaction.
Postharvest fruit spoilage
Excessive ethylene production due to high ACC synthase activity accelerates fruit ripening and senescence, leading to postharvest losses. Inhibiting ACC synthase activity or expression is a strategy to extend shelf life in crops like tomato and apple.
Flooding and hypoxia stress
In deepwater rice, submergence induces ACC synthase activity, leading to increased ethylene production that promotes internode elongation, a survival strategy. This highlights the role of ACC synthase in abiotic stress responses.
From 1-aminocyclopropane-1-carboxylate synthase activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of ACC synthase knockout on ethylene production? | CRISPR knockout in Arabidopsis or tomato |
| How does a specific point mutation affect catalytic activity? | Point mutation knock-in in ACS gene |
| What is the subcellular localization of ACC synthase? | Tagged knock-in with fluorescent protein |
| Does overexpression of ACS increase ethylene and alter phenotype? | Overexpression in transgenic plants |
| Which regulatory elements control ACS expression? | Promoter-reporter knock-in |
| What are the interacting partners of ACC synthase? | Tagged knock-in for immunoprecipitation |
How to Study the 1-aminocyclopropane-1-carboxylate synthase activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Enzyme activity assay | ACC production from SAM | Kinetic studies and inhibitor testing |
| RT-qPCR | ACS mRNA levels | Expression profiling under stress |
| RNA-seq | Transcriptome-wide expression | Gene family analysis |
| X-ray crystallography | Three-dimensional structure | Mechanistic studies |
| Site-directed mutagenesis | Effect of specific residues | Catalytic mechanism |
| Western blot | Protein abundance | Post-transcriptional regulation |
| Ethylene measurement | Ethylene gas production | Physiological relevance |
| CRISPR/Cas9 | Gene knockout or knock-in | Functional studies in planta |
Enzyme activity assays
ACC synthase activity is typically measured by incubating protein extracts with SAM and quantifying ACC production using chemical conversion to ethylene or colorimetric methods. These assays are essential for determining kinetic parameters and inhibitor effects.
Gene expression analysis
Transcript levels of ACS genes are quantified by RT-qPCR or RNA-seq. This reveals tissue-specific and stress-induced expression patterns, as shown in tomato, Arabidopsis, rice, and quinoa.
Structural biology
X-ray crystallography and NMR spectroscopy have been used to solve the structure of ACC synthase, particularly in complex with inhibitors like AVG, revealing the ketimine intermediate and active site architecture.
Mutagenesis and functional genomics
Random and site-directed mutagenesis identify residues critical for catalysis. Genome-wide identification of ACS gene families provides insights into evolution and functional divergence.
How CRISPR Can Be Used to Study GO:0016847 1-aminocyclopropane-1-carboxylate synthase activity
Knockout
CRISPR knockout of specific ACS genes can abolish or reduce ACC synthase activity, leading to decreased ethylene production. This is used to study the role of individual isoforms in development and stress responses.
Point Mutation
Introducing point mutations in the catalytic domain of ACS genes allows researchers to dissect the contribution of specific amino acids to enzyme activity and substrate specificity, as demonstrated by random mutagenesis studies.
Knock-in
Knock-in of tagged versions of ACS genes (e.g., GFP or FLAG) enables visualization of protein localization and interaction studies without altering native regulation.
Overexpression
Overexpression of ACS genes under a strong promoter increases ACC synthase activity and ethylene production, useful for studying downstream effects on fruit ripening and stress tolerance.
How EDITGENE Supports 1-aminocyclopropane-1-carboxylate synthase activity Research
Researchers studying 1-aminocyclopropane-1-carboxylate synthase activity-related genes often need to determine whether a candidate gene is causally involved in ethylene production, stress responses, or developmental processes. EDITGENE provides comprehensive CRISPR-based services to generate precise cell and plant models for such functional studies.
Contact EDITGENE today to design your custom CRISPR model for 1-aminocyclopropane-1-carboxylate synthase activity research.
Frequently Asked Questions About 1-aminocyclopropane-1-carboxylate synthase activity
What is 1-aminocyclopropane-1-carboxylate synthase activity?
It is the enzymatic activity that converts S-adenosyl-L-methionine to 1-aminocyclopropane-1-carboxylate (ACC), the precursor of ethylene, as defined by GO:0016847.
What genes are involved in 1-aminocyclopropane-1-carboxylate synthase activity?
Genes encoding ACC synthase include ACS1, ACS2, ACS6 in Arabidopsis, LeACS2 and LeACS4 in tomato, OsACS1 and OsACS5 in rice, and MdACS1 in apple, among others.
How is ACC synthase activity regulated?
It is regulated transcriptionally by wounding, auxin, submergence, and low oxygen, and post-translationally by phosphorylation and protein interactions.
What is the role of ACC synthase in fruit ripening?
ACC synthase produces ACC, which is converted to ethylene, a hormone that triggers fruit ripening; increased ACS activity accelerates ripening.
Can ACC synthase be inhibited?
Yes, inhibitors such as aminoethoxyvinylglycine (AVG) block the active site by forming a ketimine intermediate with the PLP cofactor.
What is the catalytic mechanism of ACC synthase?
It uses a PLP cofactor to form a ketimine intermediate, then eliminates methylthioadenosine to produce ACC.
Which organisms have ACC synthase?
It is found in higher plants, including Arabidopsis, tomato, rice, apple, mung bean, and quinoa.
How can I study ACC synthase activity in the lab?
Common methods include enzyme activity assays, RT-qPCR, RNA-seq, structural biology, and CRISPR mutagenesis.
What are the synonyms for ACC synthase?
Synonyms include ACC synthase activity, 1-aminocyclopropane-1-carboxylate synthetase activity, and S-adenosyl-L-methionine methylthioadenosine-lyase activity.
Why is ACC synthase important in agriculture?
It controls ethylene production, affecting fruit ripening, shelf life, and stress responses, making it a target for crop improvement.
Conclusion
GO:0016847, 1-aminocyclopropane-1-carboxylate synthase activity, is a central enzymatic activity in ethylene biosynthesis, with critical roles in plant development and stress responses. Its regulation is complex, involving multiple gene family members and diverse signals. Understanding this activity provides insights into plant physiology and offers opportunities for agricultural biotechnology. EDITGENE's CRISPR services can facilitate functional studies of ACS genes in various plant models.
References
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- 2. Kende H et al.. 1981. Wound ethylene and 1-aminocyclopropane-1-carboxylate synthase in ripening tomato fruit.. Planta 151(5):476-81 PMID: 24302114
- 3. Liang X et al.. 1996. Li(+)-regulated 1-aminocyclopropane-1-carboxylate synthase gene expression in Arabidopsis thaliana.. Plant J 10(6):1027-36 PMID: 9011084
- 4. Cohen E et al.. 1987. In vivo 1-aminocyclopropane-1-carboxylate synthase activity in internodes of deepwater rice : enhancement by submergence and low oxygen levels.. Plant Physiol 84(2):282-6 PMID: 16665431
- 5. Capitani G et al.. 2002. Apple 1-aminocyclopropane-1-carboxylate synthase in complex with the inhibitor L-aminoethoxyvinylglycine. Evidence for a ketimine intermediate.. J Biol Chem 277(51):49735-42 PMID: 12228256
- 6. Yin L et al.. 2023. Genome-Wide Identification and Expression Analysis of 1-Aminocyclopropane-1-Carboxylate Synthase (ACS) Gene Family in Chenopodium quinoa.. Plants (Basel) 12(23) PMID: 38068656
- 7. Tarun AS et al.. 1998. Random mutagenesis of 1-aminocyclopropane-1-carboxylate synthase: a key enzyme in ethylene biosynthesis.. Proc Natl Acad Sci U S A 95(17):9796-801 PMID: 9707555
- 8. Kim WT et al.. 1992. Induction of 1-aminocyclopropane-1-carboxylate synthase mRNA by auxin in mung bean hypocotyls and cultured apple shoots.. Plant Physiol 98(2):465-71 PMID: 16668663
