GO:0008803 bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0008803 describes the symmetrical hydrolysis of diadenosine tetraphosphate (Ap4A) into two ADP molecules and two protons.
• The enzyme is a symmetrical pyrophosphohydrolase that cleaves the central pyrophosphate bond of Ap4A, distinguishing it from asymmetrical hydrolases.
• In Escherichia coli, the gene encoding this activity (apaH) is located immediately clockwise to folA and forms an operon with ksgA.
• The E. coli enzyme requires divalent metal ions, particularly Mn2+, for catalytic activity.
• Homologs have been characterized in Drosophila embryos, where the activity is developmentally regulated, and in the firefly Photinus pyralis, where it is abundant in lanterns.
• The enzyme is a target for understanding dinucleotide polyphosphate metabolism and has been studied with chiral phosphorothioate analogues of Ap4A.
Description
GO:0008803, bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity, is a molecular function defined by the catalysis of the reaction P(1),P(4)-bis(5'-adenosyl) tetraphosphate + H2O = 2 ADP + 2 H+. This activity is also known as diadenosine tetraphosphate hydrolase or Ap4A hydrolase, and it specifically cleaves the central pyrophosphate bond of diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) in a symmetrical manner, yielding two ADP molecules. The enzyme belongs to the family of Nudix hydrolases in many organisms, although the E. coli enzyme was initially characterized as a distinct symmetrical pyrophosphohydrolase. Researchers study this activity because Ap4A is a signaling molecule implicated in cellular stress responses, and its hydrolysis is critical for maintaining dinucleotide polyphosphate homeostasis. The E. coli gene encoding this activity, apaH, is located adjacent to folA and forms an operon with ksgA, linking it to folate metabolism and ribosomal RNA modification. Homologs have been identified in eukaryotes, including Drosophila melanogaster, where the enzyme is developmentally regulated, and in the firefly Photinus pyralis, where it is highly abundant in lanterns. The metal requirements of a related enzyme from Bartonella bacilliformis have been studied in detail, revealing a role for Mn2+ in catalysis. Understanding GO:0008803 is therefore essential for dissecting the biological roles of Ap4A and related dinucleotides in both prokaryotes and eukaryotes.
bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity At A Glance
| GO ID | GO:0008803 |
|---|---|
| GO term | bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity |
| Ontology | molecular_function |
| Synonym | Ap4A hydrolase activity; diadenosine tetraphosphate hydrolase activity; symmetrical diadenosine tetraphosphate hydrolase activity |
| Major function | Hydrolysis of diadenosine tetraphosphate (Ap4A) to two ADP molecules and two protons |
| Reaction | P(1),P(4)-bis(5'-adenosyl) tetraphosphate + H2O = 2 ADP + 2 H+ |
| Cofactor | Divalent metal ions (e.g., Mn2+) |
| Substrate specificity | Bis(5'-nucleosidyl) oligophosphates, with preference for Ap4A |
| Prokaryotic gene | apaH in Escherichia coli |
| Eukaryotic homologs | Characterized in Drosophila melanogaster and Photinus pyralis |
What Is GO:0008803?
GO:0008803 describes the enzymatic activity that catalyzes the symmetrical hydrolysis of P(1),P(4)-bis(5'-adenosyl) tetraphosphate (Ap4A) to produce two molecules of ADP and two protons. This activity is specific for the central pyrophosphate bond of the tetraphosphate chain, in contrast to asymmetrical hydrolases that cleave the molecule at a different position. The reaction requires a divalent metal ion cofactor, with Mn2+ being particularly effective for the E. coli enzyme. The term is synonymous with diadenosine tetraphosphate hydrolase, Ap4A hydrolase, and symmetrical diadenosine tetraphosphate hydrolase, among others.
Why Is bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity Important in Cell Biology?
GO:0008803 is important because it controls the cellular levels of diadenosine tetraphosphate (Ap4A), a dinucleotide polyphosphate that has been implicated in stress responses, DNA replication, and cellular signaling. By hydrolyzing Ap4A to ADP, this enzyme prevents the accumulation of the dinucleotide, which can be toxic at high concentrations. In bacteria, the apaH gene is part of an operon with ksgA, linking Ap4A catabolism to ribosomal RNA modification and folate metabolism. In eukaryotes, the developmental regulation of the enzyme in Drosophila embryos suggests a role in embryogenesis. The abundance of the activity in firefly lanterns indicates specialized metabolic functions in certain tissues. Furthermore, the metal dependence of the enzyme, particularly on Mn2+, makes it a model for studying metalloenzyme mechanisms. Understanding this activity is therefore relevant to microbiology, developmental biology, and enzymology.
• Regulates intracellular Ap4A levels, preventing toxicity from dinucleotide polyphosphate accumulation.
• Linked to folate metabolism and ribosomal RNA modification through the apaH-ksgA operon in E. coli.
• Developmentally regulated in Drosophila embryos, suggesting roles in embryogenesis.
• Highly abundant in firefly lanterns, indicating specialized metabolic roles.
• Requires divalent metal ions, providing a model for metalloenzyme catalysis.
• Target of chiral phosphorothioate analogues for studying enzyme stereochemistry.
• Homolog in Bartonella bacilliformis has been structurally and kinetically characterized.
• Potential target for antibacterial drugs due to its role in bacterial stress responses.
• Involved in maintaining nucleotide homeostasis in both prokaryotes and eukaryotes.
• Provides a tool for studying dinucleotide polyphosphate signaling in cells.
Molecular Mechanism of bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity
Substrate Recognition and Binding
In simple terms: The enzyme grabs onto a molecule called Ap4A, which is made of two ADP molecules joined together.
The symmetrical bis(5'-nucleosyl)-tetraphosphatase specifically binds diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) as its primary substrate. The enzyme recognizes the two adenosine moieties and the central tetraphosphate chain, positioning the molecule for cleavage at the central pyrophosphate bond. Substrate specificity studies using bis(5'-nucleosidyl) oligophosphates have shown that the E. coli enzyme prefers Ap4A but can also hydrolyze other dinucleoside polyphosphates to varying degrees.
Metal Ion Requirement and Cofactor Role
In simple terms: The enzyme needs a metal helper, usually manganese, to work properly.
The catalytic activity of bis(5'-nucleosyl)-tetraphosphatase (symmetrical) is dependent on divalent metal ions. For the E. coli enzyme, Mn2+ is the most effective cofactor, although other divalent cations can support activity to a lesser extent. Magnetic resonance and kinetic studies of a homologous enzyme from Bartonella bacilliformis have elucidated the role of Mn2+ in substrate binding and catalysis, revealing a two-metal-ion mechanism typical of many phosphohydrolases.
Catalytic Cleavage of the Central Pyrophosphate Bond
In simple terms: The enzyme cuts the connection between the two ADP halves, releasing them as separate molecules.
The enzyme catalyzes the hydrolysis of the central pyrophosphate bond of Ap4A, resulting in the symmetrical production of two ADP molecules and two protons. This cleavage is a nucleophilic attack by water, activated by the metal ion cofactor, on the phosphorus atom of the pyrophosphate bond. The reaction proceeds without the formation of a covalent enzyme-substrate intermediate, characteristic of a direct displacement mechanism.
Product Release and Enzyme Turnover
In simple terms: After cutting, the enzyme lets go of the two ADP pieces and is ready to act again.
Following cleavage, the two ADP molecules are released from the active site, allowing the enzyme to catalyze another round of hydrolysis. The reaction is essentially irreversible under physiological conditions due to the large free energy change associated with pyrophosphate bond hydrolysis. The enzyme's turnover rate and affinity for Ap4A have been measured for the E. coli enzyme, providing kinetic parameters for comparative studies.
Inhibition and Stereochemical Specificity
In simple terms: Certain chemical mimics can block the enzyme, helping researchers understand how it works.
Chiral phosphorothioate analogues of Ap4A have been used to probe the stereochemical course of the reaction and to inhibit the enzyme. These analogues can act as competitive inhibitors or alternative substrates, providing insights into the enzyme's active site geometry. The symmetrical nature of the reaction distinguishes it from asymmetrical Ap4A hydrolases, which cleave the molecule at a different position to yield AMP and ATP.
Key Genes Involved in GO:0008803 bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity
The genes encoding bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity have been identified in bacteria and eukaryotes, with the E. coli apaH gene being the most thoroughly characterized.
| Gene | Major Role | Research Relevance |
|---|---|---|
| apaH (E. coli) | Encodes diadenosine tetraphosphate pyrophosphohydrolase | Model for bacterial Ap4A catabolism and operon structure |
| ksgA (E. coli) | 16S rRNA dimethyltransferase, forms operon with apaH | Links Ap4A metabolism to ribosome modification |
| folA (E. coli) | Dihydrofolate reductase, adjacent to apaH | Provides genomic context for apaH regulation |
| Drosophila homolog | Developmentally regulated Ap4A hydrolase | Studying embryogenesis and dinucleotide signaling |
| Photinus pyralis homolog | Abundant Ap4A hydrolase in lanterns | Investigating tissue-specific dinucleotide metabolism |
| Bartonella bacilliformis homolog | Mn2+-dependent diadenosine pyrophosphatase | Metal requirement and kinetic studies |
| Nudix hydrolase family members | Broad specificity for dinucleoside polyphosphates | Comparative enzymology and substrate specificity |
| Human NUDT2 (inferred) | Putative Ap4A hydrolase | Potential role in human disease, but not directly cited in provided references |
| Other bacterial apaH homologs | Conserved Ap4A hydrolases | Antibacterial target exploration |
| Yeast homologs | Dinucleotide polyphosphate metabolism | Eukaryotic model for Ap4A regulation |
| Plant homologs | Stress-responsive Ap4A hydrolases | Role in plant stress signaling |
| Archaeal homologs | Putative Ap4A hydrolases | Evolutionary studies of dinucleotide metabolism |
| Firefly lantern enzyme | High specific activity Ap4A hydrolase | Biochemical characterization |
| Drosophila embryo enzyme | Developmental stage-specific activity | Embryonic development studies |
| E. coli ApaH protein | Symmetrical Ap4A pyrophosphohydrolase | Enzyme mechanism and metal dependence |
| B. bacilliformis enzyme | Mn2+-dependent Ap4A hydrolase | Magnetic resonance and kinetic studies |
How Is bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity Regulated?
The expression of the apaH gene in Escherichia coli is co-regulated with ksgA as part of an operon, linking its transcription to ribosomal RNA modification and folate metabolism. The activity of the enzyme is also regulated at the post-translational level by the availability of divalent metal ions, particularly Mn2+, which is required for catalysis. In Drosophila embryos, the activity of bis(5'-nucleosyl)-tetraphosphatase (symmetrical) is developmentally regulated, with changes in enzyme levels or activity correlating with specific embryonic stages. This suggests that the enzyme's function is tightly controlled during development, possibly to modulate Ap4A levels in response to developmental cues.
bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| apaH (E. coli) | Bacterial stress response and virulence | Knockout in E. coli, infection models |
| B. bacilliformis homolog | Bartonellosis (inferred) | Enzyme inhibition assays, metal-binding studies |
| Drosophila homolog | Developmental defects (inferred) | RNAi knockdown in Drosophila embryos |
| Human NUDT2 (putative) | Cancer and neurological disorders (hypothetical) | CRISPR knockout in human cell lines, not directly cited |
| Firefly homolog | Not applicable (basic biology) | Biochemical characterization |
Cancer and Cell Proliferation
Diadenosine tetraphosphate (Ap4A) has been implicated in cell proliferation and stress responses, and its hydrolysis by bis(5'-nucleosyl)-tetraphosphatase (symmetrical) may influence cancer cell growth. However, direct evidence linking mutations in this enzyme to human cancer is limited in the provided references. Further research using knockout models could clarify whether loss of this activity contributes to tumorigenesis.
Neurodegeneration and Stress Responses
Ap4A accumulates under conditions of oxidative stress, and its hydrolysis by symmetrical Ap4A hydrolases may protect cells from stress-induced damage. In neurons, dysregulation of dinucleotide polyphosphate metabolism has been proposed to contribute to neurodegeneration, but specific studies on GO:0008803 in this context are not available in the cited literature.
Infectious Diseases
The apaH gene is conserved in bacterial pathogens such as Bartonella bacilliformis, and the enzyme's metal dependence has been characterized. Inhibitors of this enzyme could potentially serve as antibacterial agents by disrupting Ap4A homeostasis, but no direct clinical studies are cited here.
From bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| What is the effect of apaH deletion on Ap4A levels? | E. coli knockout (apaH-), Ap4A quantification |
| How does Mn2+ affect catalysis? | Point mutations in metal-binding residues, kinetic assays |
| Does the enzyme localize to specific tissues? | Tagged knock-in in Drosophila, imaging |
| Can overexpression reduce Ap4A toxicity? | Overexpression in E. coli or human cells, stress assays |
| What is the role of the apaH-ksgA operon? | Operon deletion and complementation in E. coli |
| How do chiral inhibitors affect enzyme activity? | In vitro assays with phosphorothioate analogues |
How to Study the bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| HPLC-based activity assay | Hydrolysis of Ap4A to ADP | Enzyme kinetics and inhibitor testing |
| Metal ion titration | Dependence on divalent cations | Cofactor requirement studies |
| Gene knockout (apaH) | Loss of enzyme activity and phenotype | Functional genomics in E. coli |
| Complementation assay | Restoration of activity by wild-type gene | Allele-specific function |
| EPR spectroscopy | Metal coordination geometry | Mechanistic studies |
| Developmental activity profiling | Changes in enzyme activity over time | Drosophila embryogenesis |
| Phosphorothioate analogue assays | Stereochemical course and inhibition | Active site probing |
| Protein purification from lanterns | Enzyme abundance and properties | Firefly biochemistry |
Enzymatic Activity Assays
The activity of bis(5'-nucleosyl)-tetraphosphatase (symmetrical) is typically measured using purified enzyme or cell lysates incubated with Ap4A, followed by separation and quantification of substrates and products by HPLC or thin-layer chromatography. Metal dependence is assessed by adding or chelating divalent cations such as Mn2+.
Genetic Knockout and Complementation
Knockout of the apaH gene in E. coli and subsequent complementation with wild-type or mutant alleles allows researchers to link the gene to the enzymatic activity and to study its physiological roles. This approach can be combined with phenotypic assays such as stress sensitivity or growth rate measurements.
Structural and Biophysical Studies
Magnetic resonance and kinetic studies, such as those performed on the Bartonella bacilliformis enzyme, provide detailed information on metal coordination and catalytic mechanism. These methods include electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) to probe the active site.
Developmental and Tissue-Specific Expression Analysis
In Drosophila, the developmental regulation of the enzyme can be studied by measuring activity in embryos at different stages, using biochemical assays or reporter gene fusions. In firefly lanterns, the abundance of the enzyme can be assessed by protein purification and activity measurements.
How CRISPR Can Be Used to Study GO:0008803 bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity
Knockout
CRISPR knockout of the apaH gene in E. coli or its homologs in eukaryotic cells can abolish bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity, leading to accumulation of Ap4A. This model is useful for studying the physiological consequences of losing the enzyme, such as altered stress responses or growth defects.
Point Mutation
Introducing point mutations in the catalytic residues or metal-binding sites of the enzyme can dissect the mechanism of Ap4A hydrolysis. For example, mutations in the Nudix motif or metal-coordinating residues can reduce or eliminate activity, as shown for related enzymes.
Knock-in
Knock-in of a tagged version of the enzyme (e.g., GFP or FLAG) allows for localization and interaction studies in live cells. This approach can reveal tissue-specific expression patterns, as seen in Drosophila embryos.
Overexpression
Overexpression of the enzyme in bacterial or eukaryotic cells can reduce Ap4A levels and protect against Ap4A-induced toxicity. This strategy is useful for testing whether increased Ap4A hydrolysis affects cell proliferation or stress resistance.
How EDITGENE Supports bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity Research
Researchers studying bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity-related genes often need to determine whether a candidate gene is causally involved in Ap4A metabolism, stress responses, or developmental processes. EDITGENE provides a comprehensive suite of CRISPR-based services to create precisely engineered cell models for such investigations.
Contact EDITGENE today to design your custom CRISPR model for bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity research.
Frequently Asked Questions About bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity
What is bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity?
It is an enzymatic activity that hydrolyzes diadenosine tetraphosphate (Ap4A) into two ADP molecules and two protons, as defined by GO:0008803.
What genes are involved in bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity?
The apaH gene in Escherichia coli encodes this activity, and homologs exist in Drosophila, firefly, and Bartonella species [2, 1, 5, 8].
What is the reaction catalyzed by GO:0008803?
The reaction is P(1),P(4)-bis(5'-adenosyl) tetraphosphate + H2O = 2 ADP + 2 H+.
Does bis(5'-nucleosyl)-tetraphosphatase require metal ions?
Yes, the enzyme requires divalent metal ions such as Mn2+ for catalytic activity.
Where is the apaH gene located in E. coli?
The apaH gene is located immediately clockwise to folA and forms an operon with ksgA.
Is bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity developmentally regulated?
Yes, in Drosophila embryos the activity is developmentally regulated, with changes correlating with embryonic stages.
What is the difference between symmetrical and asymmetrical Ap4A hydrolases?
Symmetrical hydrolases cleave Ap4A at the central pyrophosphate bond to yield two ADP molecules, while asymmetrical hydrolases produce AMP and ATP.
Can bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity be inhibited?
Yes, chiral phosphorothioate analogues of Ap4A can act as inhibitors or alternative substrates, as shown in enzymatic studies.
What is the role of the enzyme in firefly lanterns?
The enzyme is highly abundant in firefly lanterns, suggesting a specialized role in dinucleotide metabolism in this tissue.
How can I study bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity using CRISPR?
CRISPR knockout, point mutation, knock-in, and overexpression models can be generated to study the enzyme's function in cells, as offered by EDITGENE [2, 6, 1, 4].
Conclusion
GO:0008803, bis(5'-nucleosyl)-tetraphosphatase (symmetrical) activity, is a well-defined molecular function that controls the levels of diadenosine tetraphosphate (Ap4A) by hydrolyzing it to two ADP molecules. The enzyme is conserved from bacteria to eukaryotes, with the E. coli apaH gene being a paradigm for understanding its genetics and biochemistry [2, 3]. Its metal dependence, developmental regulation, and tissue-specific abundance highlight its importance in diverse biological contexts [6, 1, 5]. Researchers can leverage CRISPR-based models to further dissect its roles in stress responses, development, and disease, with EDITGENE providing tailored services for such studies.
References
- 1. Vallejo CG et al.. 1989. Diadenosine 5",5"'P1,P4-tetraphosphatase in Drosophila embryos: developmental regulation and characterization.. Int J Biochem 21(11):1223-8 PMID: 2558922
- 2. Mechulam Y et al.. 1985. Molecular cloning of the Escherichia coli gene for diadenosine 5',5'''-P1,P4-tetraphosphate pyrophosphohydrolase.. J Bacteriol 164(1):63-9 PMID: 2995325
- 3. Blanchin-Roland S et al.. 1986. The gene for Escherichia coli diadenosine tetraphosphatase is located immediately clockwise to folA and forms an operon with ksgA.. Mol Gen Genet 205(3):515-22 PMID: 3031429
- 4. Guranowski A et al.. 1983. Catabolism of diadenosine 5',5"'-P1,P4-tetraphosphate in procaryotes. Purification and properties of diadenosine 5',5"'-P1,P4-tetraphosphate (symmetrical) pyrophosphohydrolase from Escherichia coli K12.. J Biol Chem 258(24):14784-9 PMID: 6317672
- 5. McLennan AG et al.. 1995. Lanterns of the firefly Photinus pyralis contain abundant diadenosine 5',5"'-P1,P4-tetraphosphate pyrophosphohydrolase activity.. J Biol Chem 270(8):3706-9 PMID: 7876110
- 6. Plateau P et al.. 1985. Catabolism of bis(5'-nucleosidyl) oligophosphates in Escherichia coli: metal requirements and substrate specificity of homogeneous diadenosine-5',5'''-P1,P4-tetraphosphate pyrophosphohydrolase.. Biochemistry 24(4):914-22 PMID: 2986688
- 7. Lazewska D et al.. 1990. P alpha-chiral phosphorothioate analogues of bis(5'-adenosyl)tetraphosphate (Ap4A); their enzymatic synthesis and degradation.. Nucleic Acids Res 18(20):6083-8 PMID: 2172926
- 8. Conyers GB et al.. 2000. Metal requirements of a diadenosine pyrophosphatase from Bartonella bacilliformis: magnetic resonance and kinetic studies of the role of Mn2+.. Biochemistry 39(9):2347-54 PMID: 10694402
