Domains: Belongs to the HAD-like hydrolase superfamily, characterized by a conserved haloacid dehalogenase (HAD) fold .
Catalytic Motif: Predicted hydrolase activity, though the exact catalytic residues remain uncharacterized .
Expression: Ubiquitous, with notable presence in liver, lung, skeletal muscle, and salivary glands .
Orthologs: Conserved across vertebrates, including Mus musculus, Rattus norvegicus, and Danio rerio .
Methionine Salvage Pathway: Catalyzes the first step in recycling S-methyl-5'-thioadenosine (MTA), a byproduct of polyamine biosynthesis, into methionine .
Substrate Specificity: Binds 6-aminopurine nucleosides (e.g., MTA, adenosine) but exhibits broad substrate tolerance .
HDHD3 interacts with enzymes involved in nucleotide and amino acid metabolism:
Substrate Analysis: HDHD3 hydrolyzes MTA but shows no activity toward non-protein substrates like phospholipids or sugars .
Structural Insights: Recombinant HDHD3 (Q9BSH5) has been purified for in vitro assays, confirming hydrolase activity .
Disease Associations: Limited data, but interactions with mitochondrial proteins (e.g., PITRM1) suggest potential links to neurodegenerative disorders .
Mechanistic Details: The exact catalytic mechanism and regulatory pathways remain undefined .
Pathological Relevance: No direct disease associations reported, but toxicogenomic databases link it to chemical response pathways .
HDHD3 (haloacid dehalogenase-like hydrolase domain containing 3) is a 251 amino acid protein that belongs to the HAD-like hydrolase superfamily . This family differs structurally from the α/β hydrolase family and includes L-2-haloacid dehalogenase, epoxide hydrolases, and phosphatases .
The HDHD3 gene is located on human chromosome 9q32, a chromosome that comprises approximately 145 million bases (4% of the human genome) and encodes nearly 900 genes . The gene has ID 81932 with synonyms including C9orf158 . It has an ORF size of 756 bp .
Methodological consideration: When designing primers for HDHD3 amplification or detection, researchers should account for potential alternative splicing and ensure specificity by checking primer sequences against genomic databases to avoid amplification of related HAD family members.
HDHD3 has a molecular weight of approximately 28,000 Daltons . Structural data is available through the Protein Data Bank (PDB) under ID 3K1Z , providing atomic-level details that can inform structure-function studies.
As a member of the HAD-like hydrolase superfamily, HDHD3 likely possesses a conserved catalytic core with a Rossmann-like fold featuring catalytic residues positioned to perform hydrolytic reactions. Based on family characteristics, it likely uses an aspartate-based nucleophilic catalysis mechanism.
Methodological consideration: When performing biochemical characterization of HDHD3, researchers should:
Include appropriate buffer conditions (typically pH 7-8)
Test various divalent cations as cofactors (Mg²⁺, Mn²⁺)
Consider substrate specificity based on structural homology to related HAD family members
Employ both targeted and unbiased approaches to identify physiological substrates
Several recombinant systems are available for HDHD3 expression in experimental models:
| Vector Type | Catalog Number | Features | Applications |
|---|---|---|---|
| Adenovirus (human) | ADV-210908 | CMV promoter, optional reporters | Overexpression studies, localization analysis |
| AAV (human) | AAV-210908 | CMV promoter | Long-term expression studies |
| shRNA Adenovirus | shADV-210908 | Targeted knockdown | Loss-of-function studies |
| shRNA AAV | shAAV-210908 | Sustained knockdown | Chronic depletion models |
Control vectors such as Ad-Null (Cat#1240), Ad-GFP (Cat#1060), and Ad-CMV-Null (Cat#1300) should be employed as experimental controls .
Methodological consideration: When using viral vectors for HDHD3 expression, researchers should:
Optimize viral titer to achieve desired expression levels
Validate expression/knockdown efficiency by qPCR and Western blot
Account for potential cellular stress responses to viral infection
Consider cell type-specific differences in transduction efficiency
Although specific substrates for HDHD3 are not explicitly identified in the available literature, researchers can employ several approaches to characterize its enzymatic activity:
Generic hydrolase assays using synthetic substrates common to the HAD superfamily
Phosphatase activity assays using p-nitrophenyl phosphate or similar chromogenic substrates
Mass spectrometry-based approaches to identify specific metabolite substrates
Thermal shift assays to identify ligands that stabilize protein structure
Methodological consideration: When developing activity assays for HDHD3, researchers should consider:
Enzyme concentration and substrate range for kinetic analyses
Potential product inhibition effects
Inclusion of appropriate controls (heat-inactivated enzyme, catalytic mutants)
Validation of purified protein integrity by gel filtration or dynamic light scattering
Understanding the biological function of HDHD3 requires integrative approaches:
Genetic approaches:
CRISPR-Cas9 knockout in relevant cell models
Conditional knockout mouse models if HDHD3 is essential
Rescue experiments with wild-type and catalytic mutants
Metabolomic approaches:
Comparative metabolic profiling of HDHD3-depleted vs. control cells
Stable isotope labeling to track metabolic flux alterations
Targeted analysis of candidate pathways based on preliminary findings
Transcriptomic analysis:
Methodological consideration: When designing genetic perturbation experiments, researchers should verify knockdown/knockout efficiency through multiple methods and consider potential compensatory mechanisms by related family members.
While direct evidence linking HDHD3 to specific diseases is not presented in the available literature, several methodological approaches can explore potential pathological roles:
Expression analysis:
Compare HDHD3 expression between normal and diseased tissues
Correlate expression levels with disease progression or clinical outcomes
Perform immunohistochemistry to evaluate protein levels in patient samples
Functional studies:
Genetic association studies:
Methodological consideration: When examining HDHD3 in cancer contexts, researchers should consider the heterogeneity of tumor samples and potentially stratify analyses according to established molecular classifications like the consensus molecular subtypes (CMS) in colorectal cancer .
Computational methods provide valuable insights into HDHD3 function:
Methodological consideration: When using bioinformatic tools, researchers should:
When facing inconsistent results regarding HDHD3 function:
Systematic documentation:
Create comprehensive tables comparing methodological differences
Note cell types, experimental conditions, and reagents used
Assess statistical power and reproducibility metrics
Validation approaches:
Employ multiple detection methods (antibodies from different sources)
Use genetic approaches (siRNA, CRISPR) alongside pharmacological ones
Collaborate with other laboratories for independent verification
Context-dependent function analysis:
Evaluate whether HDHD3 function varies by cell type or physiological state
Consider post-translational modifications that might alter activity
Assess potential isoform-specific effects
Methodological consideration: Researchers should establish consistent experimental parameters when comparing results across studies, including standardized assay conditions, validated reagents, and appropriate positive and negative controls.
The molecular heterogeneity of colorectal cancer has been extensively characterized through gene expression-based classification systems like the consensus molecular subtypes (CMS) . When investigating HDHD3 in cancer:
Stratification approaches:
Analyze HDHD3 expression across different CMS subtypes
Correlate expression with other molecular features (MSI status, mutations)
Consider intratumoral heterogeneity in tissue analyses
Functional relevance assessment:
Evaluate effects of HDHD3 modulation on cancer hallmarks
Determine whether effects are cell type or context-dependent
Consider potential roles in treatment response or resistance
Translational potential evaluation:
Assess prognostic value of HDHD3 expression in patient cohorts
Investigate potential as a biomarker for therapy selection
Consider as a therapeutic target if functionally relevant
Methodological consideration: Cancer studies should employ multiple cell models representing different molecular subtypes and validate findings in patient-derived samples to ensure clinical relevance .
Several methodological hurdles may affect HDHD3 research:
Protein purification challenges:
Optimization of expression conditions to maximize soluble protein yield
Selection of appropriate tags that don't interfere with activity
Validation of proper folding and oligomeric state
Activity assay limitations:
Uncertain physiological substrates complicating relevance assessment
Potential low catalytic efficiency requiring sensitive detection methods
Distinguishing HDHD3 activity from other cellular phosphatases/hydrolases
Antibody specificity issues:
Cross-reactivity with related HAD family members
Variable performance across applications (Western, IHC, IP)
Batch-to-batch variability affecting reproducibility
Methodological consideration: Researchers should validate commercial antibodies using HDHD3 knockout/knockdown controls and consider generating monoclonal antibodies for critical applications to ensure specificity and reproducibility.
Several cutting-edge approaches may provide new insights into HDHD3 biology:
Proximity labeling methods (BioID, APEX) to identify interaction partners in their native cellular context
CRISPR screens to identify synthetic lethal interactions or genetic dependencies
Single-cell analyses to understand cell-type specific roles and heterogeneity
Cryo-EM studies to complement existing structural data with dynamic information
Methodological consideration: When adopting new technologies, researchers should include appropriate controls and validation steps, while remaining aware of the limitations and potential artifacts associated with each method.
If HDHD3 proves relevant to disease processes, particularly cancer:
Biomarker development:
Evaluate HDHD3 expression or activity as a prognostic indicator
Determine potential value in predicting treatment response
Develop reliable detection methods for clinical implementation
Therapeutic targeting strategies:
Structure-based design of specific inhibitors if disease-promoting
Development of activators if function is protective
Evaluation of synthetic lethal approaches
Integration with molecular classification systems:
The core catalytic domain of the HAD superfamily, including HDHD3, features a three-layered α/β sandwich structure. This structure consists of repetitive β-α units, adopting the topology typical of the Rossmanoid class of α/β fold . The HDHD3 gene is located on chromosome 9 and is involved in hydrolase activity, which is crucial for various biological processes .
HDHD3 plays a significant role in several cellular functions. It is involved in the regulation of protein translocation within mitochondria and abscisic acid-responsive transcription . The gene’s hydrolase activity is essential for maintaining cellular homeostasis and responding to environmental stressors.
Recent studies have highlighted the importance of HDHD3 in various biological contexts. For instance, overexpression of a related HAD superfamily member, OsHAD3, in rice has been shown to affect drought tolerance by altering the accumulation of reactive oxygen species and malondialdehyde . This suggests that HDHD3 and its homologs could be potential targets for genetic engineering to improve stress tolerance in crops.
In the context of human health, HDHD3’s role in hydrolase activity makes it a potential candidate for research into metabolic disorders and other diseases where enzyme regulation is disrupted .