Recombinant Human GAPDHS Protein: Research Guide & Protocol

Recombinant Human GAPDHS Protein is a testis-specific isoform of glyceraldehyde-3-phosphate dehydrogenase that plays a critical role in sperm energy metabolism and male fertility research.

Product SKU

rp367916

Protein Name

Recombinant Human GAPDHS Protein

Species

Human (Homo sapiens)

Protein Family

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) family

Tissue Specificity

Predominantly expressed in testis and spermatogenic cells

Primary Function

Catalyzes glycolytic conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate in sperm

Protein Background and Biological Function

GAPDHS (Glyceraldehyde-3-Phosphate Dehydrogenase, Spermatogenic) is a testis-specific paralogue of the ubiquitously expressed GAPDH enzyme. Unlike somatic GAPDH, GAPDHS contains an extended N-terminal proline-rich domain that anchors it to the fibrous sheath of the sperm flagellum, making it a structural as well as a metabolic component of mature spermatozoa.

GAPDHS catalyzes the NAD⁺-dependent oxidative phosphorylation of glyceraldehyde-3-phosphate (G3P) to 1,3-bisphosphoglycerate (1,3-BPG), a central step in glycolysis. Because mature sperm rely heavily on glycolysis within the flagellum for ATP production to sustain motility, GAPDHS is considered an essential enzyme for sperm function. Research has demonstrated that disruption of GAPDHS expression or activity leads to impaired sperm motility and male infertility in animal models, highlighting its importance as a target in fertility and contraceptive research.

The Recombinant Human GAPDHS Protein (SKU: rp367916) offered by Aladdin Scientific enables researchers to investigate the enzyme's catalytic mechanism, screen inhibitors, develop antibodies, and conduct structural studies under defined, reproducible conditions.

Recommended Handling and Storage Protocol

Reconstitution: Centrifuge the vial briefly before opening to collect lyophilized material at the bottom. Reconstitute the protein in sterile, ultrapure water or a buffer appropriate for your downstream assay (e.g., phosphate-buffered saline, pH 7.4, supplemented with 0.1% BSA to minimize adsorptive losses). Allow the solution to equilibrate for 10–15 minutes at room temperature with gentle swirling; do not vortex.

Storage: Upon receipt, store lyophilized protein at –20 °C or –80 °C for long-term stability. Once reconstituted, prepare single-use aliquots to avoid repeated freeze-thaw cycles, which can denature the protein and reduce enzymatic activity. Aliquots should be stored at –80 °C and used within the manufacturer's recommended period. Avoid storing the protein at 4 °C for extended durations.

Working Concentration: Optimal working concentrations depend on the specific assay format. Perform a titration experiment to determine the minimum effective concentration for activity assays, ELISA, or Western blot applications.

Note: Specific reconstitution volume, buffer composition, and concentration recommendations should be confirmed against the product datasheet for SKU rp367916.

Key Research Applications

Recombinant Human GAPDHS Protein (rp367916) is suitable for a range of research applications:

• Enzyme Activity Assays: Use as a positive control or study substrate in NADH-coupled spectrophotometric assays measuring G3P oxidation. Absorbance changes at 340 nm are used to track NAD⁺ reduction.
• Inhibitor Screening: The recombinant protein is well-suited for high-throughput and fragment-based screening of small-molecule inhibitors targeting GAPDHS as a male contraceptive or anti-parasitic target.
• Antibody Development and Validation: Use as an immunogen for antibody generation, or as an antigen standard for ELISA and Western blot validation.
• Structural and Biophysical Studies: Suitable for studies including thermal shift assays, isothermal titration calorimetry (ITC), and surface plasmon resonance (SPR) to characterize ligand binding.
• Cell-Free Reconstitution Studies: Investigate protein-protein interactions within the sperm glycolytic enzyme complex.

Quality Considerations and Experimental Tips

Purity Verification: Prior to initiating sensitive assays, verify protein purity by SDS-PAGE. A single band at the expected molecular weight confirms integrity. If degradation bands are observed, the lot should not be used for kinetic studies.

Activity Verification: Confirm enzymatic activity using a standard NADH-coupled assay before use in inhibitor screening campaigns. Inactive or partially active protein will produce unreliable IC50 data.

Endotoxin Levels: For cell-based assays, confirm that endotoxin levels are within acceptable limits (typically <1 EU/µg). Consult the product datasheet for lot-specific endotoxin data.

Reducing Agents: GAPDHS contains active-site cysteine residues critical for catalysis. Ensure the working buffer contains an appropriate reducing agent (e.g., DTT or TCEP) if required, to maintain the active reduced form of the enzyme. However, note that reducing agents may interfere with some downstream assay chemistries.

Protein Concentration Determination: Measure protein concentration by absorbance at 280 nm (A₂₈₀) using the calculated extinction coefficient, or by a colorimetric method such as BCA or Bradford assay, to ensure consistency across experiments.

Frequently asked questions

What is the difference between GAPDHS and GAPDH?

GAPDHS (spermatogenic) is a testis-specific paralogue of the ubiquitous housekeeping enzyme GAPDH. The key structural difference is an extended proline-rich N-terminal domain in GAPDHS that anchors it to the fibrous sheath of the sperm flagellum. While somatic GAPDH is expressed in virtually all tissues and has multiple non-glycolytic moonlighting roles, GAPDHS function is specialized for providing glycolytic ATP to support sperm motility.

How should I store Recombinant Human GAPDHS Protein (rp367916) to maintain activity?

Lyophilized protein should be stored at –20 °C or –80 °C upon receipt. After reconstitution, aliquot the protein into single-use volumes and store at –80 °C to avoid repeated freeze-thaw cycles. Repeated freeze-thawing can significantly reduce enzymatic activity. Always refer to the product datasheet for lot-specific storage recommendations.

Is Recombinant Human GAPDHS Protein suitable for inhibitor screening assays?

Yes, Recombinant Human GAPDHS Protein (rp367916) is suitable for inhibitor screening, including high-throughput screening (HTS) and fragment-based drug discovery approaches. It is recommended to first verify enzymatic activity using a standard NADH-coupled spectrophotometric assay to confirm the protein is fully active before committing to a screening campaign, as partially active protein can compromise IC50 determinations.

Can GAPDHS be used as a loading control in Western blot experiments?

No. Unlike ubiquitous GAPDH, GAPDHS expression is restricted to testis and spermatogenic cells. It is not suitable as a universal loading control. Recombinant Human GAPDHS Protein (rp367916) is best used as an antigen standard or positive control specifically in experiments involving testicular or sperm-related samples.

References

1. Miki K, et al. Targeted disruption of the Akap4 gene causes defects in sperm flagellum and motility. Dev Biol. 2002. [GAPDHS fibrous sheath localization context — general reference; verify applicability]
2. Bone W, et al. Characterization of the testis-specific glyceraldehyde-3-phosphate dehydrogenase isoform (GAPDHS) in spermatogenic cells. [General background reference — verify citation details]
3. Aladdin Scientific. Recombinant Human GAPDHS Protein, SKU rp367916. Product Datasheet. [Cite current version of the product datasheet for lot-specific data]

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.