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Ac-VQVD-pNA is an acetylated tetrapeptide chromogenic substrate used in caspase-3 activity studies. The peptide sequence Ac-Val-Gln-Val-Asp is coupled to p-nitroaniline (pNA), providing an absorbance-based readout after proteolytic cleavage.
This defined substrate format is useful for researchers who prefer a straightforward spectrophotometric assay without fluorescence instrumentation.
Product Information
| Property | Specification |
|---|---|
| Product Name | Ac-VQVD-pNA |
| Catalog No. | AS2659 |
| CAS No. | 189684-55-7 |
| Sequence | Ac-Val-Gln-Val-Asp-pNA |
| Sequence Shortening | Ac-VQVD-pNA |
| Peptide Length | 4 amino-acid residues |
| Molecular Formula | C27H39N7O10 |
| Molecular Weight | Approximately 621.64 Da |
| Reporter Group | p-Nitroaniline (pNA) |
| Research Enzyme | Caspase-3 |
| Research Areas | Caspase activity, apoptosis, enzyme kinetics, protease assay development |
Chromogenic Caspase Assay Design
Proteolytic cleavage at the C-terminal Asp–pNA linkage releases free p-nitroaniline. The resulting chromophore can be monitored spectrophotometrically, commonly near 405 nm.
This format allows caspase activity to be followed using a standard absorbance plate reader and is suitable for purified-enzyme experiments, assay optimization and comparative protease studies.
Substrate Recognition
The VQVD sequence has been used as a recognition motif for caspase-3. Peptide substrates, however, should not be interpreted as absolutely enzyme-specific in every biological system because members of the caspase family can have overlapping sequence preferences.
We recommend using appropriate enzyme, inhibitor and background controls when Ac-VQVD-pNA is applied to complex lysates or samples containing multiple active proteases.
Experimental Considerations
Quantitative comparison requires consistent substrate concentration, reaction time, buffer composition and enzyme input. Baseline absorbance from the substrate and sample matrix should also be included in assay design.
Researchers working with related reporter substrates can explore our Caspase Substrates & Inhibitors collection.
Frequently Asked Questions
What is released when Ac-VQVD-pNA is cleaved?
Caspase-dependent cleavage releases p-nitroaniline, a chromophore that can be measured by absorbance.
Is Ac-VQVD-pNA absolutely selective for caspase-3?
No peptide substrate should be assumed to have absolute selectivity in every assay system. Enzyme composition and experimental conditions should be considered when interpreting cleavage.
Can alternative caspase substrate sequences be synthesized?
Alternative recognition sequences and reporter-group designs can be evaluated through Chemical Peptide Synthesis.