Recombinant Human Cathepsin D (carrier-free)

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Human CTSD enzyme activity was measured using a fluorogenic peptide substrate Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2. BioLegend’s human FGF-17 product was compared side-by-side to a competitor’s equivalent product.
  • Cathepsin_D_Human_RECOM_BA_013123
    Human CTSD enzyme activity was measured using a fluorogenic peptide substrate Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2. BioLegend’s human FGF-17 product was compared side-by-side to a competitor’s equivalent product.
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556706 100 µg 934€
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Cathepsin D (CTSD) is a major lysosomal aspartic endoproteinase. It is active in acidic conditions with a pH range from 3.5 to 5.0, and its activity is inhibited by pepstatin A. CTSD is involved in lysosomal protein turnover and many other cellular processes. CTSD participates in the resolution of inflammation by initiating the apoptotic program in neutrophils. CTSD is released from neutrophil azurophilic granules during the initial stage of apoptosis, which leads to death receptor-independent activation of caspase-8. CTSD induces apoptosis in other cells as well. In T cells, CTSD activates Bax, which leads to the release of mitochondrial apoptosis-inducing factor (AIF), and subsequently induces an early caspase-independent apoptotic phenotype. CTSD also takes part in the release of cytochrome C from the mitochondria and activation of caspases in fibroblast apoptosis, which is induced by staurosporine. In addition, CTSD participates in cell proliferation, and it increases proliferation and metastatic potential of many cancer cell lines. Overexpression of CTSD has been reported in many different cancers including malignant glioma, melanoma, breast, ovarian, endometrial, and bladder cancer. CTSD is also involved in neurodegenerative diseases. CTSD knockout mice die shortly after birth and display some neurodegeneration phenotypes. Mutations of CTSD cause congenital neuronal ceroid lipofuscinosis in humans and animals. CTSD cleaves the amyloid precursor protein and may play a role in Alzheimer’s disease. CTSD-deficiency has also been associated with Parkinson disease. Like CTSB and CTSL, CTSD functions outside the cells and is able to cleave extracellular matrix proteins including collagen, fibronectin, proteoglycans, and laminin.

Product Details
Technical Data Sheet (pdf)

Product Details

Human Cathepsin D (CTSD), amino acids Leu21-Leu412 (Accession# NP_001900.1) with a C-terminal 10-His tag, was expressed in 293E cells.
Molecular Mass
The 402 amino acid recombinant protein has a predicted molecular mass of approximately 44 kD. The DTT-reduced and non-reduced protein migrate at approximately 50 kD by SDS-PAGE. The predicted N-terminal amino acid is Leu.
>95%, as determined by Coomassie stained SDS-PAGE.
0.22 µm filtered protein solution is in 150 mM NaCl, 20 mM MES, and pH 6.5.
Endotoxin Level
Less than 0.01 ng per µg cytokine as determined by the LAL method.
10 and 25 µg sizes are bottled at 200 µg/mL. 100 µg size and larger sizes are lot-specific and bottled at the concentration indicated on the vial. To obtain lot-specific concentration, please enter the lot number in our Concentration and Expiration Lookup or Certificate of Analysis online tools.
Storage & Handling
Unopened vial can be stored at -20°C for one month, or at -70°C for six months. For maximum results, quick spin vial prior to opening. Avoid repeated freeze/thaw cycles.
After activation, the CTSD activity is determined by its ability to cleave the fluorogenic peptide substrate, Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2. The specific activity is >450 pmol/min/µg.


Application Notes

Step 1: Dilute recombinant human CTSD to 20 µg/ml in assay buffer (0.1 M NaOAc, 0.2 M NaCl, pH 3.5) and incubate the protein at 37°C for 30 min to activate CTSD. After activation, dilute the activated CTSD to 1 ng/µL using assay buffer.
Step 2: Dilute fluorogenic peptide substrate (Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2) to 20 µM using assay buffer.
Step 3: Perform the assay in a 96-well, black, flat-bottom plate. Add 50 µL of the diluted, activated CTSD to a black well and start the reaction by adding 50 µL of the diluted substrate. Assay is read on a fluorometer at excitation and emission wavelengths of 320 nM and 405 nM (top read).

This protein is in the latent form and needs to be activated for bioassay.


BioLegend carrier-free recombinant proteins provided in liquid format are shipped on blue-ice. Our comparison testing data indicates that when handled and stored as recommended, the liquid format has equal or better stability and shelf-life compared to commercially available lyophilized proteins after reconstitution. Our liquid proteins are verified in-house to maintain activity after shipping on blue ice and are backed by our 100% satisfaction guarantee. If you have any concerns, contact us at

Antigen Details

Aspartic endoproteinase.

CTSD is found in most cells and tissues of mammals. It is very abundant in macrophages.

Lysosomal protein turnover, apoptosis, cell proliferation, cell invation, neurodegeneration, and immune responses. Upregulated by estradiol, insulin, insulin-like growth factor, EGF, and FGF basic.
Caspase-8, collagen, fibronectin, proteoglycans, and laminin.
Biology Area
Apoptosis/Tumor Suppressors/Cell Death, Cell Biology, Neurodegeneration, Neuroscience, Neuroscience Cell Markers, Protein Trafficking and Clearance, Stem Cells
Molecular Family
Enzymes and Regulators, Lysosomal Markers
Antigen References

1. Vetvicka V, et al. 1994. 79:131.
2. Johansson AC, et al. 2003. Cell Death Differ. 10:1253.
3. Cavailles V, et al. 1988. Nucleic Acids Res. 16:1903.
4. Bidere N, et al. 2003. J. Biol. Chem. 278:31401.
5. Conus S, et al. 2012. J. Biol. Chem. 25:21142.
6. Koike M, et al. 2001. J. Neurosci. 21:7526.
7. Cullen V, et al. 2009. Mol. Brain. 2:5.
8. Dian D, et al. 2014. Histol. Histopathol. 29:433.

Gene ID
1509 View all products for this Gene ID
View information about Cathepsin D on

Related FAQs

Why choose BioLegend recombinant proteins?

     • Each lot of product is quality-tested for bioactivity as indicated on the data sheet.
     • Greater than 95% Purity or higher, tested on every lot of product.
     • 100% Satisfaction Guarantee for quality performance, stability, and consistency.
     • Ready-to-use liquid format saves time and reduces challenges associated with reconstitution.
     • Bulk and customization available. Contact us.
     • Learn more about our Recombinant Proteins.

How does the activity of your recombinant proteins compare to competitors?

We quality control each and every lot of recombinant protein. Not only do we check its bioactivity, but we also compare it against other commercially available recombinant proteins. We make sure each recombinant protein’s activity is at least as good as or better than the competition’s. In order to provide you with the best possible product, we ensure that our testing process is rigorous and thorough. If you’re curious and eager to make the switch to BioLegend recombinants, contact your sales representative today!

What is the specific activity or ED50 of my recombinant protein?

The specific activity range of the protein is indicated on the product datasheets. Because the exact activity values on a per unit basis can largely fluctuate depending on a number of factors, including the nature of the assay, cell density, age of cells/passage number, culture media used, and end user technique, the specific activity is best defined as a range and we guarantee the specific activity of all our lots will be within the range indicated on the datasheet. Please note this only applies to recombinants labeled for use in bioassays. ELISA standard recombinant proteins are not recommended for bioassay usage as they are not tested for these applications.

Have your recombinants been tested for stability?

Our testing shows that the recombinant proteins are able to withstand room temperature for a week without losing activity. In addition the recombinant proteins were also found to withstand four cycles of freeze and thaw without losing activity.

Does specific activity of a recombinant protein vary between lots?

Specific activity will vary for each lot and for the type of experiment that is done to validate it, but all passed lots will have activity within the established ED50 range for the product and we guarantee that our products will have lot-to-lot consistency. Please conduct an experiment-specific validation to find the optimal ED50 for your system.

How do you convert activity as an ED50 in ng/ml to a specific activity in Units/mg?
Use formula Specific activity (Units/mg) = 10e6/ ED50 (ng/mL)
Go To Top Version: 3    Revision Date: 01/31/2023

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*These products may be covered by one or more Limited Use Label Licenses (see the BioLegend Catalog or our website, BioLegend products may not be transferred to third parties, resold, modified for resale, or used to manufacture commercial products, reverse engineer functionally similar materials, or to provide a service to third parties without written approval of BioLegend. By use of these products you accept the terms and conditions of all applicable Limited Use Label Licenses. Unless otherwise indicated, these products are for research use only and are not intended for human or animal diagnostic, therapeutic or commercial use.


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