Cathepsin D ELISA Kit (CTSD)


Human cathepsin D ELISA kit can be used to determine in vitro quantitative levels of cathepsin D (CTSD) in human plasma, cell culture supernatant and serum. This assay has a minimum detection limit of < 10.0 pg/ml.


Cathepsin D is an aspartic endo-protease which is found to be distributed ubiquitously in lysosomes, in humans it is encoded by the CTSD gene. The main functions of this protein include degrading proteins and activating precursors of bioactive proteins within pre-lysosomal compartments. This proteinase is a family member of the peptidase A1, it displays specificity which is very similar to but also narrower than that of pepsin A. The catalytic sites of cathepsin D have two critical aspartic residues (33 and 231) which are found to be located on the 14 kDa and 34kDa chains. These two chains are linked by hydrophobic bonds and the mature cathepsin D is made of 337 amino acid residues, with 196 amino acid residues representing the heavy chain and 141 the light chain.

Main functions of cathepsin D includes; degradation of growth factors and polypeptide hormones, processing of enzyme inhibitors and activators, metabolic degradation of intracellular proteins, activation of enzymatic precursors, regulation of programmed cell death and brain antigen processing. Over-expression is found to stimulate metastasis and tumorigenicity, there are also evidence for it initiating tumor apoptosis. This protease has been used as an independent marker of poor prognosis in breast cancer, a useful tool in correlating with the incidence of clinical metastasis.


All reagents supplied need to be stored at 2 °C – 8 °C, unopened reagents will retain reactivity until expiration date. Do not use reagents beyond this date.

  • One 96-Well Plate: Pre-coated with anti-CTSD antibody.
  • Standards: Concentrations 0, 46.875, 93.75, 187.5, 375, 750, 1500, 3000 pg/ml, made up from lyophilized recombinant.
  • Sample/Standard Dilution Buffer.
  • Biotinylated-Labelled Antibody.
  • Antibody Dilution Buffer.
  • HRP-Streptavidin Conjugate (SABC).
  • SABC Dilution Buffer.
  • TMB Substrate.
  • Wash Buffer (25x).
  • Plate Sealer.
  • Product Instructions.


The minimum detection sensitivity level of cathepsin D (CTSD) using current cathepsin-D ELISA kit was 28.125 pg/ml. The dynamic range for this assay is 46.875 – 3,000 pg/ml.


– Specificity: Highly specific for CTSD, no cross reactivity or interference between CTSD and analogues was detected.
– Recovery: Serum (86 – 101%), EDTA Plasma (85 – 104%), Heparin Plasma (88 – 105%).
– Linearity: Serum (91 – 105%), EDTA Plasma (82 – 101%), Heparin Plasma (81 – 99%).
– Precison Intra-Assay: CV < 8%.
– Precison Inter-Assay: CV < 10%.
– Stability: Less than 10%.


  1. Cathepsin D–many functions of one aspartic protease. Crit Rev Oncol Hematol. (2008) 68 (1): 12-28. Review. Benes P., et al.
  2. Significance of the tumor protease cathepsin_D for the biology of breast cancer. Histol Histopathol. (2014) 29 (4): 433-8. Review. Dian D., et al.
  3. Cathepsin D: newly discovered functions of a long-standing aspartic protease in cancer and apoptosis. Cancer Lett. (2006) 237 (2): 167-79. Review. Liaudet-Coopman E., et al.


  • Full Name: Cathepsin D ELISA Kit (CTSD)
  • Reactivity: Human
  • Sample Type: Biological Fluids, Tissue Homogenates, Plasma, Serum
  • Sensitivity: 28.125 pg/ml


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