• Product name
    Cathepsin K Activity Assay Kit (Fluorometric)
    See all Cathepsin K kits
  • Sample type
    Tissue Extracts, Cell Lysate
  • Assay type
    Enzyme activity
  • Assay time
    2h 00m
  • Product overview

    Cathepsin K Activity Assay Kit (Fluorometric) (ab65303) is a fluorescence-based assay that utilizes the preferred cathepsin K substrate sequence LR labeled with AFC (amino-4-trifluoromethyl coumarin). Cell lysates or other samples that contain cathepsin K will cleave the synthetic substrate LR-AFC to release free AFC. The released AFC can easily be quantified using a fluorometer or fluorescence plate reader.
    Visit our FAQs page for tips and troubleshooting.

  • Notes

    Apoptosis can be mediated by mechanisms other than the traditional caspase-mediated cleavage cascade. There is growing recognition that alternative proteolytic enzymes such as the lysosomal cathepsin proteases may initiate or propagate proapoptotic signals. Cathepsins are lysosomal enzymes that are also used as sensitive markers in various toxicological investigations.


  • Storage instructions
    Store at -20°C. Please refer to protocols.
  • Components Identifier 100 tests
    CK Cell Lysis Buffer WM 1 x 25ml
    CK Inhibitor (1mM) Red 1 x 1µl
    CK Reaction Buffer NM 1 x 5ml
    CK Substrate Ac-LR-AFC (10mM) Amber 1 x 200µl
  • Research areas
  • Relevance
    Cathepsin K is closely involved in osteoclastic bone resorption and may participate partially in the disorder of bone remodeling. Displays potent endoprotease activity against fibrinogen at acid pH. May play an important role in extracellular matrix degradation.
  • Cellular localization
  • Alternative names
    • Cathepsin O
    • Cathepsin O2
    • Cathepsin X
    • CTSK
    • CTSO
    • CTSO2
    see all


  • Cathepsin K Activity measured in tissue lysates (each with protein concentration of 4 mg/mL) after 1 hour of incubation with and without inhibitor (I).

  • Cathepsin K Activity measured in cell lysates (each with cells concentration of 4e7 cells/mL) after 1 hour of incubation with and without inhibitor (I).



This product has been referenced in:
  • Park HJ  et al. 4-Phenylbutyric acid protects against lipopolysaccharide-induced bone loss by modulating autophagy in osteoclasts. Biochem Pharmacol 151:9-17 (2018). Read more (PubMed: 29458048) »
  • Chakraborty S  et al. Pasteurella multocida Toxin Triggers RANKL-Independent Osteoclastogenesis. Front Immunol 8:185 (2017). Read more (PubMed: 28289415) »

See all 3 Publications for this product

Customer reviews and Q&As

I have good news!

AFC is now available for purchase. This is catalog number ab129872.


I hope this is helpful. Please contact me again if you have an...

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I am currently looking into whether or not we can make AFC available on our catalog. I will follow up with you as soon as I have further details.

Thanks for your patience!

Thank you for your reply. I have asked the lab for any data or references that they might have regarding the specificity of the substrates, and I will forward this information to you once I hear from them. Please let me know if you have a...

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Thank you for your call yesterday and for your question about ab65302 and ab65303. I have heard back from the lab and we do not expect these kits to cross-react with other enzymes. I hope this information is useful, but please let me know...

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