• Product name
    Cathepsin L Activity Assay Kit (Fluorometric)
    See all Cathepsin L kits
  • Sample type
    Serum, Plasma, Cell Lysate, Tissue Lysate
  • Assay type
    Enzyme activity
  • Assay time
    2h 00m
  • Species reactivity
    Reacts with: Human
    Predicted to work with: Mammal
  • Product overview

    Abcam's Cathepsin L Activity Assay Kit is a fluorescence-based assay that utilizes the preferred cathepsin-L substrate sequence FR labeled with AFC (amino-4-trifluoromethyl coumarin). Cell lysates or other samples that contain cathepsin L will cleave the synthetic substrate FR-AFC to release free AFC, which can be measured in a spectrophotometer at Em = 505 nm. The amount of free AFC will be directly proportional to the cathepsin L activity found in the sample.

    Visit our FAQs page for tips and troubleshooting.

  • Notes

    Cathepsin L plays a major role in antigen processing, tumor invasion and metastasis, bone resorption, and turnover of intracellular and secreted proteins involved in growth regulation. Although commonly recognized as a lysosomal protease, cathepsin L is also secreted. This broad-spectrum protease is potent in degrading several extracellular proteins (laminins, fibronectin, collagens I and IV, elastin, and other structural proteins of basement membranes) as well as serum proteins and cytoplasmic and nuclear proteins.


    If you need additional Ac-FR-AFC substrate (10mM), it is avaible for purchasing as ab157769.

  • Tested applications
    Suitable for: Functional Studiesmore details


  • Storage instructions
    Store at -20°C. Please refer to protocols.
  • Components Identifier 100 tests
    Assay Buffer 1 x 30ml
    CL Inhibitor (1 mM) Red 1 x 20µl
    CL Positive Control (human) 1 vial
    CL Substrate Ac-FR-AFC (10 mM) Brown 1 x 200µl
    DTT 1 x 100µl
  • Research areas
  • Relevance
    Cathepsin L is a lysosomal cysteine proteinase that plays a major role in intracellular protein catabolism. Its substrates include collagen and elastin, as well as alpha 1 protease inhibitor, a major controlling element of neutrophil elastase activity. Cathepsin L has been implicated in several pathologic processes, including rheumatoid arthritis, muscular dystrophy, Alzheimers, cancer, myofibril necrosis in myopathies and in myocardial ischemia, and in the renal tubular response to proteinuria. Cathepsin L, which is a member of the peptidase C1 family, is a dimer composed of disulfide linked heavy and light chains, both produced from a single protein precursor. At least two transcript variants encoding the same protein have been found for its gene.
  • Cellular localization
  • Alternative names
    • Cathepsin L1
    • CathepsinL
    • CATL
    • CTSL
    • CTSL1
    • Major excreted protein
    • MEP
    see all
  • Database links


Our Abpromise guarantee covers the use of ab65306 in the following tested applications.

The application notes include recommended starting dilutions; optimal dilutions/concentrations should be determined by the end user.

Application Abreviews Notes
Functional Studies Use at an assay dependent dilution.


  • Nuclear Cathepsin L activity measured in the arcuate nucleus of: Column 1: wt lean mice, saline injected intraperitoneally; Column 2: wt fasted mice, saline injected intraperitoneally; Column 3: wt fasted mice, leptin injected intraperitoneally (1µg/g total body weight); Column 4: wt lean mice, placed in a 4C cold room for 4h; Column 5: Lepob mice, saline injected intraperitoneally; Column 6: wt lean mice, leptin and Cathepsin L inhibitor I in corn oil injected intraperitoneally (15µg/g total body weight). *,statiscally significant (p<0.01)

    Image obtained from Stratigopoulos G et al; JBC, 2011 Jan 21;286(3):2155-70

  • Cathepsin L activity in cell lysates (duplicates +/- SD). Data from lysates corresponding to 0.5-2 million cells per well.

  • Cathepsin L activity in biological fluids (serum in the range of neat-1/27 dilution, plasma neat; duplicates +/- SD)



This product has been referenced in:
  • Zhang J  et al. Palmitate impairs angiogenesis via suppression of cathepsin activity. Mol Med Rep 15:3644-3650 (2017). Read more (PubMed: 28440480) »
  • Marzuca-Nassr GN  et al. Balanced Diet-Fed Fat-1 Transgenic Mice Exhibit Lower Hindlimb Suspension-Induced Soleus Muscle Atrophy. Nutrients 9:N/A (2017). Read more (PubMed: 28984836) »

See all 9 Publications for this product

Customer reviews and Q&As

Based on the data on the datasheet from human and mouse samples, the assay measures activity of both L1 and L2, assuming mice do not have a gene for L1. The assay depends on preferential recognition of the FR sequence substrate(phenylalanine-arginine) ...

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We do not recommend to prepare one lysate to use with ab65302, ab65306 and ab65307.
It is important to prepare separate lysates for each kit, using the specific lysis buffer provided. This is because the cathepsins have very specific pH and other c...

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