Recombinant Human Cystatin F Protein, CF


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Product Details

Reactivity HuSpecies Glossary
Applications Inhibition Activity

Order Details

Recombinant Human Cystatin F Protein, CF Summary

Details of Functionality
Measured by its ability to inhibit active Cathepsin L cleavage of a fluorogenic peptide substrate Z-LR-AMC (Catalog # ES008). The IC50 value is <6.0 nM, as measured under the described conditions.
Mouse myeloma cell line, NS0-derived human Cystatin F protein
Gly20-His145, with a C-terminal 6-His tag
Accession #
N-terminal Sequence
Structure / Form
Disulfide-linked homodimer
Protein/Peptide Type
Recombinant Enzymes
>95%, by SDS-PAGE under reducing conditions and visualized by silver stain
Endotoxin Note
<1.0 EU per 1 μg of the protein by the LAL method.


Theoretical MW
15 kDa.
Disclaimer note: The observed molecular weight of the protein may vary from the listed predicted molecular weight due to post translational modifications, post translation cleavages, relative charges, and other experimental factors.
16 kDa, 21 kDa and 26 kDa, reducing conditions
Read Publications using
1889-PI in the following applications:

Packaging, Storage & Formulations

Use a manual defrost freezer and avoid repeated freeze-thaw cycles.
  • 6 months from date of receipt, -20 to -70 °C as supplied.
  • 3 months, -20 to -70 °C under sterile conditions after reconstitution.
Lyophilized from a 0.2 μm filtered solution in Tris and NaCl.
>95%, by SDS-PAGE under reducing conditions and visualized by silver stain
Reconstitution Instructions
Reconstitute at 100 μg/mL in sterile 25 mM Tris and 150 mM NaCl, pH 7.5.
Assay Procedure
  • Assay Buffer: 50 mM MES, pH 6.0
  • Dithiothreitol (DTT) (Sigma, Catalog # D0632), 1 M stock in deionized water
  • Recombinant Human Cystatin F (rhCystatin F) (Catalog # 1889-PI)
  • Recombinant Human Cathepsin L (rhCathepsin L) (Catalog # 952-CY)
  • Substrate: Z-Leu-Arg-AMC (Catalog # ES008), 10 mM stock in DMSO
  • F16 Black Maxisorp Plate (Nunc, Catalog # 475515)
  • Fluorescent Plate Reader (Model: SpectraMax Gemini EM by Molecular Devices) or equivalent
  1. Dilute rhCathepsin L to 1 µg/mL in Assay Buffer with 5 mM DTT.
  2. Incubate on ice for 15 minutes.
  3. After incubation, dilute activated rhCathepsin L to 0.5 µg/mL in Assay Buffer.
  4. Prepare a curve of rhCystatin F (MW: 15,356 Da) in Assay Buffer. Make the following serial dilutions: 2000, 1000, 500, 250, 125, 62.5, 31.3, 15.6, 7.8, and 3.9 nM.
  5. Gently mix equal volumes of the rhCystatin F curve dilutions and the diluted active rhCathepsin L. Include a control (in duplicate) containing Assay Buffer and the diluted active rhCathepsin L.
  6. Incubate mixtures at room temperature for 15 minutes.
  7. Make a five-fold dilution of reaction mixture with Assay Buffer.
  8. Dilute Substrate to 20 µM in Assay Buffer.
  9. Load 50 µL of the incubated mixtures into a black well plate, and start the reaction by adding 50 µL of 20 µM Substrate.
  10. Read at excitation and emission wavelengths of 380 nm and 460 nm (top read), respectively, in kinetic mode for 5 minutes.
  11. Derive 50% inhibition concentration (IC50) value for rhCystatin F by plotting RFU/min (or specific activity) versus concentration with 4‑PL fitting.
  12. The specific activity for rhCathepsin L at each point may be determined using the following formula (if needed):

     Specific Activity (pmol/min/µg) =

Adjusted Vmax* (RFU/min) x Conversion Factor** (pmol/RFU)
amount of enzyme (µg)

     *Adjusted for Substrate Blank
     **Derived using calibration standard 7-amino, 4-Methyl Coumarin (Sigma, Catalog # A-9891).

Per Well:
  • rhCathepsin L: 0.0025 µg
  • rhCystatin F curve: 100, 50, 25, 12.5, 6.25, 3.13, 1.56, 0.78, 0.39 and 0.20 nM
  • Substrate: 10 µM


This product is produced by and ships from R&D Systems, Inc., a Bio-Techne brand.

Alternate Names for Recombinant Human Cystatin F Protein, CF

  • CMAP
  • CST7
  • Cystatin 7
  • cystatin F (leukocystatin)
  • Cystatin F
  • Cystatin-7
  • cystatin-F
  • Cystatin-like metastasis-associated protein
  • Leukocystatin


Cystatin F, also known as leukocystatin and CMAP (Cystatin‑like Metastasis‑Associated Protein), is a member of the cystatin superfamily (1‑3). Cystatin F is selectively expressed by hematopoietic cells and may be a biomarker for both liver metastasis and inflammatory lung disorders (3, 4). As a cysteine protease inhibitor, it shows selectivity towards cathepsin L and legumain (1, 2, 5). Compared to other secreted cystatins including C, D, E/M, S, SA and SN, which contain two intra disulfide bonds, cystatin F has two extra Cys residues that may be involved in inter disulfide bonds. Indeed, rhCystatin F showed disulfide bond‑linked dimer formation, which was also the case for an E. coli expressed fusion protein containing mature human cystatin F and glutathione S‑transferase (2).

  1. Ni, J. et al. (1998) J. Biol. Chem. 273:24797.
  2. Halfon, S. et al. (1998) J. Biol. Chem. 273:16400.
  3. Utsunomiya, T. et al. (2002) Clin Cancer 8:2591
  4. Werle, B. et al. (2003) Biol. Chem. 384:281.
  5. Gruninger-Leitch, F. et al. (2000) Nat. Biotechnol. 18:66.

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Gene Symbol CST7