Recombinant Human SLPI Protein, CF

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Citations (20)
Supplemental Products
Reviews (1)

Recombinant Human SLPI Protein, CF Summary

>97%, by SDS-PAGE under reducing conditions and visualized by silver stain
Endotoxin Level
<1.0 EU per 1 μg of the protein by the LAL method.
Measured by its ability to inhibit trypsin cleavage of a fluorogenic peptide substrate, Mca-RPKPVE-Nval-WRK(Dnp)-NH2 (Catalog # ES002). The IC50 value is <4.0 nM, under the described conditions.
E. coli-derived human SLPI protein
Accession #
N-terminal Sequence
Predicted Molecular Mass
12 kDa
13 kDa, reducing conditions

Product Datasheets

Carrier Free

What does CF mean?

CF stands for Carrier Free (CF). We typically add Bovine Serum Albumin (BSA) as a carrier protein to our recombinant proteins. Adding a carrier protein enhances protein stability, increases shelf-life, and allows the recombinant protein to be stored at a more dilute concentration. The carrier free version does not contain BSA.

What formulation is right for me?

In general, we advise purchasing the recombinant protein with BSA for use in cell or tissue culture, or as an ELISA standard. In contrast, the carrier free protein is recommended for applications, in which the presence of BSA could interfere.


Formulation Lyophilized from a 0.2 μm filtered solution in PBS.
Reconstitution Reconstitute at 500 μg/mL in sterile PBS.
Shipping The product is shipped at ambient temperature. Upon receipt, store it immediately at the temperature recommended below.
Stability & Storage: 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.

Assay Procedure

  • Assay Buffer: 50 mM Tris, 10 mM CaCl2, 150 mM NaCl, 0.05% Brij-35 (v/v), pH 7.5 (TCNB)
  • Recombinant Human SLPI (rhSLPI) (Catalog # 1274-PI)
  • Trypsin (Sigma, Catalog # T-1426)
  • Substrate: MCA-Arg-Pro-Lys-Pro-Val-Glu-NVAL-Trp-Arg-Lys(DNP)-NH2 (Catalog # ES002), 2 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 Trypsin to 0.25 µg/mL in Assay Buffer.
  2. Prepare a curve of rhSLPI (MW: 11,726 Da) in Assay Buffer. Make the following serial dilutions: 5000, 500, 250, 125, 83.8, 55.6, 37, 24.7, 8.23, and 2.06 nM.
  3. Mix 25 µL of 0.25 µg/mL Trypsin and 25 µL of the rhSLPI dilutions. Include an enzyme control (in duplicate) of 25 µL Assay Buffer and 25 µL of 0.25 µg/mL Trypsin.
  4. Incubate reaction mixtures at 37 °C for 60 minutes.
  5. Dilute Substrate to 20 µM in Assay Buffer.
  6. After incubation dilute the enzyme inhibitor mixtures five fold in Assay Buffer.
  7. In a plate load 50 µL of the diluted reaction mixtures to wells.
  8. Start the reaction by adding 50 µL of 20 µM Substrate to wells.
  9. Read at excitation and emission wavelengths of 320 nm and 405 nm (top read), respectively in kinetic mode for 5 minutes.
  10. Derive the IC50 value for rhSLPI from the curve.
  11. Calculate specific activity for each point 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 MCA-Pro-Leu-OH (Bachem, Catalog # M-1975).

Per Well:
  • Trypsin: 0.00125 µg
  • rhSLPI curve: 250, 25, 12.5, 6.25, 4.19, 2.78, 1.85, 1.235, 0.415, 0.103 and 0 nM
  • Substrate: 10 µM
Reconstitution Calculator

Reconstitution Calculator

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Background: SLPI

Secretory Leukocyte Protease Inhibitor (SLPI) is a protein found in various secretory fluids, including parotid secretions, bronchial, nasal and cervical mucus, and seminal fluid. The protein is a potent inhibitor of a variety of proteolytic enzymes, including the neutrophil proteases, elastase and cathepsin G and the pancreatic proteases chymotrypsin and trypsin. SLPI is an important component of the antiprotease defense of tissues bathed by secretory fluids. It could be used as a therapeutic agent for treatment of the proteolytic damage of tissues seen in degenerative and inflammatory diseases.

Long Name
Secretory Leukocyte Protease Inhibitor
Entrez Gene IDs
6590 (Human); 20568 (Mouse)
Alternate Names
ALK1; ALPProtease inhibitor WAP4; antileukoproteinase; BLPISeminal proteinase inhibitor; HUSI; HUSI-I; Mucus proteinase inhibitor; secretory leukocyte peptidase inhibitor; secretory leukocyte protease inhibitor (antileukoproteinase); Secretory leukocyte protease inhibitor; SLPI; WAP four-disulfide core domain protein 4; WAP4HUSI-1; WFDC4MPI

Citations for Recombinant Human SLPI Protein, CF

R&D Systems personnel manually curate a database that contains references using R&D Systems products. The data collected includes not only links to publications in PubMed, but also provides information about sample types, species, and experimental conditions.

20 Citations: Showing 1 - 10
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  1. Characterisation of the Major Extracellular Proteases of Stenotrophomoas maltophilia and Their Effects on Pulmonary Antiproteases
    Authors: K Molloy, SG Smith, G Cagney, ET Dillon, CM Greene, NG McElvaney
    Pathogens, 2019;8(3):.
    Species: Bacteria - Stenotrophomonas maltophilia
    Sample Types: Cell Culture Supernates
    Applications: Bioassay
  2. Externalized histone H4 orchestrates chronic inflammation by inducing lytic cell death
    Authors: C Silvestre-, Q Braster, K Wichapong, EY Lee, JM Teulon, N Berrebeh, J Winter, JM Adrover, GS Santos, A Froese, P Lemnitzer, A Ortega-Góm, R Chevre, J Marschner, A Schumski, C Winter, L Perez-Oliv, C Pan, N Paulin, T Schoufour, H Hartwig, S González-R, F Kamp, RTA Megens, KA Mowen, M Gunzer, L Maegdefess, T Hackeng, E Lutgens, M Daemen, J von Blume, HJ Anders, VO Nikolaev, JL Pellequer, C Weber, A Hidalgo, GAF Nicolaes, GCL Wong, O Soehnlein
    Nature, 2019;569(7755):236-240.
    Species: Human
    Sample Types: Protein
    Applications: Bioassay
  3. MerTK expressing hepatic macrophages promote the resolution of inflammation in acute liver failure
    Authors: E Triantafyl, OT Pop, LA Possamai, A Wilhelm, E Liaskou, A Singanayag, C Bernsmeier, W Khamri, G Petts, R Dargue, SP Davies, J Tickle, M Yuksel, VC Patel, RD Abeles, Z Stamataki, SM Curbishley, Y Ma, ID Wilson, M Coen, KJ Woollard, A Quaglia, J Wendon, MR Thursz, DH Adams, CJ Weston, CG Antoniades
    Gut, 2017;0(0):.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  4. Elafin drives poor outcome in high-grade serous ovarian cancers and basal-like breast tumors.
    Authors: Labidi-Galy S, Clauss A, Ng V, Duraisamy S, Elias K, Piao H, Bilal E, Davidowitz R, Lu Y, Badalian-Very G, Gyorffy B, Kang U, Ficarro S, Ganesan S, Mills G, Marto J, Drapkin R
    Oncogene, 2015;34(3):373-83.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  5. Proresolving Actions of Synthetic and Natural Protease Inhibitors Are Mediated by Annexin A1.
    Authors: Vago J, Tavares L, Sugimoto M, Lima G, Galvao I, de Caux T, Lima K, Ribeiro A, Carneiro F, Nunes F, Pinho V, Perretti M, Teixeira M, Sousa L
    J Immunol, 2015;196(4):1922-32.
    Species: Mouse
    Sample Types: In Vivo
    Applications: In Vivo
  6. Inhibition of Langerhans cell maturation by human papillomavirus type 16: a novel role for the annexin A2 heterotetramer in immune suppression.
    Authors: Woodham A, Raff A, Raff L, Da Silva D, Yan L, Skeate J, Wong M, Lin Y, Kast W
    J Immunol, 2014;192(10):4748-57.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  7. Staphylococcus aureus secretes a unique class of neutrophil serine protease inhibitors.
    Authors: Stapels D, Ramyar K, Bischoff M, von Kockritz-Blickwede M, Milder F, Ruyken M, Eisenbeis J, McWhorter W, Herrmann M, van Kessel K, Geisbrecht B, Rooijakkers S
    Proc Natl Acad Sci U S A, 2014;111(36):13187-92.
    Species: N/A
    Sample Types: Protein
    Applications: Bioassay
  8. Quantitative proteomic analysis of oral brush biopsies identifies secretory leukocyte protease inhibitor as a promising, mechanism-based oral cancer biomarker.
    Authors: Yang, Ya, Rhodus, Nelson L, Ondrey, Frank G, Wuertz, Beverly, Chen, Xiaobing, Zhu, Yaqin, Griffin, Timothy
    PLoS ONE, 2014;9(4):e95389.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  9. Secretory leukocyte protease inhibitor reverses inhibition by CNS myelin, promotes regeneration in the optic nerve, and suppresses expression of the transforming growth factor-beta signaling protein Smad2.
    Authors: Hannila S, Siddiq M, Carmel J, Hou J, Chaudhry N, Bradley P, Hilaire M, Richman E, Hart R, Filbin M
    J Neurosci, 2013;33(12):5138-51.
    Species: Rat
    Sample Types: In Vivo
    Applications: In Vivo
  10. Regulation of progranulin expression in human microglia and proteolysis of progranulin by matrix metalloproteinase-12 (MMP-12).
    Authors: Suh HS, Choi N, Tarassishin L, Lee SC
    PLoS ONE, 2012;7(4):e35115.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  11. Inhibition of SLPI ameliorates disease activity in experimental autoimmune encephalomyelitis.
    Authors: Muller AM, Jun E, Conlon H, Sadiq SA
    BMC Neurosci, 2012;13(0):30.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  12. Dysregulation of TIM-3-Galectin-9 Pathway in the Cystic Fibrosis Airways.
    Authors: Vega-Carrascal I, Reeves EP, Niki T, Arikawa T, McNally P, O'Neill SJ, Hirashima M, McElvaney NG
    J. Immunol., 2011;0(0):.
    Species: Human
    Sample Types: BALF
    Applications: Bioassay
  13. The secretory leukocyte protease inhibitor (SLPI) and the secondary granule protein lactoferrin are synthesized in myelocytes, colocalize in subcellular fractions of neutrophils, and are coreleased by activated neutrophils.
    Authors: Jacobsen LC, Sorensen OE, Cowland JB, Borregaard N, Theilgaard-Monch K
    J. Leukoc. Biol., 2008;83(5):1155-64.
    Species: N/A
    Sample Types: N/A
    Applications: Western Blot
  14. Use of an immunoaffinity-mass spectrometry-based approach for the quantification of protein biomarkers from serum samples of lung cancer patients.
    Authors: Nicol GR, Han M, Kim J, Birse CE, Brand E, Nguyen A, Mesri M, FitzHugh W, Kaminker P, Moore PA, Ruben SM, He T
    Mol. Cell Proteomics, 2008;7(10):1974-82.
    Species: N/A
    Sample Types: N/A
    Applications: Standard
  15. The alarm anti-protease, secretory leukocyte protease inhibitor, is a proliferation and survival factor for ovarian cancer cells.
    Authors: Simpkins FA, Devoogdt NM, Rasool N, Tchabo NE, Alejandro EU, Kamrava MM, Kohn EC
    Carcinogenesis, 2007;29(3):466-72.
    Species: N/A
    Sample Types: N/A
    Applications: Western Blot
  16. Epithelial cells trigger frontline immunoglobulin class switching through a pathway regulated by the inhibitor SLPI.
    Authors: Xu&lt;/LastName&gt;&lt;ForeName&gt;We W&lt;/Initial, Xu W, He B, Chiu A, Chadburn A, Shan M, Buldys M, Ding A, Knowles DM, Santini PA, Cerutti A
    Nat. Immunol., 2007;8(3):294-303.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  17. Streptococcal DRS (distantly related to SIC) and SIC inhibit antimicrobial peptides, components of mucosal innate immunity: a comparison of their activities.
    Authors: Fernie-King BA, Seilly DJ, Binks MJ, Sriprakash KS, Lachmann PJ
    Microbes Infect., 2007;9(3):300-7.
    Species: Bacteria
    Sample Types: Whole Cells
    Applications: Bioassay
  18. Arginine-specific gingipains from Porphyromonas gingivalis deprive protective functions of secretory leucocyte protease inhibitor in periodontal tissue.
    Authors: Into T, Inomata M, Kanno Y, Matsuyama T, Machigashira M, Izumi Y, Imamura T, Nakashima M, Noguchi T, Matsushita K
    Clin. Exp. Immunol., 2006;145(3):545-54.
    Species: Human
    Sample Types: Whole Cells
    Applications: Bioassay
  19. Mannan-binding lectin-associated serine protease 3 cleaves synthetic peptides and insulin-like growth factor-binding protein 5.
    Authors: Cortesio CL, Jiang W
    Arch. Biochem. Biophys., 2006;449(1):164-70.
    Species: N/A
    Sample Types: Protein
    Applications: Enzyme Assay
  20. Membrane protease proteomics: Isotope-coded affinity tag MS identification of undescribed MT1-matrix metalloproteinase substrates.
    Authors: Tam EM, Morrison CJ, Wu YI, Stack MS, Overall CM
    Proc. Natl. Acad. Sci. U.S.A., 2004;101(18):6917-22.
    Species: Human
    Sample Types: Cell Culture Supernates
    Applications: Enzyme Assay


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Recombinant Human SLPI Protein, CF
By Anonymous on 12/24/2018
Application: Immunoassay Standard
Reason for Rating: Great