Measured by its ability to inhibit Granzyme B cleavage of tert-butoxycarbonyl-Ala-Ala-Asp-thiobenzyl ester (Boc-AAD-SBzl). The IC50 is <25 nM, as measured under the described conditions.
Source
Mouse myeloma cell line, NS0-derived mouse Serpin A3N protein Phe21-Lys418, with a C-terminal 6-His tag
>85%, 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.
Applications/Dilutions
Dilutions
Inhibition Activity
Theoretical MW
46 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.
SDS-PAGE
59 kDa, reducing conditions
Publications
Read Publications using 4709-PI in the following applications:
Recombinant Human Granzyme B (rhGranzyme B) (Catalog # 2906-SE)
Recombinant Mouse Active Cathepsin C/DPPI (rmCathepsin C) (Catalog # 2336-CY)
E-64 (Sigma, Catalog # E-3132), 1 mM stock in DMSO
DTNB (5,5’-dithio-bis (2-nitrobenzoic acid) (Sigma, Catalog # D-8130), 10 mM stock in DMSO
Substrate: tert-Butoxycarbonyl-Ala-Ala-Asp-thiobenzyl ester (SM Biochemicals LLC, Catalog # SMSB05), 10 mM stock in DMSO
96-well Clear Plate (Costar, Catalog # 92592)
Plate reader (Model: SpectraMax Plus by Molecular Devices) or equivalent
Activate rhGranzyme B by diluting to 100 µg/mL with 10 µg/mL of rmCathepsin C in Activation Buffer.
Incubate at 37 °C for 4 hours.
Stop reaction with E-64 at final a concentration of 10 µM in Activation Buffer.
Prepare a curve of rmSerpin A3N (MW: 45551 Da) in Assay Buffer. Make the following serial dilutions: 5000, 2500, 1000, 800, 650, 500, 250, 125, 50, and 10 nM.
Dilute activated rhGranzyme B to 12.5 µg/mL in Assay Buffer.
Combine 20 µL of 12.5 µg/mL rhGranzyme B with 20 µL of the rmSerpin A3N serial curve dilutions. Include two enzyme controls of 20 µL of 12.5 µg/mL rhGranzyme B with 20 µL Assay Buffer.
Incubate mixtures at room temperature for 30 minutes.
Dilute mixtures by adding 460 µL Assay Buffer to each.
Dilute Substrate to 200 µM containing 200 µM of DTNB in Assay Buffer.
In a plate load 50 µL of the diluted mixtures into wells.
Start the reaction by adding 50 µL of 200 µM Substrate mixture.
Read at a wavelength of 405 nm in kinetic mode for 5 minutes.
Derive the 50% inhibiting concentration (IC50) for rmSerpin A3N by plotting OD/min (or specific activity) vs. concentration with 4-PL fitting.
The specific activity for rhGranzyme B at each point may be determined using the following formula (if needed):
Specific Activity (pmol/min/µg) =
Adjusted Vmax* (OD/min) x well volume (L) x 1012 pmol/M
ext. coeff** (M-1cm-1) x path corr.*** (cm) x amount of enzyme (µg)
*Adjusted for Substrate Blank
**Using the extinction coefficient 13260 M-1cm-1
***Using the path correction 0.32 cm
Note: the output of many spectrophotometers is in mOD.
Serpin A3N is a serine protease inhibitor that is structurally related to alpha 1-antichymotrypsin encoded by the SERPINA3 gene (1). Serpin A3N is highly expressed in brain, testis, lung, thymus, and spleen (2). Serpin A3N secreted by Sertoli cells may regulate the activity of locally produced Granzyme B (3). Granzyme B inhibition by Serpin A3N may therefore regulate Granzyme B-mediated killing by cytotoxic lymphocytes, providing a means to disable cell-mediated immune responses.
Forsyth, S. et al. (2003) Genomics 81:336.
Horvath, A. J. et al. (2004) J. Mol. Evol. 59:488.
Hirst, C. E. et al. (2001) Mol. Hum. Reprod. 7:1133.
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