Recombinant Human Carboxypeptidase A4/CPA4 Protein, CF

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Recombinant Human Carboxypeptidase A4/CPA4 Protein, CF Summary

Product Specifications

>95%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining.
Endotoxin Level
<1.0 EU per 1 μg of the protein by the LAL method.
Measured by its ability to cleave the colorimetric peptide substrate Ac-Phe-Thiaphe-OH in the presence of 5,5’Dithio-bis (2-nitrobenzoic acid) (DTNB). Edwards, K.M. et al. (1999) J. Biol. Chem. 274:30468. The specific activity is >3,500 pmol/min/μg, as measured under the described conditions.
Mouse myeloma cell line, NS0-derived human Carboxypeptidase A4/CPA4 protein
Gly17-Tyr421, with a C-terminal 10-His tag
Accession #
N-terminal Sequence
Structure / Form
Predicted Molecular Mass
47 kDa
48 kDa, reducing conditions

Product Datasheets

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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 Supplied as a 0.2 μm filtered solution in Tris and NaCl.
Shipping The product is shipped with polar packs. 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 opening.

Assay Procedure

  • Activation Buffer: 50 mM Tris, 10 mM CaCl2, 150 mM NaCl, 0.05% (w/v) Brij-35, pH 7.5 (TCNB)
  • Assay Buffer: 50 mM Tris, pH 8.0
  • Recombinant Human Carboxypeptidase A4/CPA4 (rhCPA4) (Catalog # 5906-ZN)
  • Recombinant Human Active Trypsin 3/PRSS3 (rhTrypsin 3) (Catalog # 3714-SE)
  • AEBSF (Catalog # EI001), 100 mM in deionized water
  • Substrate: N-Acetyl-L-Phenylalanyl-L-3-Thiaphenylalanine (Peptides International, Catalog # STP-3621-PI),10 mM stock in DMSO
  • 5,5’-dithio-bis(2-nitrobenzoic acid) (DTNB) (Sigma, Catalog # D-8130), 10 mM stock in DMSO
  • 96 well clear plate (Costar, Catalog # 92592)
  • Plate Reader (Model: SpectraMax Plus by Molecular Devices) or equivalent
  1. Dilute rhCPA4 to 100 µg/mL with 1.0 µg/mL rhTrypsin 3 in Activation Buffer.
  2. Incubate at 37 °C for 2.5 hours.
  3. Stop rhTrypsin 3 activity by adding AEBSF at a final concentration of 1 mM.
  4. Incubate at room temperature for 15 minutes.
  5. Dilute activated rhCPA4 to 0.2 µg/mL in Assay Buffer.
  6. Dilute Substrate to 200 µM with 200 µM DTNB in Assay Buffer (prepare immediately before use).
  7. Load 50 µL of the 0.2 µg/mL rhCPA4 into a plate, and start the reaction by adding 50 µL of Substrate/DTNB mixture. Include a Substrate Blank with 50 µL of Assay Buffer and 50 µL of Substrate/DTNB mixture.
  8. Read in kinetic mode for 5 minutes at an absorbance of 405 nm.
  9. Calculate specific activity using the following formula:

     Specific Activity (pmol/min/µg) =

Adjusted Vmax* (OD/min) x well volume (L) x 1012 pmol/mol
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 Per Well:
  • rhCPA4: 0.01 µg
  • Substrate: 100 µM
  • DTNB: 100 µM
Reconstitution Calculator

Reconstitution Calculator

The reconstitution calculator allows you to quickly calculate the volume of a reagent to reconstitute your vial. Simply enter the mass of reagent and the target concentration and the calculator will determine the rest.


Background: Carboxypeptidase A4/CPA4

Carboxypeptidase A4, also known as CPA4, is a secreted, zinc-dependent metallocarboxypeptidase that removes the C-terminal amino acid from peptides having a free C-terminal carboxyl group. CPA4 can hydrolyze both amide and ester bonds and has a preference for cleavage at the amino side of hydrophobic residues. CPA4 is inhibited by latexin, an endogenous inhibitor of carboxypeptidases (1). The deduced amino acid sequence of human CPA4 consists of a signal peptide (residues 1‑16), a pro region (17‑113), and a mature chain (residues 114‑421).  The CPA4 gene has been associated with prostate cancer aggressiveness and is involved in the histone hyperacetylation signaling pathway (2, 3).  Recent studies show that coding variation in the CPA4 gene is linked to high risk prostate cancer among younger patients (4).

  1. Pallares, I. et al. (2005) Proc. Natl. Acad. Sci. USA 102:3978.
  2. Kayashima, T. et al. (2003) Hum. Genet. 3:220.
  3. Huang, H. et al. (1999) Cancer Research. 59:2981.
  4. Ross, P.L. et al. (2009) BMC Cancer. 9:69.
Entrez Gene IDs
51200 (Human); 71791 (Mouse)
Alternate Names
Carboxypeptidase A3; Carboxypeptidase A4; CPA3EC 3.4.17; CPA4; EC 3.4.17.-; EC


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