Recombinant Human P4HB Protein, CF

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R&D Systems Recombinant Proteins and Enzymes
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Product Details

Recombinant Human P4HB Protein, CF Summary

Product Specifications

>80%, 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 promote aggregation of insulin in the presence of DTT. The specific activity is >7.5 A650/cm/min/mg, as measured under the described conditions.
Chinese Hamster Ovary cell line, CHO-derived human Protein Disulfide Isomerase/P4HB protein
Asp18-Lys505, with a C-terminal 10-His tag
Accession #
N-terminal Sequence
Predicted Molecular Mass
56 kDa
60 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, NaCl and Glycerol.
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

  • Buffer A: 100 mM NaH2PO4, 3 mM DTT, pH 7.0
  • Buffer B: 100 mM NaH2PO4, 3 mM EDTA, pH 7.0
  • Recombinant Human Protein Disulfide Isomerase/P4HB (rhP4HB) (Catalog # 4236-DI)
  • Insulin (Sigma, Catalog # I-5500), 10 mg/mL solution in 50 mM Tris, pH 7.5 (solution will be cloudy)
  • 96-well Clear Plate (Costar, Catalog # 92592)
  • Plate Reader (Model: SpectraMax Plus by Molecular Devices) or equivalent
  1. Dilute insulin to 1.5 mg/mL in Buffer B.
  2. Incubate diluted insulin for 10 minutes at room temperature (insulin will solubilize).
  3. Dilute rhP4HB to 45 µg/mL in Buffer A.
  4. Mix 100 µL of 45 µg/mL rhP4HB and 200 µL of 1.5 mg/mL insulin. Create a Substrate Blank with 100 µL Buffer A and 200 µL insulin.
  5. Incubate at room temperature for 20 minutes.
  6. Load in a clear 96-well plate 100 µL from each reaction vial in duplicate.
  7. Read at 650 nm (absorbance) in kinetic mode for 5 minutes.
  8. Calculate specific activity:

     Specific Activity (Abs/cm/min/mg) =

Adjusted Vmax* (Abs/min)**
path corr.(cm)*** x amount of enzyme (mg)

     *Adjusted for Substrate Blank
     **Note: the output of many spectrophotometers in kinetic mode is in mOD.
     ***Using the pathlength correction of 0.32 cm

Per Well:
  • rhP4HB: 0.0015 mg
  • Insulin: 0.100 mg
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: Protein Disulfide Isomerase/P4HB

Protein Disulfide Isomerase, also known as prolyl 4‑hydroxylase subunit beta (P4HB), protocollagen hydroxylase, cellular thyroid hormone binding protein p55 and glutathione-insulin transhydrogenase (1-3) is an abundant multifunctional enzyme that belongs to the Protein Disulfide Isomerase family. It contains two thioredoxin domains that catalyze the formation, breakage and rearrangement of disulfide bonds. When present as a tetramer consisting of two alpha subunits and two beta subunits, this enzyme functions as a hydroxylase catalyzing the hydroxylation of prolyl residues in preprocollagen. P4HB has various additional functions (4-7). It binds thyroid hormone. It acts as a chaperone that inhibits aggregation of misfolded proteins. It plays a role in both the influx and efflux of S-nitrosothiol-bound nitric oxide. It is also a subunit of the microsomal triglyceride transfer protein complex.

  1. Pihlajaniemi, T. et al. (1987) EMBO J. 6:643.
  2. Cheng, S.Y. et al. (1987) J. Biol. Chem. 262:11221.
  3. Morris, J. I. and Varandani, P. T. (1988) Biochim. Biophys. Acta 949:169.
  4. Obata, T. et al. (1988) J. Biol. Chem. 263:782.
  5. Gilbert, H. F. (1997) J. Biol. Chem. 272:29399.
  6. Sliskovic, I. et al. (2005) J. Biol. Chem. 280:8733.
  7. Wetterau, J. R. et al. (1990) J. Biol. Chem. 265:9800.
Long Name
Proline 4-Hydroxylase, Beta Polypeptide
Entrez Gene IDs
5034 (Human); 18453 (Mouse); 25506 (Rat)
Alternate Names
Cellular thyroid hormone-binding protein; collagen prolyl 4-hydroxylase beta; DSI; ERBA2L; GIT; glutathione-insulin transhydrogenase; P4HB; P4Hbeta; p55; PDI; PDIA1; PDIA1procollagen-proline, 2-oxoglutarate 4-dioxygenase (proline 4-hydroxylase), betapolypeptide (protein disulfide isomerase-associated 1); PDIEC; PHDB; PO4DB; PO4HB; procollagen-proline, 2-oxoglutarate 4-dioxygenase (proline 4-hydroxylase), betapolypeptide; PROHB; PROHBprocollagen-proline, 2-oxoglutarate 4-dioxygenase (proline 4-hydroxylase), betapolypeptide (protein disulfide isomerase; thyroid hormone binding protein p55); Prolyl 4-hydroxylase subunit beta; prolyl 4-hydroxylase, beta polypeptide; protein disulfide isomerase family A, member 1; protein disulfide isomerase/oxidoreductase; protein disulfide isomerase-associated 1; protein disulfide-isomerase; protocollagen hydroxylase; Thbp; thyroid hormone-binding protein p55


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