Recombinant Human Thymidine Kinase 1 Protein, CF

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R&D Systems Recombinant Proteins and Enzymes
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Recombinant Human Thymidine Kinase 1 Protein, CF Summary

Product Specifications

>80%, by SDS-PAGE under reducing conditions and visualized by Colloidal Coomassie® Blue stain at 5 μg per lane
Endotoxin Level
<0.1 EU per 1 μg of the protein by the LAL method.
Measured by its ability to phosphorylate thymidine. The specific activity is >550 pmol/min/μg, as measured under the described conditions.
E. coli-derived human Thymidine Kinase 1 protein
Ser2-Asn234, with C-terminal 6-His tag
Accession #
N-terminal Sequence
Ser2 & Cys3
Predicted Molecular Mass
26 kDa
25-30 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, Glycerol, Brij-30 and DTT.
Shipping The product is shipped with dry ice or equivalent. 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, -70 °C as supplied.
  • 3 months, -70 °C under sterile conditions after opening.

Assay Procedure

  • Universal Kinase Activity Kit (Catalog # EA004)
  • 10X Assay Buffer  (supplied in kit): 250 mM HEPES, 1500 mM NaCl, 100 mM MgCl2, 100 mM CaCl2 pH 7.0
  • Recombinant Human Thymidine Kinase 1 (rhTK-1) (Catalog # 8180-TK)
  • Acceptor substrate: Thymidine (Sigma, Catalog # T9250), 100 mM stock in deionized water
  • 96-well Clear Plate (Catalog # DY990)
  • Plate Reader (Model: SpectraMax Plus by Molecular Devices) or equivalent
  1. Prepare 1X Assay Buffer containing 0.5 mM DTT.
  2. Dilute 1 mM Phosphate Standard provided by the Universal Kinase Activity Kit by adding 40 µL of the 1 mM Phosphate Standard to 360 µL of Assay Buffer for a 100 µM stock. This is the first point of the standard curve.
  3. Prepare standard curve by performing six one-half serial dilutions of the 100 µM Phosphate stock in Assay Buffer. The standard curve has a range of 0.078 to 5 nmol per well.
  4. Prepare a substrate mixture containing 0.5 mM ATP and 12.5 mM Thymidine in Assay Buffer.
  5. Dilute Coupling Phosphatase 4 (supplied in kit) to 10 µg/mL in Assay Buffer.
  6. Dilute rhTK-1 to 25 µg/mL in Assay Buffer.
  7. Load 50 µL of each dilution of the standard curve into a plate. Include a curve blank containing 50 μL of Assay Buffer.
  8. Load 20 µL of the 25 µg/mL rhTK-1 into the plate. Include a Control containing 20 µL of Assay Buffer.
  9. Add 10 µL of 10 µg/mL Coupling Phosphatase 4 to the wells, excluding the standard curve.
  10. Add 20 µL of substrate mixture to the wells, excluding the standard curve.
  11. Cover the plate with a plate sealer and incubate at room temperature for 10 minutes.
  12. Add 30 µL of Malachite Green Reagent A to all wells. Mix briefly.
  13. Add 100 µL of deionized water to all wells. Mix briefly.
  14. Add 30 µL of Malachite Green Reagent B to all wells. Mix and incubate for 20 minutes at room temperature.
  15. Read plate at 620 nm (absorbance) in endpoint mode.
  16. Calculate specific activity:

     Specific Activity (pmol/min/µg) =

Adjusted phosphate released* (nmol) x (1000 pmol/nmol)
Incubation time (min) x amount of enzyme (µg) x coupling rate**

     *Derived from the phosphate standard curve using linear fitting and adjusted for Control.

      ** The coupling rate is 0.475 under these conditions.

Per Reaction:
  • rhTK-1: 0.5 µg
  • Coupling Phosphatase 4: 0.1 μg
  • ATP: 10 nmol (0.2 mM)
  • Thymidine: 250 nmol (5 mM)
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: Thymidine Kinase 1

Thymidine kinases are 2'-deoxythymidine kinases that phosphorylate deoxythymidine and generate deoxythymidine 5’-phosphate (1). Thymidine kinases have a key function in the synthesis of DNA and thereby in cell division, as they are part of the unique reaction chain to introduce deoxythymidine into the DNA. Two forms of thymidine kinase are present in mammalian cells, TK1 and TK2. TK1 is cell cycle-dependent and is present in the cytoplasm only in anticipation of cell division (2, 3); whereas TK2 is located in mitochondria and is cell cycle-independent (4). TK1 is synthesized by the cell during the S phase of cell division and is degraded after cell division is completed (5). TK1 normally occurs in tissue as a dimer and can be converted to more active tetrameric form by ATP binding (6). TK1 is feedback inhibited by thymidine triphosphate, the product of the further phosphorylation of thymidine (7). Because tumor cells replicate much more frequently than normal cells and requires faster DNA synthesis and higher TK1 activity, TK1 is a cancer maker especially for hematologic malignancies (8, 9). In clinical chemistry TK1 is used as a proliferation marker in the diagnosis, control of treatment and follow-up of malignant disease (10). In addition, thymidine kinase is required for the action of many antiviral drugs (11). The enzymatic activity of recombinant human TK1 is measured using a phosphatase-coupled method (12).

  1. Wintersberger, E. (1997) Biochem. Soc. Trans. 25:303.
  2. Littelfield, J.W. (1966) Biochim. Biophys. Acta 114:398.
  3. Flemington, E, et al. (1987) Gene 52:267.
  4. Berk, A.J. et al. (1973) Arch. Biochem. Biophys. 154:563.
  5. Zhu, C. et al. (2006) Nucleosides Nucleotides Nucleic Acids 25:1185.
  6. Munch-Petersen, B. et al. (1993) J. Biol. Chem. 268:15621.
  7. Mikkelsen, N. E. et al. (2003). Biochemistry 42:5706.
  8. Doi S, et al. (1990) Nagoya J. Med. Sci. 52:19.
  9. Ellims PH, et al. (1981). Cancer Res. 41: 691.
  10. Lin TS, et al. (1976) J. Med. Chem.19:495.
  11. Baba M, et al. (1987). Biochem. Biophys. Res. Commun. 142:128.
  12. Wu, Z.L. (2011) PLoS One 6:e23172.
Entrez Gene IDs
7083 (Human); 21877 (Mouse)
Alternate Names
EC; thymidine kinase 1 soluble isoform; Thymidine Kinase 1; thymidine kinase 1, soluble; thymidine kinase, cytosolic; thymidine kinase-1; TK1; TK2

Citation for Recombinant Human Thymidine Kinase 1 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.

1 Citation: Showing 1 - 1

  1. CDA directs metabolism of epigenetic nucleosides revealing a therapeutic window in cancer.
    Authors: Zauri M, Berridge G, Thezenas M, Pugh K, Goldin R, Kessler B, Kriaucionis S
    Nature, 2015;524(7563):114-8.
    Species: N/A
    Sample Types: Complex Sample Type
    Applications: Enzyme Assay


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