Recombinant Human IMP Dehydrogenase 2/IMPDH2 Protein, CF

• 6 months from date of receipt, -20 to -70 °C as supplied.
• 3 months, -20 to -70 °C under sterile conditions after opening.

• Assay Buffer: 50 mM Tris, 300 mM NaCl, 1 mM EDTA, 1 mM DTT, pH 8.0
• Recombinant Human Inosine 5'-Monophosphate Dehydrogenase 2/IMPDH2 (rhIMPDH2) (Catalog # 8349-DH)
• Nicotinamide adenine dinucleotide sodium salt ( beta -NAD) (Sigma, Catalog # N6522), 100 mM stock in deionized water
• Inosine 5'-monophosphate (IMP) (Sigma, Catalog # I4625), 100 mM stock in deionized water.
  
• UV plate (Costar, Catalog # 3635)
• Plate Reader (Model: SpectraMax Plus by Molecular Devices) or equivalent

1. Dilute rhIMPDH2 to 20 μg/mL in Assay Buffer.
2. Create Substrate Mixture containing 500 μM IMP and 1 mM beta -NAD in Assay Buffer.
3. Load 50 μL of 20 μg/mL rhIMPDH-2 into a plate, and start the reaction by adding 50 μL of Substrate Mixture. For Substrate Blanks, load 50 μL of Assay Buffer and 50 μL of Substrate Mixture.
4. Read plate at a wavelength of 339 nm (bottom read) in kinetic mode for 5 minutes.
5. Calculate specific activity:

*Adjusted for Substrate Blank.
**Using the extinction coefficient 6220 M^-1cm^-1.
***Using the path correction 0.320 cm.
Note: the output of many spectrophotometers is in mOD.

• rhIMPDH-2: 1.0 μg
• beta -NAD: 500 μM
• IMP: 250 μM