Working with Enzymes Supplied as Ammonium Sulfate Suspensions – Technical Note

— If the ammonium sulfate might interfere with the reaction(s):

  1. Remove the enzyme from the refrigerator. Note: We strongly recommend that ammonium sulfate suspensions not be frozen.
  2. Make sure the cap is on tight, and then invert the vial/bottle several times to provide a milky suspension. This may take a minute or so. Do not vortex or sonicate; such harsh treatment may denature some of the enzyme.
  3. Using a pipette and sterile wide-bore pipette tip, remove a portion of the suspension.
  4. Transfer to a clean microcentrifuge tube (or centrifuge tube if working on a larger scale).
  5. Pellet the enzyme by centrifuging at approximately 10,000 – 15,000 x g for 10 minutes. If available, use a refrigerated microcentrifuge set to a temperature between 2°C and 8°C.
  6. Carefully remove as much clear supernatant as possible; retain. It is not necessary to remove absolutely all of the ammonium sulfate solution.
  7. Dissolve the pellet by adding an appropriate amount of reaction buffer.
  8. Assay the supernatant, and the solution from the pellet, for protein content and/or enzyme activity.

— If the ammonium sulfate will not interfere with the reaction(s):

  1. As in steps 1-3 above.
  2. Add that portion directly to the reaction buffer.

Note that for an ammonium sulfate suspension, most of the enzyme will be in solid form. It is likely that only negligible amounts of enzyme will be in the ammonium sulfate solution.

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