and Cells

Calculate the number of (international) enzyme units in a sample from the amount of substrate converted to product per minute per ml, measured in an aliquot of the sample.

« 1 enzyme unit = the enzyme activity that catalyses the conversion of

1 µmol substrate into product in 1 minute »

1 µmol substrate into product in 1 minute »

Enzyme units:

You should aim to do these calculations in your head or on a scrap of paper (i.e. without a calculator). The following logic may be helpful:
*x* µmol per min, then the answer will be of the order of magnitude of *x*.

- Enzyme units are expressed as µmol substrate converted per min.
- If the question gives enzyme activity in nmol per min, divide by 1000 to convert to µmol.
- Then multiply by the volume to get the total number of units.
- To summarize, the total number of enzyme units is: volume x substrate conversion rate/(1000 if nmol, or 1 if µmol)