How do you determine if an enzyme digested its substrate?

Answer 1

The only way to know if the enzyme has converted all of the substrate into product is to (1) measure the amount of substrate still there, or (2) remove the enzyme and add new enzyme and see if you still get product formed. If so, then the first enzyme treatment did NOT use all of the substrate. One other possible way to determine if all the substrate was used up is to know the stoichiometry between conversion of substrate to product. Then when you measure the product, you'll know if all or part of the substrate had been used.

Answer 2

Enzymes don't digest the substrate.

An enzyme is a protein that acts as a catalyst in making a certain product from the substrate.

Answer 3

You analyze the digestion product. A lot of time, you can use a chemical method to detect the product. If a reagent produces a color compound with the product, and not the substrate, you can demonstrate the enzyme activity by measuring the absorbance of the color compound with a spectrophotometer.

Answer 4

It depends on the enzyme and substrate. If you're looking at a DNAse for example (an enzyme that digests DNA) then you could run the sample on a gel and look for DNA fragmentation.

Another example could be luciferase/luciferin. Luciferase is an enzyme that cleaves luciferin in two. This releases a photon, so you know that your enzyme is working if the sample is glowing, and you'll know that the substrate is gone if the sample stops glowing.