Regarding enzyme kinetics

Question

You are deciding which of two enzymes to buy for your Biotech company. Evaluated on the same substrate Enzyme A has a kcat of 950 s-1 and a KM of 200 μM, whereas Enzyme B has a kcat of 2500 s-1 and a KM of 400 μM.

 

a. If your application involves substrates in the range 1-10 μM, which enzyme should you buy?


b. If your application involves substrates in the range 10-100 mM, which enzyme should you buy?

Answer 1

IMHO this question is vague, because it will depend on what applications the enzyme is being use for.  If simply looking at catalytic efficiency, Enzyme B would be preferable regardless of substrate concentration.  If you are using the enzyme preparation as an analytic tool to measure the substrate, then 1-10 uM situations would best be suited to using Enzyme A, and if you have substrate concentrations in the 10-100 mM (? or is that supposed to be uM), then Enzyme B would be better.  Again, the question, IMO, is too vague for a proper answer.