You can look at the published literature on the enzyme to see what values have been reported by others. If you use the same substrate, the same enzyme (from the same species) and run the reaction under the same conditions (temperature, pH, salts, buffer), you should be able to get a similar value.

Dear Sir Adam B Shapiro

YEs I was trying to found some published literature, but the problem is in my case, I obtained different Km value. I am using electrochemical rotating disk electrode technique for determining Km values. Is there any difference can observe from different methods?

Thank you so much for your answer.

Dear Kou Hayakawa Sensei

Thank you so much for your answer.

In my case the method is electrochemical rotating disk electrode and I want to stabilize the impacts of rotation rate on the detection by using Km values. Hence my objective is to calculate the Km values at different rotation rates with various concentrations of substrates.