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Specialty Chemistry Forums => Biochemistry and Chemical Biology Forum => Topic started by: distheho on January 22, 2021, 04:31:24 PM

Title: Can michaelis menton equation determine IC50
Post by: distheho on January 22, 2021, 04:31:24 PM

If I plot the % reduced (from uninhibited reaction) enzyme reaction rate vs inhibitor concentration, is the "Km" the IC50 for that specific enzyme concentration?

Title: Re: Can michaelis menton equation determine IC50
Post by: Babcock_Hall on January 23, 2021, 08:48:11 AM

I am a little puzzled by your reference to the enzyme concentration.  Can you explain?

Title: Re: Can michaelis menton equation determine IC50
Post by: distheho on January 23, 2021, 10:53:48 AM

It is my understanding that IC50 is based on enzyme concentration.

Title: Re: Can michaelis menton equation determine IC50
Post by: Babcock_Hall on January 23, 2021, 11:55:27 AM

https://pubmed.ncbi.nlm.nih.gov/4202581/
There is a 1973 paper by Cheng and Prusoff that discusses the meanings of IC50.  With respect to the Michaelis-Menten equation, K_M does not depend on enzyme concentration.  Just glancing at the paper, IC50 values do depend on substrate concentration.