Enzyme kinetics

Benno ter Kuile b.terkuile at chem.leidenuniv.nl
Thu Sep 13 02:51:02 EST 2001

	The point is you should reason from the probability that the 
active site of the enzyme encounters a substrate molecule. That 
chance does not change as a function of the number of other 
enzyme molecules in the surrounding, but depends only on the 
substrate concentration. It is as if you titrate the enzyme with its 

Hope this clarifies it for you.


> I am having trouble understanding the MM constant Km. If the Vmax is
> decreased by a decrease in enzyme concentration, why doesn't the Km decrease
> too? I know that the Km is a constant, derived mathematically from
> equilibrium constants, but I am having trouble understanding it intuitively.
> If you have less enzyme, then wouldn't it take less substrate to reach 1/2
> Vmax?
> Also, in chemistry, is it correct to visualize ligands "binding" to enzyme
> (or anything else) as actually fluctuating between bound and unbound? Isn't
> that why, if you have a competitive inhibitor and increase substrate, the
> substrate will eventually win out and "overcome" the I--because really
> everything is constantly moving on and off and if you have more substrate
> eventually it gets on more than the inhibitor does?
> thanks for your help
> <http://www.biowww.net/forum/read.php?f=6&i=680&t=680>

Benno ter Kuile
Leiden Institute of Chemistry, Gorlaeus Laboratories.
Leiden University;Einsteinweg 55 / P.O. Box 9502 2300RA, Leiden, The Netherlands.
Phone:        +31 71 5275272    TeleFax:      +31 71 5274537


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