Enzyme Kinetics

[PharmDPotential]

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Hi everyone,

I'm not sure if this is on the PCAT but I heard you needed to know enzyme kinetics pretty well for pharm school. My question is about the Michaelis Menten eq. For Km, I understand that it is a constant that dictates an enzyme's affinity towards a substrate, and that Km = rate of the breakdown of enzyme-substrate complexes divided by the rate of enzyme-substrate formation. But when more enzyme is added, why is there no change in Km?

I'm confused bc if you add more enzyme, wouldn't there be more formation of enzyme-substrate complex?

Thank you.

 

[jerbearox]

maybe because as more enzyme is added both the rate of breakdown and the rate of formation increase by the same magnitude resulting in the same Km.

 

[Corpseman]

http://forums.studentdoctor.net/showpost.php?p=10297137&postcount=3

 

[PharmDPotential]

http://forums.studentdoctor.net/showpost.php?p=10297137&postcount=3

Yes I already read this. But I still don't get what the person said. The writer stated that,

"To understand why Km doesn't change when you add more and more enzyme, just think of
Km = (K(ES-->S+E)+K(ES-->P+E))/K(S+E-->ES).

Km is only dependent on the rate of formation of the ES, rate of dissociation of the ES complex, and the rate of formation of the product. None of that is going to change with more or less substrate. "

If you add more enzyme, doesn't the rate of formation of ES increase? Hence Km increases as well?