Allosteric Activators shift curve?

[SaintJude]

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In regards to the "reaction velocity vs. substrate curve, why do allosteric activators shift this curve for a given reaction to the left?
Allosteric activators bind to the protein at a secondary site and change the receptor's affinity to increase the protein's affinity for its substrate.

 

[lkthlttr]

I would suggest thinking about it in terms of Km. The Km is the concentration of substrate at which the initial velocity is half of Vmax. The allosteric activator increases the affinity of the enzyme for its substrate, meaning that less substrate is required to achieve a the half maximal velocity, or in other words Km is lowered. In order to achieve a curve with the same Vmax and a lower Km, the curve simply shifts to the left.

 

[gravitywave]

curve goes left, you say. left means lower Km. lower Km means higher affinity, which is just what we would expect from an activator. higher V at any given , in fact.

These graphs are vile. I have had to learn them again (for the third time) for Step 1. Once you embrace the fact that you are in reciprocal land, where everything is the opposite of what it seems, you are golden.