Activities of Enzymes

Andreas Aemissegger aae at bluewin.ch
Tue Aug 19 20:04:40 EST 1997


On 19 Aug 1997 05:28:51 GMT, "Tham Seng Choe" <sengchoe at pobox.org.sg>
wrote:


>We understand from most books that the enzyme speeds up a reaction BUT does
>not change the equilibrium of the reaction. Assuming a general equation ...
>
>S + Enzyme(E) ---> ES-complex ---> E + P
>
>An enzyme speeds up the formation of a product by providing an alternative
>pathway with lower activation energy so that the forward reaction proceeds
>with a faster rate. However, this does not show how the corressponding
>backward reaction rate is adjusted (increased in this case) to keep the
>equilibrium of the entire reaction unchanged.
>
>Does the enzyme catalyse the backward reaction as well?

As you mention, the enzyme can't change the equilibrium of the
reaction. The equilibrium is determined thermodynamically and
therefore the reaction rate must increase in both directions.

>If so, would this
>not compromise on the "specificity" of the enzyme? And would this not
>provide a form a competitive inhibition which would decrease the efficiency
>of the enzyme?

Yes. It's called "feed-back inhibition" (or was it "product
inhibition"?) and is used to control enzymatic reactions.

Andreas
aae at bluewin.ch



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