From Arrhenius equation, k = Ae ^–E_a/RT

The activation energy of the reaction in the presence of enzyme is different from E_a obtained in laboratory.

$$ - {1 \over 3}$$$${{d\left[ {B{r^ - }} \right]} \over {dt}} = + {1 \over 5}{{d\left[ {B{r_2}} \right]} \over {dt}}$$

$$ \Rightarrow $$ $${{d\left[ {B{r^ - }} \right]} \over {dt}} = - {3 \over 5}{{d\left[ {B{r_2}} \right]} \over {dt}}$$

Enzymes act like catalyst in biochemical reactions. Presence of an enzyme increases the rate of reaction by lowering the activation energy of the reactant.