How does the active site of an enzyme cause a High rate of reaction ...

The active site of an enzyme would form enzyme-substrate complex thus lowering the activation energy of the reaction and high rate of reaction is found.

Explanation:

The energy required to start the reaction is activation energy. In our system enzymes catalyses the reaction by lowering the activation energy. When the substrate binds to the active site or catalytic site of enzyme, an enzyme - substrate complex is formed. This complex reduces the time required for substrate changing into product. The enzyme substrate complex results in the conformational changes and contributes in lowering of activation energy.