Enzymes are proteins, which in turn are chains of amino acids linked by ends.
Denaturation of enzymes causes bonds to be broken, structure to be disrupted and it stops functioning.
This happens to enzymes when they are exposed to extreme, unsuitable conditions, for instance, high temperatures or extreme pH levels.
The shape of its active site changes following which the substrate does not fit into the enzymes anymore.
Subsequently, the rate of reaction is influenced causing it to either slow down or stop. Hence, for the normal functioning of enzymes, maintaining an appropriate temperature is vital.