Factors affecting enzyme activity Temperature: Raising temperature generally speeds up a reaction, and lowering temperature slows down a reaction. However, extreme high temperatures can cause an enzyme to lose its shape (denature) and stop working.
An enzyme is a protein, and proteins need certain temperatures to function optimally, or even function. Temperature may unfold the protein and may stop its functioning, or it may fold the protein into the correct formation to function. But by the way your question asks, EXCESS heat would denature the enzyme and cease function.
