Lipids are not enzymes, or to put it in another way enzymes are protein in nature and not lipids, nucleic acids or carbohydrates. Enzymes are defined as organic substances which speed up biochemical reactions but they remain exactly the way they were before and after the reaction, that is they are not changed, before, during and after the reaction.
Enzymes are a special kind of protein and they exhibit protein characteristics. One of the main characteristics is that they are affected by extreme pH and temperature. When exposed to such, they get denatured. Protein is the only macromolecule that gets denatured and become inactive or damaged permanently
Enzymes work best within a narrow pH and temperature range specific to each enzyme, outside of which they are rendered inactive.
