Here's why:

* Enzymes are biological catalysts, meaning they speed up chemical reactions in living organisms.

* Proteins are complex molecules with a wide variety of shapes and functions. This unique structure allows proteins to act as enzymes by providing specific binding sites for reactants (substrates).

* Carbohydrates, lipids, and nucleic acids have different structures and functions. While they are essential for life, they don't typically act as catalysts in the same way that enzymes do.

Let me know if you'd like to learn more about enzymes or proteins!