The reactants of an enzyme-catalyzed reaction are known as substrates.

Here's why:

* Enzymes are catalysts: They speed up chemical reactions without being consumed in the process.

* Substrates bind to enzymes: The specific molecules that an enzyme acts upon are called substrates.

* Enzymes facilitate the conversion of substrates into products: The enzyme provides an alternative reaction pathway with a lower activation energy, allowing the reaction to proceed more quickly.

So, in the context of an enzyme-catalyzed reaction, it's important to distinguish between the reactants (which are the substrates) and the enzyme itself.