The reactants of enzyme-catalyzed reactions are known as substrates.

Here's why:

* Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process.

* Substrates are the molecules that bind to the active site of an enzyme and undergo a chemical transformation.

* The enzyme facilitates the reaction by lowering the activation energy, allowing the substrate to be converted into products.

So, the key takeaway is that enzymes act on substrates to produce products.