Google this exact same question you’ll find many different answers
Other enzymes help bind two molecules together to produce a new molecule. Enzymes are highly selective catalysts meaning that each enzyme only speeds up a specific reaction. The molecules that an enzyme works with are called substrates. The substrates bind to a region on the enzyme called the active site.
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Another explanation could also be:
A simple explanation is that the substrate molecule(s) fits into a specific area of the enzyme molecule (active site). This forms an enzyme-substrate complex; the substrate molecule(s) is changed during its interaction with the enzyme molecule.