Lactase catalyzes the hydrolysis of lactose, a disaccharide sugar found in milk, into glucose and galactose, which are monosaccharides.

Here's the chemical equation:

Lactose + H₂O → Glucose + Galactose

In this reaction, lactase acts as an enzyme, speeding up the process of breaking down lactose into simpler sugars that the body can absorb and use for energy.