A lyase is a type of enzyme that catalyzes the breaking of chemical bonds in molecules without the addition of water, which distinguishes them from hydrolases. Instead of hydrolysis, lyases often create double bonds or rings in the process. They play a crucial role in various metabolic pathways, facilitating reactions that are essential for cellular function. Lyases are involved in the synthesis and breakdown of biomolecules, such as amino acids and nucleotides. By removing groups from substrates, they help regulate metabolic processes and contribute to the overall balance of biochemical reactions in living organisms.