Lyase

Part of speech: noun

Definitions

1. A class of enzymes that break chemical bonds by adding or removing groups without using water or oxidation, often forming double bonds in the process
2. An enzyme that splits molecules apart by cleaving a bond in a way that does not involve hydrolysis or redox reactions, such as decarboxylases and aldolases
3. A biological catalyst that severs a chemical bond in a substrate through elimination, addition, or similar mechanisms rather than by adding water

Etymology: "Lyase" is a modern scientific coinage, built from the Greek verb "lyein", meaning "to loosen" or "to dissolve," with the suffix "-ase" that chemists attach to the names of enzymes. The "-ase" ending was standardized in the late nineteenth century as a way of marking a protein that acts as a biological catalyst, so the word pairs an ancient verb for untying or breaking apart with a much newer naming convention. The name describes what these enzymes do. Many enzymes break molecules by reacting them with water, a process called hydrolysis, and those are named differently. Lyases cut bonds in other ways, removing a small group from a substrate and leaving a double bond behind, or in reverse adding a group across a double bond. The name "lyase" thus marks a whole class defined by its mechanism rather than by any single molecule, which is why the term groups together many unrelated enzymes that happen to share this non-hydrolytic style of breaking bonds.