Ligase vs Lyase vs Hydrolase vs Transferase: How to Tell Them Apart

To classify an enzyme, ask three questions about its reaction. Is water used to break a bond? Then it is a hydrolase. Is a group moved from one molecule to another? Then it is a transferase. Are two molecules being joined using ATP? Then it is a ligase. Is a bond being broken or made without water, ATP or electron transfer, often leaving a double bond? Then it is a lyase.

Decision table

Hydrolase versus lyase

Both break bonds. A hydrolase adds water across the bond it breaks. A lyase breaks the bond another way, commonly leaving a double bond or a ring. Fumarase adds water to fumarate to make malate, which looks hydrolytic, but it is classed as a lyase (a hydratase) because water is added across a double bond, not used to cleave a single bond into two fragments.

Lyase versus ligase

Lyases usually act in the direction that splits a molecule, and are named -lyase, synthase (no ATP) or decarboxylase. Ligases are named -ligase or synthetase (needs ATP). A common naming convention: synthase = no ATP (a lyase), synthetase = ATP (a ligase).

Transferase versus ligase

Both can involve ATP. A kinase is a transferase because it moves the phosphate from ATP onto a substrate. A ligase uses the energy of ATP to join two substrates, and the two substrates end up bonded to each other.

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Worked examples

1. Trypsin cleaves a peptide bond using water. Hydrolase.
2. Aminotransferase moves an amino group from alanine to alpha-ketoglutarate. Transferase.
3. Aldolase splits fructose 1,6-bisphosphate into two three-carbon pieces. Lyase.
4. DNA ligase seals a nick in the backbone using ATP or NAD⁺. Ligase.

Common traps

• Calling every bond-breaking enzyme a hydrolase. It needs water.
• Calling every enzyme that uses ATP a ligase. Kinases are transferases.
• Mixing synthase and synthetase. The "t" signals ATP.
• Ignoring the names. Kinase, phosphatase, protease and ligase are strong clues.

One-minute recap

• Water cleaves: hydrolase (EC 3).
• Group moves: transferase (EC 2).
• Splits or forms bonds without water or ATP: lyase (EC 4).
• Joins with ATP: ligase (EC 6).