Final answer:
A ligase is an enzyme that connects two substrates together using energy, often from ATP hydrolysis, which distinguishes it from other enzymes like hydrolases or kinases.
Step-by-step explanation:
An enzyme that joins two substrates using energy is referred to as a ligase. Ligases catalyze the joining of two molecules in a process that requires energy, typically from the hydrolysis of ATP.
This is in contrast to other types of enzymes such as hydrolases, which break bonds by adding water; transferases, which move functional groups from one molecule to another; and kinases, which specifically add phosphate groups to molecules.