Which enzyme class catalyzes the joining of two substrate molecules?

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Multiple Choice

Which enzyme class catalyzes the joining of two substrate molecules?

Joining two separate molecules by forming a new covalent bond is the job of ligases. These enzymes drive bond formation between substrates, usually using energy from ATP or another triphosphate to push the reaction forward. A classic example is DNA ligase, which links adjacent DNA fragments by forming phosphodiester bonds to seal nicks in the sugar-phosphate backbone. Another example is aminoacyl-tRNA synthetase, which ligates an amino acid to its tRNA in preparation for protein synthesis. In contrast, hydrolases cleave bonds using water, lyases break or form bonds without hydrolysis or oxidation, and isomerases rearrange atoms within a single molecule. Therefore, the enzyme class that catalyzes the joining of two substrates is ligases.

Joining two separate molecules by forming a new covalent bond is the job of ligases. These enzymes drive bond formation between substrates, usually using energy from ATP or another triphosphate to push the reaction forward. A classic example is DNA ligase, which links adjacent DNA fragments by forming phosphodiester bonds to seal nicks in the sugar-phosphate backbone. Another example is aminoacyl-tRNA synthetase, which ligates an amino acid to its tRNA in preparation for protein synthesis. In contrast, hydrolases cleave bonds using water, lyases break or form bonds without hydrolysis or oxidation, and isomerases rearrange atoms within a single molecule. Therefore, the enzyme class that catalyzes the joining of two substrates is ligases.

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