Key Characteristics of Ligases:

• Ligases facilitate the establishment of covalent bonds between molecules, often harnessing energy released from ATP hydrolysis.
• Ligases play a crucial role in DNA replication and repair, sealing breaks in DNA strands' phosphodiester backbone. They also contribute to RNA synthesis.
• Ligases are vital in protein synthesis where they contribute to the formation of polypeptide chains by forming peptide bonds between amino acids. 
• Ligases demonstrate specificity towards substrates, selectively identifying and catalyzing the fusion of specific molecules. For instance, DNA ligase specifically acts on nucleic acid substrates.
• Ligation reactions, which are catalyzed by ligases, require energy input, which is typically obtained by ATP hydrolysis.