Alanine-tRNA Ligase: An enzyme that activates alanine with its specific transfer RNA. EC 18.104.22.168.RNA Ligase (ATP): An enzyme that catalyzes the conversion of linear RNA to a circular form by the transfer of the 5'-phosphate to the 3'-hydroxyl terminus. It also catalyzes the covalent joining of two polyribonucleotides in phosphodiester linkage. EC 22.214.171.124.Ubiquitin-Protein Ligases: A diverse class of enzymes that interact with UBIQUITIN-CONJUGATING ENZYMES and ubiquitination-specific protein substrates. Each member of this enzyme group has its own distinct specificity for a substrate and ubiquitin-conjugating enzyme. Ubiquitin-protein ligases exist as both monomeric proteins multiprotein complexes.DNA Ligases: Poly(deoxyribonucleotide):poly(deoxyribonucleotide)ligases. Enzymes that catalyze the joining of preformed deoxyribonucleotides in phosphodiester linkage during genetic processes during repair of a single-stranded break in duplex DNA. The class includes both EC 126.96.36.199 (ATP) and EC 188.8.131.52 (NAD).Polynucleotide Ligases: Catalyze the joining of preformed ribonucleotides or deoxyribonucleotides in phosphodiester linkage during genetic processes. EC 6.5.1.