This list contains a list of Enzyme Commission number, EC numbers for the sixth group, EC 6, ligases, placed in numerical order as determined by the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology. All official information is tabulated at the website of the committee. The database is developed and maintained by Andrew McDonald.

EC 6.1: Forming Carbon-Oxygen Bonds

EC 6.1.1: Ligases Forming Aminoacyl-tRNA and Related Compounds (Aminoacyl tRNA synthetase)

* : tyrosine-tRNA ligase, tyrosine—tRNA ligase * : tryptophan-tRNA ligase, tryptophan—tRNA ligase * : threonine-tRNA ligase, threonine—tRNA ligase * : leucine-tRNA ligase, leucine—tRNA ligase * : isoleucine-tRNA ligase, isoleucine—tRNA ligase * : lysine-tRNA ligase, lysine—tRNA ligase * : alanine-tRNA ligase, alanine—tRNA ligase * : Deleted * : valine-tRNA ligase, valine—tRNA ligase * : methionine-tRNA ligase, methionine—tRNA ligase * : serine-tRNA ligase, serine—tRNA ligase * : aspartate-tRNA ligase, aspartate—tRNA ligase * : D-alanine-poly(phosphoribitol) ligase, D-alanine—poly(phosphoribitol) ligase * : glycine-tRNA ligase, glycine—tRNA ligase * : proline-tRNA ligase, proline—tRNA ligase * : cysteine-tRNA ligase, cysteine—tRNA ligase * : glutamate-tRNA ligase, glutamate—tRNA ligase * : glutamine-tRNA ligase, glutamine—tRNA ligase * : arginine-tRNA ligase, arginine—tRNA ligase * : phenylalanine-tRNA ligase, phenylalanine—tRNA ligase * : histidine-tRNA ligase, histidine—tRNA ligase * : asparagine-tRNA ligase, asparagine—tRNA ligase * : aspartate-tRNAAsn ligase, aspartate—tRNA^Asn ligase * : glutamate-tRNAGln ligase, glutamate—tRNA^Gln ligase * EC 6.1.1.25: The tRNA^Pyl is now known only to be charged with pyrrolysine (cf. ) * : pyrrolysine—tRNAPyl ligase, pyrrolysine—tRNA^Pyl ligase * : O-phospho-L-serine—tRNA ligase, ''O''-phospho-L-serine—tRNA ligase * EC 6.1.1.28: proline/cysteine—tRNA ligase. Later published work having demonstrated that this was not a genuine enzyme, EC 6.1.1.28 was withdrawn at the public-review stage before being made official

EC 6.1.2: Acid—alcohol ligases (ester synthases)

* : D-alanine—(R)-lactate ligase, D-alanine—(''R'')-lactate ligase * : nebramycin 5′ synthase * : * No Wikipedia article

EC 6.1.3: Cyclo-ligases

* : olefin β-lactone synthetase * : * No Wikipedia article

EC 6.2: Forming Carbon-Sulfur Bonds

EC 6.2.1: Acid-Thiol Ligases

* : acetate-CoA ligase, acetate—CoA ligase * : butyrate-CoA ligase, medium-chain acyl-CoA ligase * : long-chain-fatty-acid-CoA ligase, long-chain-fatty-acid—CoA ligase * : succinate-CoA ligase (GDP-forming), succinate—CoA ligase (GDP-forming) * : succinate-CoA ligase (ADP-forming), succinate—CoA ligase (ADP-forming) * : glutarate-CoA ligase, glutarate—CoA ligase * : cholate-CoA ligase, cholate—CoA ligase * : oxalate-CoA ligase, oxalate—CoA ligase * : malate-CoA ligase, malate—CoA ligase * : acid-CoA ligase (GDP-forming), carboxylic acid—CoA ligase (GDP-forming) * : biotin-CoA ligase, biotin—CoA ligase * : 4-coumarate-CoA ligase, 4-coumarate—CoA ligase * : acetate-CoA ligase (ADP-forming), acetate—CoA ligase (ADP-forming) * : 6-carboxyhexanoate-CoA ligase, 6-carboxyhexanoate—CoA ligase * : arachidonate-CoA ligase, arachidonate—CoA ligase * : acetoacetate-CoA ligase, acetoacetate—CoA ligase * : propionate-CoA ligase, propionate—CoA ligase * : citrate-CoA ligase, citrate—CoA ligase * : long-chain-fatty-acid-luciferin-component ligase, long-chain-fatty-acid—protein ligase * : long-chain-fatty-acid-(acyl-carrier-protein) ligase, long-chain-fatty-acid—[acyl-carrier-protein] ligase * EC 6.2.1.21: Activity covered by , phenylacetate—CoA ligase * : (citrate (pro-3S)-lyase) ligase, [citrate (''pro''-3''S'')-lyase] ligase * : dicarboxylate-CoA ligase, dicarboxylate—CoA ligase * : phytanate-CoA ligase, phytanate—CoA ligase * : benzoate-CoA ligase, benzoate—CoA ligase * : o-succinylbenzoate-CoA ligase, ''o''-succinylbenzoate—CoA ligase * : 4-hydroxybenzoate-CoA ligase, 4-hydroxybenzoate—CoA ligase * : 3a,7a-dihydroxy-5b-cholestanate-CoA ligase, 3α,7α-dihydroxy-5β-cholestanate—CoA ligase * EC 6.2.1.29: Deleted, identical to , cholate—CoA ligase * : phenylacetate-CoA ligase, phenylacetate—CoA ligase * : 2-furoate-CoA ligase, 2-furoate—CoA ligase * : anthranilate-CoA ligase, anthranilate—CoA ligase * : 4-chlorobenzoate-CoA ligase, 4-chlorobenzoate—CoA ligase * : trans-feruloyl-CoA synthase, ''trans''-feruloyl-CoA synthase * : ACP-SH:acetate ligase, acetate—[acyl-carrier protein] ligase * : 3-hydroxypropionyl-CoA synthase * : 3-hydroxybenzoate—CoA ligase * : (2,2,3-trimethyl-5-oxocyclopent-3-enyl)acetyl-CoA synthase * : (butirosin acyl-carrier protein)—L-glutamate ligase, [butirosin acyl-carrier protein]—L-glutamate ligase * : 4-hydroxybutyrate—CoA ligase (AMP-forming) * * : 3-[(3aS,4S,7aS)-7a-methyl-1,5-dioxo-octahydro-1''H''-inden-4-yl]propanoate—CoA ligase * * : 3-oxocholest-4-en-26-oate—CoA ligase * * : 2-hydroxy-7-methoxy-5-methyl-1-naphthoate—CoA ligase * * : 3-(methylthio)propionyl—CoA ligase * * : E1 ubiquitin-activating enzyme * * : L-''allo''-isoleucine—holo-[CmaA peptidyl-carrier protein] ligase * * : medium-chain-fatty-acid—[acyl-carrier-protein] ligase * * : carnitine—CoA ligase * * : long-chain fatty acid adenylyltransferase FadD28 * * : 4-hydroxybenzoate adenylyltransferase FadD22 * * : 4-hydroxyphenylalkanoate adenylyltransferase FadD29 * * : L-firefly luciferin—CoA ligase * * : L-proline—[L-prolyl-carrier protein] ligase * * : D-alanine—[D-alanyl-carrier protein] ligase * * : E1 SAMP-activating enzyme * * : 4-hydroxybutyrate—CoA ligase (ADP-forming) * * : long-chain fatty acid adenylase/transferase FadD23 * * : isophthalate—CoA ligase * * : long-chain fatty acid adenylase/transferase FadD26 * * : marinolic acid—CoA ligase * * : salicylate—[aryl-carrier protein] ligase * * : 3,4-dihydroxybenzoate—[aryl-carrier protein] ligase * * : L-arginine—[L-arginyl-carrier protein] ligase * * : E1 NEDD8-activating enzyme * * : salicylate—CoA ligase * * : glyine—[glycyl-carrier protein] ligase * * : L-alanine—[L-alanyl-carrier protein] ligase * * : L-glutamate—[L-glutamyl-carrier protein] ligase * * : L-cysteine—[L-cysteinyl-carrier protein] ligase * * : L-threonine—[L-threonyl-carrier protein] ligase * * : 2,3-dihydroxybenzoate—[aryl-carrier protein] ligase * * : L-serine—[L-seryl-carrier protein] ligase * * : L-tryptophan—[L-tryptophyl-carrier protein] ligase * * : 3-amino-5-hydroxybenzoate—[acyl-carrier protein] ligase * + : indoleacetate—CoA ligase : * No Wikipedia article

EC 6.2.2: Amide—thiol ligases

* : thioglycine synthase * * : oxazoline synthase * * : thiazoline synthase * : * No Wikipedia article

EC 6.3: Forming Carbon-Nitrogen Bonds

EC 6.3.1: Acid—Ammonia (or Amine) Ligases (Amide Synthases)

* : aspartate-ammonia ligase, aspartate—ammonia ligase * : glutamate-ammonia ligase, glutamine synthetase * : Now , phosphoribosylamine—glycine ligase * : aspartate-ammonia ligase (ADP-forming), aspartate—ammonia ligase (ADP-forming) * : NAD+ synthase, NAD⁺ synthase * : glutamate-ethylamine ligase, glutamate—ethylamine ligase * : 4-methyleneglutamate-ammonia ligase, 4-methyleneglutamate—ammonia ligase * : glutathionylspermidine synthase * : trypanothione synthase * : adenosylcobinamide-phosphate synthase * : glutamate-putrescine ligase, glutamate—putrescine ligase * : D-aspartate ligase, D-aspartate ligase * : L-cysteine:1D-myo-inositol 2-amino-2-deoxy-alpha-D-glucopyranoside ligase, L-cysteine:1D-''myo''-inositol 2-amino-2-deoxy-α-D-glucopyranoside ligase * : diphthine—ammonia ligase * : 8-demethylnovobiocic acid synthase * * EC 6.3.1.16: The enzyme was discovered at the public-review stage to have been misclassified and so was withdrawn. See , carbapenam-3-carboxylate synthase * : β-citrylglutamate synthase * * : γ-glutamylanilide synthase * * : prokaryotic ubiquitin-like protein ligase * * : lipoate—protein ligase * * : phosphoribosylglycinamide formyltransferase 2 * : * No Wikipedia article

EC 6.3.2: Acid—Amino-Acid Ligases (Peptide Synthases)

* : pantoate-b-alanine ligase, pantoate—β-alanine ligase (AMP-forming) * : glutamate-cysteine ligase, glutamate—cysteine ligase * : glutathione synthase * : D-alanine-D-alanine ligase, D-alanine—D-alanine ligase * : phosphopantothenate-cysteine ligase, phosphopantothenate—cysteine ligase (CTP) * : phosphoribosylaminoimidazolesuccinocarboxamide synthase * : UDP-N-acetylmuramoyl-L-alanyl-D-glutamate-L-lysine ligase, UDP-''N''-acetylmuramoyl-L-alanyl-D-glutamate—L-lysine ligase * : UDP-N-acetylmuramate-L-alanine ligase, UDP-''N''-acetylmuramate—L-alanine ligase * : UDP-N-acetylmuramoylalanine-D-glutamate ligase, UDP-''N''-acetylmuramoyl-L-alanine—D-glutamate ligase * : UDP-N-acetylmuramoylalanyl-tripeptide-D-alanyl-D-alanine ligase, UDP-''N''-acetylmuramoyl-tripeptide—D-alanyl-D-alanine ligase * : carnosine synthase * : dihydrofolate synthase * : UDP-N-acetylmuramoylalanyl-D-glutamate-2,6-diamino-pimelate ligase, UDP-''N''-acetylmuramoyl-L-alanyl-D-glutamate—2,6-diaminopimelate ligase * : 2,3-dihydroxybenzoate-serine ligase, enterobactin synthase * EC 6.3.2.15: Deleted, The activity observed is due to , UDP-''N''-acetylmuramoyl-tripeptideD-alanyl-D-alanine ligase * : D-alanine-alanyl-poly(glycerolphosphate) ligase, D-alanine—alanyl-poly(glycerolphosphate) ligase * : tetrahydrofolate synthase * : g-glutamylhistamine synthase, γ-glutamylhistamine synthase * EC 6.3.2.19: The ubiquitinylation process is now known to be performed by several enzymes in sequence, starting with (ubiquitin-activating enzyme E1) and followed by several transfer reactions, including those of (E2 ubiquitin-conjugating enzyme) and (RING-type E3 ubiquitin transferase) * : indoleacetate-lysine synthetase, indoleacetate—lysine synthetase * EC 6.3.2.21: The reaction is performed by the sequential action of (ubiquitin-activating enzyme E1), several ubiquitin transferases and finally by [ubiquitin transferase RING E3 (calmodulin-selective)] * EC 6.3.2.22: Now , diphthine—ammonia ligase. * : homoglutathione synthase * : tyrosine-arginine ligase, tyrosine—arginine ligase * : tubulin-tyrosine ligase, tubulin—tyrosine ligase * : N-(5-amino-5-carboxypentanoyl)-L-cysteinyl-D-valine synthase, ''N''-(5-amino-5-carboxypentanoyl)-L-cysteinyl-D-valine synthase * EC 6.3.2.27: The activity is covered by two independent enzymes, ''N''²-citryl-''N''⁶-acetyl-''N''⁶-hydroxylysine synthase, and , aerobactin synthase * EC 6.3.2.28: Now , L-alanine-L-anticapsin ligase * : cyanophycin synthase (L-aspartate-adding), cyanophycin synthase (L-aspartate-adding) * : cyanophycin synthase (L-arginine-adding), cyanophycin synthase (L-arginine-adding) * : coenzyme F420-0:L-glutamate ligase, coenzyme F₄₂₀-0:L-glutamate ligase * : coenzyme gamma-F420-2:alpha-L-glutamate ligase, coenzyme γ-F₄₂₀-2:α-L-glutamate ligase * : tetrahydrosarcinapterin synthase * : coenzyme F420-1:gamma-L-glutamate ligase, coenzyme F₄₂₀-0:L-glutamate ligase * : D-alanine---D-serine ligase, D-alanine—D-serine ligase * : 4-phosphopantoate---beta-alanine ligase, 4-phosphopantoate—β-alanine ligase * : UDP-N-acetylmuramoyl-L-alanyl-D-glutamate---D-lysine ligase, UDP-N-acetylmuramoyl-L-alanyl-D-glutamate—D-lysine ligase * : N2-citryl-N6-acetyl-N6-hydroxylysine synthase, ''N''²-citryl-''N''⁶-acetyl-''N''⁶-hydroxylysine synthase * : aerobactin synthase * : cyclopeptine synthase * * : ''N''-acetylaspartylglutamate synthase * * : synthase * * : [amino-group carrier protein]—L-2-aminoadipate ligase * * : pantoate—β-alanine ligase (ADP-forming) * * : UDP-''N''-acetylmuramate—L-alanyl-γ-D-glutamyl-meso-2,6-diaminoheptanedioate ligase * * : fumarate—(''S'')-2,3-diaminopropanoate ligase * * : dapdiamide synthase * * : L-arginine-specific L-amino acid ligase * * : L-alanine—L-anticapsin ligase * * : tenuazonic acid synthetase * * : phosphopantothenate—cysteine ligase (ATP) * * : jasmonoyl—L-amino acid ligase * * : UDP-''N''-acetylmuramoyl-L-alanine—L-glutamate ligase * * : L-2,3-diaminopropanoate—citrate ligase * * : 2-[(L-alanin-3-ylcarbamoyl)methyl]-3-(2-aminoethylcarbamoyl)-2-hydroxypropanoate synthase * * : staphyloferrin B synthase * * : staphyloferrin A synthase * * : D-ornithine—citrate ligase * * : 3-methyl-D-ornithine—L-lysine ligase * * : glutamate—[amino group carrier protein] ligase * * : tubulin-glutamate ligase * * : β-tubulin-glutamate ligase * : * No Wikipedia article

EC 6.3.3: Cyclo-Ligases

* : phosphoribosylformylglycinamidine cyclo-ligase * : 5-formyltetrahydrofolate cyclo-ligase * : dethiobiotin synthase * : (carboxyethyl)arginine b-lactam-synthase, (carboxyethyl)arginine β-lactam-synthase * : ''O''-ureido-D-serine cyclo-ligase * * : carbapenam-3-carboxylate synthase * * : Ni-sirohydrochlorin ''a,c''-diamide reductive cyclase * : * No Wikipedia article

EC 6.3.4: Other Carbon-Nitrogen Ligases

* EC 6.3.4.1: Now included in , GMP synthase (glutamine-hydrolysing) * : CTP synthase, CTP synthase (glutamine hydrolysing) * : formate-tetrahydrofolate ligase, formate—tetrahydrofolate ligase * : adenylosuccinate synthase * : argininosuccinate synthase * : urea carboxylase * : ribose-5-phosphate-ammonia ligase, ribose-5-phosphate—ammonia ligase * : imidazoleacetate-phosphoribosyldiphosphate ligase, imidazoleacetate—phosphoribosyldiphosphate ligase * : biotin-(methylmalonyl-CoA-carboxytransferase) ligase, biotin—[methylmalonyl-CoA-carboxytransferase] ligase * : biotin-(propionyl-CoA-carboxylase (ATP-hydrolysing)) ligase, biotin—[methylmalonyl-CoA-carboxytransferase] ligase * : biotin-(methylcrotonoyl-CoA-carboxylase) ligase, biotin—[methylcrotonoyl-CoA-carboxylase] ligase * : glutamate-methylamine ligase, glutamate—methylamine ligase * : phosphoribosylamine-glycine ligase, phosphoribosylamine—glycine ligase * : biotin carboxylase * : biotin-(acetyl-CoA-carboxylase) ligase, biotin—[biotin carboxyl-carrier protein] ligase * : carbamoyl-phosphate synthase (ammonia) * : formate-dihydrofolate ligase, formate—dihydrofolate ligase * : 5-(carboxyamino)imidazole ribonucleotide synthase * : tRNAIle-lysidine synthase, tRNA^Ile-lysidine synthase * : 7-cyano-7-deazaguanine synthase * : nicotinate phosphoribosyltransferase * : tRNA^Ile2-agmatinylcytidine synthase * * : formate—phosphoribosylaminoimidazolecarboxamide ligase * * : tyramine—L-glutamate ligase * * : 2-amino-2′-deoxyadenylo-succinate synthase * : * No Wikipedia article

EC 6.3.5: Carbon-nitrogen ligases with glutamine as amido-''N''-donor

* : NAD+ synthase (glutamine-hydrolysing), NAD⁺ synthase (glutamine-hydrolysing) * : GMP synthase (glutamine-hydrolysing) * : phosphoribosylformylglycinamidine synthase * : asparagine synthase (glutamine-hydrolysing) * : carbamoyl-phosphate synthase (glutamine-hydrolysing) * : asparaginyl-tRNA synthase (glutamine-hydrolysing) * : glutaminyl-tRNA synthase (glutamine-hydrolysing) * EC 6.3.5.8: Now , aminodeoxychorismate synthase. As ATP is not hydrolysed during the reaction, the classification of the enzyme as a ligase was incorrect * : hydrogenobyrinic acid a,c-diamide synthase (glutamine-hydrolysing), hydrogenobyrinic acid ''a,c''-diamide synthase (glutamine-hydrolysing) * : adenosylcobyric acid synthase (glutamine-hydrolysing) * : cobyrinate a,c-diamide synthase, cobyrinate ''a,c''-diamide synthase * : Ni-sirohydrochlorin ''a,c''-diamide synthase * * : lipid II isoglutaminyl synthase (glutamine-hydrolysing) * : * No Wikipedia article

EC 6.4: Forming Carbon-Carbon Bonds

EC 6.4.1: Ligases that form carbon-carbon bonds (only sub-subclass identified to date)

* : pyruvate carboxylase * : acetyl-CoA carboxylase * : propionyl-CoA carboxylase * : methylcrotonoyl-CoA carboxylase * : geranoyl-CoA carboxylase * : acetone carboxylase * : 2-oxoglutarate carboxylase * : acetophenone carboxylase * : coenzyme F₄₃₀ synthetase * : *No Wikipedia article

EC 6.5: Forming Phosphoric Ester Bonds

EC 6.5.1: Ligases that form phosphoric-ester bonds (only sub-subclass identified to date)

* : DNA ligase (ATP) * : DNA ligase (NAD+), DNA ligase (NAD⁺) * : RNA ligase (ATP) * : RNA-3'-phosphate cyclase, RNA 3′-terminal-phosphate cyclase (ATP) * : RNA 3′-terminal-phosphate cyclase (GTP) * * : DNA ligase (ATP or NAD⁺) * * : DNA ligase (ATP, ADP or GTP) * * : 3′-phosphate/5′-hydroxy nucleic acid ligase * * : cyclic 2,3-diphosphoglycerate synthase * : * No Wikipedia article