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EC 2.8.1.8 Details
EC number
2.8.1.8
Accepted name
lipoyl synthase
Reaction
[protein]-N6-(octanoyl)-L-lysine + an [Fe-S] cluster scaffold protein carrying a [4Fe-4S]2+ cluster + 2 S-adenosyl-L-methionine + 2 oxidized [2Fe-2S] ferredoxin + 6 H+ = [protein]-N6-[(R)-dihydrolipoyl]-L-lysine + an [Fe-S] cluster scaffold protein + 2 sulfide + 4 Fe3+ + 2 L-methionine + 2 5′-deoxyadenosine + 2 reduced [2Fe-2S] ferredoxin
Other name(s)
lipA (gene name), LS, lipoate synthase, protein 6-N-(octanoyl)lysine:sulfur sulfurtransferase, protein N6-(octanoyl)lysine:sulfur sulfurtransferase, protein N6-(octanoyl)lysine:sulfur-(sulfur carrier) sulfurtransferase
Systematic name
[protein]-N6-(octanoyl)-L-lysine:an [Fe-S] cluster scaffold protein carrying a [4Fe-4S]2+ cluster sulfurtransferase
CAS registry number
189398-80-9
Comment
This enzyme catalyses the final step in the de-novo biosynthesis of the lipoyl cofactor, the attachment of two sulfhydryl groups to C6 and C8 of a pendant octanoyl chain. It is a member of the ‘AdoMet radical’ (radical SAM) family, all members of which produce the 5′-deoxyadenosin-5′-yl radical and methionine from AdoMet (S-adenosylmethionine) by the addition of an electron from an iron-sulfur centre. The enzyme contains two [4Fe-4S] clusters. The first cluster produces the radicals, which are converted into 5′-deoxyadenosine when they abstract hydrogen atoms from C6 and C8, respectively, leaving reactive radicals at these positions that interact with sulfur atoms within the second (auxiliary) cluster. Having donated two sulfur atoms, the auxiliary cluster is degraded during catalysis, but is regenerated immediately by the transfer of a new cluster from iron-sulfur cluster carrier proteins [8]. Lipoylation is essential for the function of several key enzymes involved in oxidative metabolism, as it converts apoprotein into the biologically active holoprotein. Examples of such lipoylated proteins include pyruvate dehydrogenase (E2 domain), 2-oxoglutarate dehydrogenase (E2 domain), the branched-chain 2-oxoacid dehydrogenases and the glycine cleavage system (H protein) [1,2]. An alternative lipoylation pathway involves EC 6.3.1.20, lipoate—protein ligase, which can lipoylate apoproteins using exogenous lipoic acid (or its analogues) [4].
History
created 2006, modified 2014, modified 2018
EC Tree
2.5.1.12 created 1972, deleted 1976
2.5.1.13 created 1972, deleted 1976
2.5.1.14 created 1972, deleted 1976
2.5.1.37 created 1989, deleted 2004
2.5.1.40 created 1992, deleted 1999