The Enzyme Database

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EC 2.8.1.8     
Accepted name: lipoyl synthase
Reaction: protein N6-(octanoyl)lysine + 2 sulfur-(sulfur carrier) + 2 S-adenosyl-L-methionine = protein N6-(lipoyl)lysine + 2 (sulfur carrier) + 2 L-methionine + 2 5′-deoxyadenosine
Other name(s): LS; LipA; lipoate synthase; protein 6-N-(octanoyl)lysine:sulfur sulfurtransferase; protein N6-(octanoyl)lysine:sulfur sulfurtransferase
Systematic name: protein N6-(octanoyl)lysine:sulfur-(sulfur carrier) sulfurtransferase
Comments: This enzyme 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 [i.e. S-adenosylmethionine, or S-(5′-deoxyadenosin-5′-yl)methionine], by the addition of an electron from an iron-sulfur centre. The radical is converted into 5′-deoxyadenosine when it abstracts a hydrogen atom from C-6 and C-8, leaving reactive radicals at these positions so that they can add sulfur, with inversion of configuration [4]. This enzyme catalyses the final step in the de-novo biosynthesis of the lipoyl cofactor, with the other enzyme involved being EC 2.3.1.181, lipoyl(octanoyl) transferase. 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) [2,5]. An alternative lipoylation pathway involves EC 2.7.7.63, lipoate—protein ligase, which can lipoylate apoproteins using exogenous lipoic acid (or its analogues) [7].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 189398-80-9
References:
1.  Cicchillo, R.M. and Booker, S.J. Mechanistic investigations of lipoic acid biosynthesis in Escherichia coli: both sulfur atoms in lipoic acid are contributed by the same lipoyl synthase polypeptide. J. Am. Chem. Soc. 127 (2005) 2860–2861. [PMID: 15740115]
2.  Vanden Boom, T.J., Reed, K.E. and Cronan, J.E., Jr. Lipoic acid metabolism in Escherichia coli: isolation of null mutants defective in lipoic acid biosynthesis, molecular cloning and characterization of the E. coli lip locus, and identification of the lipoylated protein of the glycine cleavage system. J. Bacteriol. 173 (1991) 6411–6420. [PMID: 1655709]
3.  Zhao, X., Miller, J.R., Jiang, Y., Marletta, M.A. and Cronan, J.E. Assembly of the covalent linkage between lipoic acid and its cognate enzymes. Chem. Biol. 10 (2003) 1293–1302. [PMID: 14700636]
4.  Cicchillo, R.M., Iwig, D.F., Jones, A.D., Nesbitt, N.M., Baleanu-Gogonea, C., Souder, M.G., Tu, L. and Booker, S.J. Lipoyl synthase requires two equivalents of S-adenosyl-L-methionine to synthesize one equivalent of lipoic acid. Biochemistry 43 (2004) 6378–6386. [PMID: 15157071]
5.  Jordan, S.W. and Cronan, J.E., Jr. A new metabolic link. The acyl carrier protein of lipid synthesis donates lipoic acid to the pyruvate dehydrogenase complex in Escherichia coli and mitochondria. J. Biol. Chem. 272 (1997) 17903–17906. [PMID: 9218413]
6.  Miller, J.R., Busby, R.W., Jordan, S.W., Cheek, J., Henshaw, T.F., Ashley, G.W., Broderick, J.B., Cronan, J.E., Jr. and Marletta, M.A. Escherichia coli LipA is a lipoyl synthase: in vitro biosynthesis of lipoylated pyruvate dehydrogenase complex from octanoyl-acyl carrier protein. Biochemistry 39 (2000) 15166–15178. [PMID: 11106496]
7.  Perham, R.N. Swinging arms and swinging domains in multifunctional enzymes: catalytic machines for multistep reactions. Annu. Rev. Biochem. 69 (2000) 961–1004. [PMID: 10966480]
[EC 2.8.1.8 created 2006]
 
 


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