If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Locations of Mapped Genes:
Synonyms: S-adenosylmethionine biosynthesis
|Superclasses:||Biosynthesis → Cofactors, Prosthetic Groups, Electron Carriers Biosynthesis|
It has been said that no biological compound functions in as many different types of biological reactions as S-adenosyl-L-methionine (known as SAM or AdoMet). It is probably second only to ATP in the variety of reactions for which it serves as a cofactor. SAM is found in all living organisms, and fulfills three important roles:
* In transmethylation, SAM is the principal biological methyl donor.
* In transsulfuration, the sulfur atom of the SAM molecule is converted via a series of enzymatic steps to cysteine, a precursor of taurine and glutathione, a major cellular anti-oxidant.
* In polyamine biosynthesis, SAM is the donor of aminopropyl groups.
The structure of SAM was first elucidated by Cantoni in 1951 [Cantoni51]. The key to SAM's activity lies in the presence of the high energy sulfonium ion, which activates each of the attached carbons toward nucleophilic attack. In most cases, SAM reacts by transfer of the S-methyl group to a long list of possible acceptors in transmethylation reactions.
SAM is synthesized in the cytosol of every cell from L-methionine and ATP; in E. coli, the reaction is catalyzed by methionine adenosyltransferase. In this unusual reaction, the adenosyl moiety of ATP is transferred to methionine, forming a sulfonium ion which is a high energy reagent that can easily transfer its methyl group to a large variety of acceptor substrates including nucleic acids, proteins, phospholipids, biologic amines, and a long list of small molecules [Lu00].
Arifuzzaman06: Arifuzzaman M, Maeda M, Itoh A, Nishikata K, Takita C, Saito R, Ara T, Nakahigashi K, Huang HC, Hirai A, Tsuzuki K, Nakamura S, Altaf-Ul-Amin M, Oshima T, Baba T, Yamamoto N, Kawamura T, Ioka-Nakamichi T, Kitagawa M, Tomita M, Kanaya S, Wada C, Mori H (2006). "Large-scale identification of protein-protein interaction of Escherichia coli K-12." Genome Res 16(5);686-91. PMID: 16606699
Chattopadhyay91: Chattopadhyay MK, Ghosh AK, Sengupta S (1991). "Control of methionine biosynthesis in Escherichia coli K12: a closer study with analogue-resistant mutants." J Gen Microbiol 137(3);685-91. PMID: 2033383
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Fu96: Fu Z, Hu Y, Markham GD, Takusagawa F (1996). "Flexible loop in the structure of S-adenosylmethionine synthetase crystallized in the tetragonal modification." J Biomol Struct Dyn 13(5);727-39. PMID: 8723769
Komoto04: Komoto J, Yamada T, Takata Y, Markham GD, Takusagawa F (2004). "Crystal structure of the S-adenosylmethionine synthetase ternary complex: a novel catalytic mechanism of S-adenosylmethionine synthesis from ATP and Met." Biochemistry 43(7);1821-31. PMID: 14967023
Lasserre06: Lasserre JP, Beyne E, Pyndiah S, Lapaillerie D, Claverol S, Bonneu M (2006). "A complexomic study of Escherichia coli using two-dimensional blue native/SDS polyacrylamide gel electrophoresis." Electrophoresis 27(16);3306-21. PMID: 16858726
LopezCampistrou05: Lopez-Campistrous A, Semchuk P, Burke L, Palmer-Stone T, Brokx SJ, Broderick G, Bottorff D, Bolch S, Weiner JH, Ellison MJ (2005). "Localization, annotation, and comparison of the Escherichia coli K-12 proteome under two states of growth." Mol Cell Proteomics 4(8);1205-9. PMID: 15911532
Markham84: Markham GD (1984). "Structure of the divalent metal ion activator binding site of S-adenosylmethionine synthetase studied by vanadyl(IV) electron paramagnetic resonance." Biochemistry 23(3);470-8. PMID: 6322838
Markham86: Markham GD (1986). "Characterization of the monovalent cation activator binding site of S-adenosylmethionine synthetase by 205Tl NMR of enzyme-bound Tl+." J Biol Chem 261(4);1507-9. PMID: 3511045
Markham87: Markham GD, Parkin DW, Mentch F, Schramm VL (1987). "A kinetic isotope effect study and transition state analysis of the S-adenosylmethionine synthetase reaction." J Biol Chem 262(12);5609-15. PMID: 3553181
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