S-Adenosyl-L-homocysteine explained

S-Adenosyl-L-homocysteine (SAH) is the biosynthetic precursor to homocysteine.^[1] SAH is formed by the demethylation of S-adenosyl-L-methionine.^{[2] [3]} Adenosylhomocysteinase converts SAH into homocysteine and adenosine.

Biological role

DNA methyltransferases are inhibited by SAH.^[4] Two S-adenosyl-L-homocysteine cofactor products can bind the active site of DNA methyltransferase 3B and prevent the DNA duplex from binding to the active site, which inhibits DNA methylation.^[5]

External links

• BioCYC E.Coli K-12 Compound: S-adenosyl-L-homocysteine

Notes and References

1. Finkelstein JD . Pathways and regulation of homocysteine metabolism in mammals . Seminars in Thrombosis and Hemostasis . 26 . 3 . 219–225 . 2000 . 11011839 . 10.1055/s-2000-8466 .
2. Ribbe MW, Hu Y, Hodgson KO, Hedman B . Biosynthesis of nitrogenase metalloclusters . Chemical Reviews . 114 . 8 . 4063–4080 . April 2014 . 24328215 . 3999185 . 10.1021/cr400463x .
3. James SJ, Melnyk S, Pogribna M, Pogribny IP, Caudill MA . Elevation in S-adenosylhomocysteine and DNA hypomethylation: potential epigenetic mechanism for homocysteine-related pathology . The Journal of Nutrition . 132 . 8 Suppl . 2361S–2366S . August 2002 . 12163693 . 10.1093/jn/132.8.2361S . free .
4. Kumar R, Srivastava R, Singh RK, Surolia A, Rao DN . Activation and inhibition of DNA methyltransferases by S-adenosyl-L-homocysteine analogues . Bioorganic & Medicinal Chemistry . 16 . 5 . 2276–2285 . March 2008 . 18083524 . 10.1016/j.bmc.2007.11.075 .
5. Lin CC, Chen YP, Yang WZ, Shen JC, Yuan HS . Structural insights into CpG-specific DNA methylation by human DNA methyltransferase 3B . Nucleic Acids Research . 48 . 7 . 3949–3961 . April 2020 . 32083663 . 7144912 . 10.1093/nar/gkaa111 .