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S-Adenosyl-L-homocysteine
Names
	IUPAC name S-(5′-Deoxyadenos-5′-yl)-L-homocysteine
	Systematic IUPAC name (2S)-2-Amino-4-({[(2S,3S,4R,5R)-5-(6-amino-9H-purin-9-yl)-3,4-dihydroxyoxolan-2-yl]methyl}sulfanyl)butanoic acid
	Other names AdoHcy, 2-S-adenosyl-L-homocysteine,; 5′-S-(3-Amino-3-carboxypropyl)-5′-thioadenosine S-adenosylhomocysteine, SAH
Identifiers
CAS Number	979-92-0 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:16680 ;
ChEMBL	ChEMBL418052 ;
ChemSpider	388301 ;
ECHA InfoCard	100.012.328
IUPHAR/BPS	5265;
KEGG	C00021 ;
MeSH	S-Adenosylhomocysteine
PubChem CID	439155;
UNII	8K31Q2S66S ;
CompTox Dashboard (EPA)	DTXSID30895860 ;
	InChI InChI=1S/C14H20N6O5S/c15-6(14(23)24)1-2-26-3-7-9(21)10(22)13(25-7)20-5-19-8-11(16)17-4-18-12(8)20/h4-7,9-10,13,21-22H,1-3,15H2,(H,23,24)(H2,16,17,18)/t6-,7+,9+,10+,13+/m0/s1 Key: ZJUKTBDSGOFHSH-WFMPWKQPSA-N ; InChI=1/C14H20N6O5S/c15-6(14(23)24)1-2-26-3-7-9(21)10(22)13(25-7)20-5-19-8-11(16)17-4-18-12(8)20/h4-7,9-10,13,21-22H,1-3,15H2,(H,23,24)(H2,16,17,18)/t6-,7+,9+,10+,13+/m0/s1 Key: ZJUKTBDSGOFHSH-WFMPWKQPBX;
	SMILES O=C(O)[C@@H](N)CCSC[C@H]3O[C@@H](n2cnc1c(ncnc12)N)[C@H](O)[C@@H]3O;
Properties
Chemical formula	C14H20N6O5S
Molar mass	384.41 g·mol−1
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

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]

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