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.

Quick Facts Names, Identifiers ...

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 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:16680 Y
ChEMBL	ChEMBL418052 Y
ChemSpider	388301 Y
ECHA InfoCard	100.012.328
IUPHAR/BPS	5265
KEGG	C00021 Y
MeSH	S-Adenosylhomocysteine
PubChem CID	439155
UNII	8K31Q2S66S Y
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 Y Key: ZJUKTBDSGOFHSH-WFMPWKQPSA-N Y 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). Y verify (what is YN ?) Infobox references

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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]