S-adenosyl-L-homocysteine is an organic sulfide that is the S-adenosyl derivative of L-homocysteine. It has a role as a cofactor, an EC 2.1.1.79 (cyclopropane-fatty-acyl-phospholipid synthase) inhibitor, an EC 2.1.1.72 [site-specific DNA-methyltransferase (adenine-specific)] inhibitor, a fundamental metabolite and an epitope. It is a member of adenosines, an organic sulfide, a homocysteine derivative and a member of homocysteines. It is a conjugate acid of a S-adenosyl-L-homocysteinate. It is a tautomer of a S-adenosyl-L-homocysteine zwitterion.