S-Adenosylhomocysteine (SAH)
Product of SAMe after methyl group donation; must be rapidly converted to homocysteine to prevent methylation inhibition.
S-Adenosylhomocysteine (SAH) is the immediate product formed when S-adenosylmethionine (SAMe) donates its methyl group to an acceptor molecule. SAH is a potent competitive inhibitor of most methyltransferase enzymes, meaning it must be rapidly removed to allow continued methylation reactions.
The enzyme SAHH (S-adenosylhomocysteine hydrolase) cleaves SAH into homocysteine and adenosine. The SAMe:SAH ratio is considered a key indicator of cellular methylation capacity - a low ratio indicates methylation stress. Elevated SAH levels are associated with cardiovascular disease, neurological disorders, and impaired detoxification.
Anything that slows homocysteine clearance (B12, folate, B6 deficiency) can cause SAH accumulation.
Metabolic Connections
S-Adenosylhomocysteine (SAH) connects to 8 other pathways.
Enzymes
GNMT (Glycine N-Methyltransferase)
SAH is produced when GNMT uses SAMe
Enzyme that methylates glycine to sarcosine using SAMe; major regulator of SAMe levels; folate-inhibited.
SAHH (S-Adenosylhomocysteine Hydrolase)
SAHH enzyme converts SAH to homocysteine; this reaction is reversible and equilibrium-dependent
Enzyme that cleaves SAH into homocysteine and adenosine; reversible reaction dependent on product removal.
SAHH (S-Adenosylhomocysteine Hydrolase)
SAHH cleaves SAH to produce homocysteine and adenosine
Enzyme that cleaves SAH into homocysteine and adenosine; reversible reaction dependent on product removal.
Methylation
Homocysteine
SAH is cleaved by SAHH enzyme to produce homocysteine and adenosine
Sulfur-containing amino acid at the crossroads of methylation. Elevated levels indicate impaired methylation or B-vitamin deficiency.
Homocysteine
Homocysteine is produced when SAH is cleaved by SAHH
Sulfur-containing amino acid at the crossroads of methylation. Elevated levels indicate impaired methylation or B-vitamin deficiency.
SAMe
SAH is formed when SAMe donates its methyl group; SAH accumulation inhibits SAMe-dependent methylation
S-Adenosylmethionine - universal methyl donor essential for 200+ methylation reactions including neurotransmitter synthesis and DNA methylation.
SAMe
SAH is produced when SAMe donates its methyl group
S-Adenosylmethionine - universal methyl donor essential for 200+ methylation reactions including neurotransmitter synthesis and DNA methylation.
