S-Adenosylhomocysteine

S-Adenosylhomocysteine (SAH) is a biochemical compound that plays a significant role in various metabolic processes within the human body. It is a common substrate in transmethylation reactions and is a crucial intermediate in the synthesis of homocysteine.

Structure and Properties

SAH is a homocysteine molecule linked to an adenosyl group via a sulfur atom. It is a chiral compound, meaning it has a non-superimposable mirror image. The molecule is polar due to the presence of several polar groups, including an amino group, a carboxyl group, and a hydroxyl group.

Biological Role

In the human body, SAH is produced from S-adenosylmethionine (SAM) during the process of methylation. This reaction is catalyzed by various methyltransferase enzymes. After its formation, SAH can be hydrolyzed to form adenosine and homocysteine, a reaction catalyzed by the enzyme S-adenosylhomocysteine hydrolase.

SAH is a potent inhibitor of most SAM-dependent methyltransferases due to its high affinity for these enzymes. This makes the regulation of SAH levels in the body crucial for maintaining normal cellular function.

Clinical Significance

Abnormal levels of SAH in the body have been associated with various health conditions. Elevated levels of SAH have been observed in patients with cardiovascular disease, liver disease, and neurodegenerative disorders. It is also a potential biomarker for vitamin B12 deficiency.

See Also

• S-adenosylmethionine
• Homocysteine
• Methylation
• Methyltransferase