S-methyltransferase

S-methyltransferase is a type of enzyme that belongs to the larger family of transferases, specifically those transferring one-carbon group as methyl groups (methyltransferases). S-methyltransferases play a crucial role in the biological process known as methylation, where a methyl group (CH3) is added to a substrate molecule. This process is vital for a wide range of biological functions, including the modification of DNA, RNA, proteins, and lipids, which in turn affects gene expression, protein function, and cell signaling.

Function

S-methyltransferases catalyze the transfer of a methyl group from a donor, typically S-adenosylmethionine (SAM), to the sulfur atom of a thiol group in substrates, forming S-methylated products. This enzymatic activity is essential in the metabolism of sulfur-containing amino acids, such as methionine and cysteine, and plays a significant role in the biosynthesis of important biomolecules like glutathione, a major antioxidant in cells.

Classification

S-methyltransferases are classified under EC 2.1.1.- in the Enzyme Commission number system. They are further categorized based on their substrate specificity and the biological processes they are involved in. For example, thiol S-methyltransferase (TMT) is an enzyme that specifically methylates thiols in various substrates, playing a role in detoxification processes.

Biological Importance

The methylation process mediated by S-methyltransferases is crucial for cellular homeostasis and human health. Aberrant methylation patterns, often caused by the malfunction of these enzymes, have been linked to a range of diseases, including cancer, neurodegenerative diseases, and cardiovascular diseases. Understanding the function and regulation of S-methyltransferases is therefore important for the development of therapeutic strategies targeting these enzymes.

Examples

Some well-studied S-methyltransferases include:

• Thiol S-methyltransferase (TMT) - involved in detoxification of xenobiotics and endogenous compounds by methylation.
• Nicotianamine synthase (NAS) - involved in the biosynthesis of nicotianamine, a precursor of phytochelatins that play a role in metal detoxification in plants.

Pharmacological Relevance

Given their role in critical biological processes, S-methyltransferases are considered potential targets for drug development. Inhibitors or modulators of these enzymes could be used to treat diseases associated with dysregulated methylation, such as cancer. Research in this area is ongoing, with the aim of developing selective and potent inhibitors of specific S-methyltransferases.

See Also

• Methyltransferase
• Methylation
• S-adenosylmethionine
• Enzyme inhibitor