S-adenosylmethionine-dependent methylation pathway (SAM-dependent methylation)

S-adenosylmethionine (SAM)-dependent methylation pathways constitute a vital network of biochemical reactions where SAM acts as the primary methyl group donor for various biological acceptors, including nucleic acids, proteins, and small molecules. These pathways are essential for maintaining cellular homeostasis, regulating gene expression through epigenetic modifications, and facilitating the synthesis of neurotransmitters and membrane lipids (Loenen, 2006). Dysregulation of SAM-dependent processes is a hallmark of several diseases; for instance, DNA hypermethylation can silence tumor suppressor genes in cancer, while impaired methylation is linked to neurodegenerative conditions like Alzheimer's disease (Baylin & Jones, 2011; Bottiglieri, 2005). Therapeutic strategies often involve the use of small molecule inhibitors to target specific methyltransferases, such as DNA methyltransferases (DNMTs) or histone methyltransferases (HMTs), to restore normal methylation patterns (Jones et al., 2016). However, because SAM is a ubiquitous cofactor, drugs targeting these pathways must be carefully designed to avoid widespread systemic toxicity and unintended epigenetic consequences.

Other names

SAM cycleMethionine cycleOne-carbon metabolismMethylation cycleS-adenosylmethionine-dependent methyltransferase activity

Inhibition of specific methyltransferase enzymes (e.g., DNMT, HMT, COMT), depletion of the methyl donor S-adenosylmethionine, or modulation of the methionine cycle to alter global or site-specific methylation patterns.