sarcosine

Sarcosine, or N-methylglycine, is a naturally occurring amino acid–derivative. It is the N-methylated form of glycine and exists as a zwitterion under physiological conditions. Its chemical formula is C3H7NO2, and it is sometimes described as a nonessential amino acid–like metabolite rather than a standard proteinogenic amino acid.

In humans and other organisms, sarcosine is produced from glycine by the action of the enzyme glycine N-methyltransferase (GNMT), which uses S-adenosylmethionine as the methyl donor. The compound is found in tissues and fluids, including liver tissue and urine, where it arises from normal methylation and amino acid metabolism.

Metabolically, sarcosine functions as an intermediate in one-carbon metabolism. It can be further metabolized to glycine, primarily through mitochondrial enzymes such as sarcosine dehydrogenase, which links sarcosine turnover to cellular redox and energy balance. Through these pathways, sarcosine participates in the broader network of methyl group transfers and amino acid interconversions.

Sarcosine has attracted attention in biomedical research, particularly as a potential biomarker for cancer. In the early 2000s, studies proposed elevated sarcosine levels as indicative of aggressive prostate cancer. Subsequent investigations yielded mixed results, and sarcosine is not currently adopted as a validated clinical biomarker. Outside of research contexts, it remains a metabolite of interest for understanding one-carbon metabolism and amino acid interconversion.