NANP Board Practice Exam

What can Methionine be converted to and used as in many biochemical pathways?

1. Cysteine

2. Glutamine

3. S-adenosylmethionine (SAM)

4. Taurine

The correct answer is: S-adenosylmethionine (SAM)

Methionine is an essential amino acid that plays a vital role in various biochemical pathways, primarily because it serves as a precursor for S-adenosylmethionine (SAM). SAM is a critical methyl donor in methylation reactions, which are integral to the regulation of gene expression, synthesis of neurotransmitters, and lipid metabolism, among other functions. The conversion of methionine to SAM involves the addition of adenosine triphosphate (ATP) and is facilitated by the enzyme methionine adenosyltransferase. This transformation is significant as it highlights the importance of methionine not just as an amino acid for protein synthesis, but also as a contributor to a variety of metabolic processes through SAM. While methionine can lead to the formation of other compounds, such as cysteine through transsulfuration pathways, and indirect connections to other amino acids like taurine, these pathways do not primarily showcase methionine's role as a methyl donor or the broader implications of its metabolism. Thus, the conversion of methionine to S-adenosylmethionine accurately represents one of the key biochemical roles that methionine plays in the body.