L-Selenomethionine

L-Selenomethionine (CAS No.: 3211-76-5) is a naturally occurring selenium-containing amino acid and the predominant organic form of selenium found in dietary sources such as cereal grains, soybeans, legumes, and selenium-enriched yeast, widely utilized in biomedical research as a nutritional, biochemical, and pharmacological tool. As an L-isomer incorporated nonspecifically into proteins in place of methionine, it serves both as a selenium reservoir and as a functional modulator of redox biology, contributing to cellular antioxidant defense through depletion of reactive oxygen species and enhancement of glutathione synthesis and recycling. L-Selenomethionine is known to upregulate key selenoenzymes, including glutathione peroxidase, thioredoxin reductase, and glutathione reductase, thereby influencing redox-sensitive signaling pathways and cellular homeostasis. In cancer biology, it has been characterized as a chemopreventive agent capable of modulating cell cycle progression and inducing apoptosis in certain tumor cell lines, with reported activity in the low micromolar range in vitro while sparing non-malignant cells under comparable conditions. Owing to its higher bioavailability relative to inorganic selenium forms, it is frequently employed in cell-based assays, animal nutrition studies, and oxidative stress models, as well as in structural biology applications where its incorporation into recombinant proteins enhances phase determination in X-ray crystallography. Experimental concentrations and dosing regimens vary depending on the specific cellular context and research objectives, particularly in studies investigating redox regulation, cancer therapeutics, and selenium metabolism.