Seleno-L-Methionine (SeMet), an organic form of selenium is found in Cupriavidus metallidurans.

Seleno-L-methionine has been used:

• in toxicity studies in Japanese Medaka embryos
• to study its effects on selenium status indicators in pregnant long-tailed macaques (Macaca Fascicularis)
• to label proteins for single wavelength anomalous dispersion (SAD) phasing

Seleno-L-methionine has been used:

• as a nonchemical stressor to treat Japanese Medaka fish embryos
• to label proteins for Single wavelength Anomalous Dispersion (SAD) phasing
• to study the distribution and inhibition effects of seleno-L-methionine on 4T1 mouse mammary carcinoma

Seleno-L-Methionine (SeMet) is capable of repressing atopic dermatitis (AD)-like skin lesions. It can also prevent the expression of total immunoglobulin E (IgE) and interleukin 4 (IL-4). It can cause ecotoxicity as it is absorbed by fish through diet.

Seleno-L-methionine displays antioxidant activity and has been shown to increase the activity of glutathione peroxidase in endothelial cells. Glutathione peroxidase protects cells from oxidative damage, such as DNA strand breaks, mutations and interference with protein tyrosine-based signaling and other protein functions due to formation of 3-nitrotyrosine, caused by excessive peroxynitrite. Seleno-L-methionine administration to cancer cell lines (MCF-7/S breast carcinoma, DU-145 prostate cancer cells and UACC-375 melanoma) results in apoptotic cell death and aberrant mitosis. These human tumor cell lines exhibited dose-dependent growth inhibition by selenomethionine in the micromolar range (45 to 130μM), while growth inhibition of normal fibroblasts required 1mM selenomethionine.