Methylselenocysteine, also known as ''Se''-methylselenocysteine, is an

analog Analog or analogue may refer to: Computing and electronics * Analog signal, in which information is encoded in a continuous variable ** Analog device, an apparatus that operates on analog signals *** Analog electronics, circuits which use analog ...

of ''S''-methylcysteine in which the sulfur atom is replaced with a selenium atom. It is an inhibitor of DMBA-induced mammary tumors and a " chemopreventive agent that blocks

cell cycle The cell cycle, or cell-division cycle, is the series of events that take place in a cell that cause it to divide into two daughter cells. These events include the duplication of its DNA (DNA replication) and some of its organelles, and sub ...

progression and proliferation of premalignant mammary lesions and induces apoptosis of cancer cell lines in culture." Apoptosis has been proposed as the most plausible mechanism for the chemopreventive activities of selenocompounds. ''Se''-Methylselenocysteine was more efficient at inducing apoptosis than

selenite Selenite may refer to: Substances containing selenium *A selenium-containing anion or ionic compound with the SeO32− anion: **Selenite (ion), anion is a selenium oxoanion with the chemical formula SeO32− ***Selenous acid, the conjugate acid, w ...

, but was less toxic. The "selenite-induced cell death could be derived from necrosis rather than apoptosis, since selenite did not significantly induce several apoptotic phenomena, including the activation of

caspase-3 Caspase-3 is a caspase protein that interacts with caspase-8 and caspase-9. It is encoded by the ''CASP3'' gene. ''CASP3'' orthologs have been identified in numerous mammals for which complete genome data are available. Unique orthologs are also p ...

." In the Nutritional Prevention of Cancer Trial, selenized yeast resulted in "a reduction in the incidence of prostate cancer and in total cancer incidence"; subsequent anticancer studies using selenomethionine did not show any benefit against cancer; but, selenized yeast contains both selenomethionine and methylselenocysteine. Methylselenocysteine is found in selenized yeast, and many vegetables: "As much as 80% of the total selenium" found in ''

Allium ''Allium'' is a genus of monocotyledonous flowering plants that includes hundreds of species, including the cultivated onion, garlic, scallion, shallot, leek, and chives. The generic name ''Allium'' is the Latin word for garlic,Gledhill, D ...

'' species (

onion An onion (''Allium cepa'' L., from Latin ''cepa'' meaning "onion"), also known as the bulb onion or common onion, is a vegetable that is the most widely cultivated species of the genus ''Allium''. The shallot is a botanical variety of the onio ...

, leek, garlic,

ramps An inclined plane, also known as a ramp, is a flat supporting surface tilted at an angle from the vertical direction, with one end higher than the other, used as an aid for raising or lowering a load. The inclined plane is one of the six clas ...

) ''

Brassica ''Brassica'' () is a genus of plants in the cabbage and mustard family ( Brassicaceae). The members of the genus are informally known as cruciferous vegetables, cabbages, or mustard plants. Crops from this genus are sometimes called ''cole c ...

'' species (

broccoli Broccoli (''Brassica oleracea'' var. ''italica'') is an edible green plant in the cabbage family (family Brassicaceae, genus ''Brassica'') whose large flowering head, stalk and small associated leaves are eaten as a vegetable. Broccoli is cla ...

radish The radish (''Raphanus raphanistrum'' subsp. ''sativus'') is an edible root vegetable of the family Brassicaceae that was domesticated in Asia prior to Roman times. Radishes are grown and consumed throughout the world, being mostly eaten raw ...

Brussels sprouts The Brussels sprout is a member of the Gemmifera cultivar group of cabbages (''Brassica oleracea''), grown for its edible buds. The leaf vegetables are typically 1.5–4.0 cm (0.6–1.6 in) in diameter and resemble miniature cabbag ...

, cabbage), and

milk vetch ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to ...

(''

Astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...

'' species, Fabaceae) "is present as ''Se''-methylselenocysteine." The bioavailability of selenium from ''Se''-methylselenocysteine, "is likely to be similar to that from other organic selenium compounds." Specifically, "It is converted via the action of β-lyase, to methylselenol and then to

hydrogen selenide Hydrogen selenide is an inorganic compound with the formula H2Se. This hydrogen chalcogenide is the simplest and most commonly encountered hydride of selenium. H2Se is a colorless, flammable gas under standard conditions. It is the most toxic sel ...

, which is also the key metabolite derived from" all other common forms of selenium. But EFSA concluded that "given the absence of human studies on ''Se''-methylselenocysteine, the relatively sparse database on the

bioavailability In pharmacology, bioavailability is a subcategory of absorption and is the fraction (%) of an administered drug that reaches the systemic circulation. By definition, when a medication is administered intravenously, its bioavailability is 100%. Ho ...

of selenium from this source and the limited data on the safety of this source compared with other selenium compounds, the Upper Limit for selenium defined by the

Scientific Committee on Food The Scientific Committee on Food (SCF), established in 1974, was the main committee providing the European Commission with scientific advice on food safety. "Scientific Committee on Food - FOOD STANDARDS AGENCY" (overview), Gov.uk, F ...

cannot be used for judging its safety."

References

{{Reflist Amino acid derivatives Organoselenium compounds Selenium(−II) compounds Selenoethers