Methylselenocysteine, also known as ''Se''-methylselenocysteine, is an
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 subs ...
progression and proliferation of premalignant mammary lesions and induces
apoptosis
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...
of cancer cell lines in culture."
Apoptosis
Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes incl ...
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
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...
rather than apoptosis, since selenite did not significantly induce several apoptotic phenomena, including the activation of
caspase-3."
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'' 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 onion ...
,
leek
The leek is a vegetable, a cultivar of ''Allium ampeloprasum'', the broadleaf wild leek ( syn. ''Allium porrum''). The edible part of the plant is a bundle of leaf sheaths that is sometimes erroneously called a stem or stalk. The genus ''Alli ...
,
garlic
Garlic (''Allium sativum'') is a species of bulbous flowering plant in the genus ''Allium''. Its close relatives include the onion, shallot, leek, chive, Allium fistulosum, Welsh onion and Allium chinense, Chinese onion. It is native to South A ...
,
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'' species (
broccoli,
radish,
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 cabbages ...
,
cabbage
Cabbage, comprising several cultivars of ''Brassica oleracea'', is a leafy green, red (purple), or white (pale green) biennial plant grown as an annual vegetable crop for its dense-leaved heads. It is descended from the wild cabbage ( ''B.&nb ...
), 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'' species,
) "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
Selenols are organic compounds that contain the functional group with the connectivity C– Se–H. Selenols are sometimes also called selenomercaptans and selenothiols. Selenols are one of the principal classes of organoselenium compounds. The be ...
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 sele ...
, 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 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