Mimosine or leucenol is a toxic non-protein amino acid chemically similar to

tyrosine -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a non-essential amino acid with a polar side group. The word "tyrosine" is from the Gr ...

. It occurs in some ''

Mimosa ''Mimosa'' is a genus of about 590 species of herbs and shrubs, in the mimosoid clade of the legume family Fabaceae. The generic name is derived from the Greek word (''mimos''), an "actor" or "mime", and the feminine suffix -''osa'', "resemb ...

'' spp. (including '' M. pudica'') and all members of the closely related

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

'' Leucaena''. This compound, also known as leucenol, was first isolated from the seeds of '' Leucaena glauca'' Benth., and was later investigated by Adams and coworkers.

Properties

Mimosine melts with decomposition. The

hydrochloride In chemistry, a hydrochloride is an acid salt resulting, or regarded as resulting, from the reaction of hydrochloric acid with an organic base (e.g. an amine). An alternative name is chlorhydrate, which comes from French. An archaic alternative ...

salt melts at 174.5–175.0 °C with decomposition; the hydrobromide decomposes at 179.5 °C, and the hydroiodide decomposes at 183–183.5 °C. Mimosine only forms monobasic acids, but the methyl ester forms a dihydrochloride, C₇H₉O₂N₂(COOMe)•2 HCl•½ H₂O, mp. 175–6 °C.

Biological effects

Mimosine arrests dividing cells in the late G1 phase by inhibiting DNA replication initiation. In

ruminant Ruminants ( suborder Ruminantia) are hoofed herbivorous grazing or browsing mammals that are able to acquire nutrients from plant-based food by fermenting it in a specialized stomach prior to digestion, principally through microbial actions. Th ...

s, mimosine is degraded to 3,4- and 2,3-dihydroxypyridone (3,4- and 2,3-DHP). Although

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

osis has occurred in Australia,

Papua New Guinea Papua New Guinea (abbreviated PNG; , ; tpi, Papua Niugini; ho, Papua Niu Gini), officially the Independent State of Papua New Guinea ( tpi, Independen Stet bilong Papua Niugini; ho, Independen Stet bilong Papua Niu Gini), is a country i ...

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

and

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, a ...

, it has not been recorded in any other

tropical The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S. The tropics are also referred to ...

and subtropical regions.

Goat The goat or domestic goat (''Capra hircus'') is a domesticated species of goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a member of ...

s in

Burma Myanmar, ; UK pronunciations: US pronunciations incl. . Note: Wikipedia's IPA conventions require indicating /r/ even in British English although only some British English speakers pronounce r at the end of syllables. As John C. Wells, Joh ...

lost hair when fed a diet containing 50% of '' Leucaena''. Goats and

cattle Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus '' Bos''. Adult females are referred to as cows and adult ...

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only ...

are able to degrade the 3,4-DHP ruminally. Tolerance might be related to the presence or absence of

microbe A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s tolerant to mimosine and 3,4-DHP. It is known that at least Australian goats do not share the abilities of their Hawaiian counterparts. Bickel and Wibaut found in feeding experiments with rats and mice that leucenol is probably the toxic constituent of '' Leucaena glauca'' seeds, but they did not observe with these animals the loss of hair that seems to occur when these seeds are fed to cattle. Aung from Myanmar isolated the new subspecies of ''

Klebsiella pneumoniae ''Klebsiella pneumoniae'' is a Gram-negative, non-motile, encapsulated, lactose-fermenting, facultative anaerobic, rod-shaped bacterium. It appears as a mucoid lactose fermenter on MacConkey agar. Although found in the normal flora of the mouth ...

'' that can degrade mimosine. Besides, Moe Thida Htun, from Myanmar also found another new sub-species of Baccilus aureus that can degrade mimosine. Some rhizobia are known to produce rhizomimosinase, which consumes pyridoxal 5′-phosphate to degrade mimosine into 3,4 dihydroxypyridine,

pyruvate Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic aci ...

, and

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternar ...

. A similar enzyme, mimosinase, is produced by ''

Leucaena leucocephala ''Leucaena leucocephala'' is a small fast-growing mimosoid tree native to southern Mexico and northern Central America (Belize and Guatemala) and is now naturalized throughout the tropics including parts of Asia. Common names include jumbay, ...

''.

References

{{Reflist Amino acids 4-Pyridones Plant toxins Toxic amino acids

Properties

Biological effects

See also

References