Thiamine

Thiamine
Systematic name	Thiamine
Molecular formula	C12H17N4OS
Molecular mass	266.4 g/mol
Density	x.xxx g/cm3
Melting point	248-250 °C (hydrochloride salt)
Boiling point	xx.x °C
CAS number	[59-43-8] [1]
SMILES	xxxx
Disclaimer and references

For the similarly-spelled nucleic acid, see Thymine

Thiamine or thiamin, also known as vitamin B₁, is one of the B vitamins, a group of chemically distinct, water-soluble vitamins that also includes riboflaven, niacin, pantothenic acid, pyridoxine, biotin, folic acid, and others. A colorless compound with chemical formula C₁₂H₁₇N₄OS, thiamine's chemical structure contains a pyrimidine ring and a thiazole ring. It is insoluble in alcohol, and decomposes if heated.

As a vitamin, thiamine is an organic (carbon-containing) nutrient obtained through the diet and essential in small amounts for normal metabolic reactions in humans. Thiamine plays an important role in helping the body convert carbohydrates and fat into energy. It is essential for normal growth and development and helps to maintain proper functioning of the heart and the nervous and digestive systems. It serves as a co-enzyme in the pathway to synthesize NADPH and the pentose sugars deoxyribose and ribose, the later two of which are the sugars for DNA and RNA, respectively.

Since it is water-soluble, thiamine cannot be stored in the body; however, once absorbed, the vitamin is concentrated in muscle tissue. Among good sources are various vegetables, including legumes and green peas, as well as liver, nuts, and yeast. Beriberi is one well-known disease caused by a deficiency of thiamine.

Overview

Thiamine was first discovered in 1910 by Umetaro Suzuki in Japan when researching how rice bran cured patients of beriberi. He named it aberic acid. Suzuki did not determine its chemical composition, nor that it was an amine.

Thiamine was first crystallized by Jansen and Donath in 1926. (They named it aneurin, for antineuritic vitamin). Thiamine's chemical composition and synthesis was finally reported by Robert R. Williams in 1935. He also coined the name for it, thiamin.

There are four known natural thiamine phosphate derivatives: thiamine monophosphate (ThMP), thiamine diphosphate (ThDP), thiamine triphosphate (ThTP) and the recently dicovered adenine thiamine triphopshate (AThTP).

In mammals, thiamine diphosphate (ThDP) or thiamine pyrophosphate (TPP) is a coenzyme for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase, branched-chain alpha-keto acid dehydrogenase, 2-hydroxyphytanoyl-CoA lyase, and transketolase. The first two of these enzymes function in the metabolism of carbohydrates, while transketolase functions in the pentose phosphate pathway to synthesize NADPH and the pentose sugars deoxyribose and ribose. Deoxyribose is the sugar component of DNA, just as ribose serves that role in RNA (ribonucleic acid). ThDP is also the cofactor of pyruvate decarboxylase in yeast and of several bacterial enzymes.

In general, TPP functions as a cofactor for enzymes that catalyze the dehydrogenation (decarboxylation and subsequent conjugation to Coenzyme A) of alpha-keto acids. TPP is synthesized by the enzyme thiamine pyrophosphokinase, which requires free thiamine, magnesium, and adenosine triphosphate (ATP).

Thiamine triphosphate (ThTP) was long considered a specific neuroactive form of thiamine. However, recently it was shown that ThTP exists in bacteria, fungi, plants and animals, suggesting a much more general cellular role. In particular, in Escherichia coli it seems to play a role in response to amino acid starvation.

Adenosine thiamine triphosphate (AThTP), or thiaminylated adenosine triphosphate, has recently been discovered in E. coli where it accumulates as a result of carbon starvation. In E. coli, AThTP may account for up to 20% of total thiamine. It also exists in lesser amounts in yeast, roots of higher plants, and animal tissues.

Nutrition, deficiency, and overdose

Thiamine is found naturally in the following foods, each of which contains at least 0.1 mg of the vitamin per 28-100g (1-3.5oz): Green peas, spinach, liver, beef, pork, Navy beans, Nuts, Pinto beans, soybeans, shole-grain and enriched eereals, breads, yeast, and legumes.

Systemic thiamine deficiency can lead to myriad problems, including neurodegeneration, wasting, and death. A lack of thiamine can be caused by malnutrition, alcoholism, a diet high in thiaminase-rich foods (raw freshwater fish, raw shellfish, ferns) and/or foods high in anti-thiamine factors (tea, coffee, betel nuts) (Higdon 2002).

Well-known syndromes caused by thiamine deficiency include Wernicke-Korsakoff syndrome and beriberi, diseases also common with chronic alcoholism.

A positive diagnosis test for thiamine deficiency can be ascertained by measuring the activity of transketolase in erythrocytes . Thiamine can also be measured directly in whole blood following the conversion of thiamine to a fluorescent thiochrome derivative. The aleurone layer of unpolished rice is a rich source.

The only known cases of thiamine overdose occurred with thiamine injections. Thiamine injection may result in anaphylactic reactions.

Genetic diseases

{{#invoke:Message box|ambox}} Genetic diseases of thiamine transport are rare but serious. Thiamine Responsive Megaloblastic Anemia with diabetes mellitus and sensorineural deafness (TRMA) is an autosomal recessive disorder caused by mutations in the gene SLC19A2, a high affinity thiamine transporter. TRMA patients do not show signs of systemic thiamine deficiency, suggesting redundancy in the thiamine transport system. This has led to the discovery of a second high affinity thiamine transporter, SLC19A3.

Mendelian Inheritance in Man (OMIM) 249270

Research

The RDA in most countries is set at about 1.4 mg. However, tests on volunteers at daily doses of about 50 mg have shown an increase in mental acuity.

Derrick Lonsdale lead a successful study on the treatment of autism spectrum children with thiamine. This work is controversial linking diet with autism.

References

ISBN links support NWE through referral fees

[2]

2002. .

External links

Template:ChemicalSources

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

• Thiamine  ^history

The history of this article since it was imported to New World Encyclopedia:

• History of "Thiamine"

Note: Some restrictions may apply to use of individual images which are separately licensed.