What is thiaminase?

Thiamin requirement can be greatly increased with the consumption of anti-thiamin substances in foods. Substances with an anti-thiamin activity are fairly common in nature and include structurally similar antagonists as well as structure-altering antagonist and thiamin degrading enzymes (thiaminases).

Thiaminase can cleave the vitamin B1 and render it inactive. People have acquired vitamin B1 or thiamin deficiency by eating raw clams and raw fish as a major part of their diet. This antagonist is easily destroyed by cooking.

The presence of thiaminase was discovered in clams by Fujita and Matsukawa in 1942 and in fresh-water fish by Green (1941, 1942).

Among fresh-water fish, carp and crusian carp exceed other species in the potency of this particular enzyme, which is most abundant in kidneys, intestines and gills.

Heat processing destroys thiaminase, which destroys thiamin in fish, shellfish, brussels sprouts, and red cabbage. In countries where large amounts of fish are eaten raw, human thiamin deficiency may occur.
What is thiaminase?

Thiamin in food

Thiamin also known as vitamin B1 and aneurin was the first B vitamin identified.

Thiamin (vitamin B1), the structural formula of which consists of substituted pyrimidine and thiazole rings linked by a methylene bridge.

All plant and animal tissues contain thiamin and it is therefore present in all natural unprocessed foods.

Rich sources of thiamin include yeasts and yeast extract, wheat bran, oatmeal, whole grain cereals, pulses, nuts, lean pork, heart, kidney and liver.

Lack of thiamin causes the deficiency disease called beriberi, which has been known since antiquity. Beriberi is rare in United States because grain products that are not whole grain are routinely enriched.

A deficiency of thiamin in humans can also result in Wenicke-Korsakoff’s encephalopathy, which is characterized by mental confusion and deterioration of nerve function leading at worst to coma.
Thiamin in food

Thiamin in human body

The thiamin molecule comprises substituted pyrimidine and thiazole moieties linked by a methylene bridge. 

Vitamin B1 was given the name thiamin because it contains a thiol (sulfur) group and an amine (nitrogen) group.

Thiamin functions as a coenzyme in the metabolism of carbohydrates and branched chain amino acids. Although thiamin, per se, is not an energy-yielding nutrient, its coenzyme form TPP is needed for ATP production.

TPP or thiamin triphosphate functions as a coenzyme, catalyzing reactions that enable the body to use glucose, amino acids and fatty acids for energy.

Absorption of thiamin occurs mainly in the jejunum, at lower concentration as an active, carrier mediated system involving phosphorylation and at higher concentration by passive diffusion.

The classic pathological condition rusting from a gross deficiency of thiamin in humans is beriberi, which is prevalent in Far Eastern populations where unfortified polished rice is staple diet.
Thiamin in human body

Absorption and Transport of Thiamin

Absorption and Transport of Thiamin
The bioavailability of thiamin occurring naturally in foods is believed to be high. Foods containing the highest concentration of thiamin are listed below:
Yeasts
Pork
Sunflower seeds
Legumes

Occasionally, however, anti-thiamin factor may be present in the diet. For example, thiaminases present in the raw fish catalyze the cleavage of thiamin, thereby destroying its activity.

These thiaminases are thermolabile, however and cooking of fish rendered the enzymes inactive. Other anti-thiamin factors that are thermostable may be found in tea and certain fruits and vegetables such as blueberries, black currents, Brussels sprouts and red cabbage.

Absorption of thiamin can be both active and passive, depending upon the amount of the vitamin presented for absorption.

At low physiologic concentrations, thiamin absorption is an active process. This Na+ dependent, carrier mediated absorption occurs primarily in the jejunum but can occur in other portions of the small intestine as well.

When intakes of thiamin are high, the absorption route is predominantly passive. The rate of thiamin absorption is always quite high except in the case of ethanol ingestion and/or folate deficiency.

Ethanol ingestion interferes with active transport of thiamin, and folate deficiency prevents the normal duplication of enterocytes, thereby decreasing absorption, both active and passive.

Within the mucosal cells, thiamin is converted into a phosphate ester, in which form it move into the plasma. To be active as a coenzyme, thiamin must be converted to its pyrophosphate (diphosphate) form.

Conversion to the active coenzyme form requires adenosine triphosphate (ATP) and thiamin pyrophosphokinase, an enzyme found in the liver and brain (and perhaps in other tissue as well).

Another form of thiamin (thiamin triphosphate, or ATP) is synthesized in the brain by action of a thiamin diphosphate (ADP) – ATP phosphoryl-transferase.
Absorption and Transport of Thiamin

Thiamin

Thiamin
Thiamin (vitamin B1) consists of a pyrimidines ruing and a thiazole moiety.

This vitamin is found widely distributed in foods, but the only foods considered good sources of thiamin are pork and whole grain or enriched grain products.

Persons who diets are made up primarily of refined, unenriched grain products are at extreme risk for becoming thiamin deficient and perhaps developing beriberi.

Beriberi is rare in United States because grain products that are not whole grain are routinely enriched.

Beriberi puzzled medical experts for years as it ravaged people of all ages in Asia. Doctors thought it was caused by something in food.

Not until the early 1900s did scientists discover that rice bran, the outer covering that was removed to create the polished white rice preferred by Asians, actually contained something that prevented the disease.

Thiamine was the first vitamin identified. In the 1920s, extracts of rice polishing were used to treat the disease.
Thiamin

B Vitamins – Thiamin and Riboflavin

B Vitamins – Thiamin and Riboflavin
Thiamin
The B vitamins are water soluble. Thiamin – vitamin B1 is involved in all bodily oxidations that lead to the formation of carbon dioxide. It is necessary for nerve function, appetite, and normal digestion. It is also required for growth, fertility, and lactation. The symptoms of vitamin deficiency are retardation of growth, palpitation and enlargement of the heart, hypertension, and beriberi. The various effects of a disturbance of the nerve centers such as forgetfulness or difficulty in thinking are other manifestations of vitamin B1 deficiency. The vitamin is often lacking in the diet because much of the naturally occurring amounts of it in food are destroyed during the processing of the food. The adult requirement of vitamin B1 is related to the food (calorie) intake. Fresh pork is an excellent source of vitamin B1 and the heart, liver, and kidneys of pork, beef and lamb are fair sources.

Riboflavin
Riboflavin – vitamin B2 is water soluble. This vitamin makes up a part of enzyme systems involved in the oxidation and reduction of different materials in the body. Deficiency of riboflavin generally results in growth retardation and may result in vision impairment, sealing of the skin, and lesions on mucous tissue. Neuritis is another deficiency effect. The minimum intake of riboflavin for an adult is about 2.0mg per day. The liver and kidney of pork, beef, and lamb are excellent sources of riboflavin, and the heart of these animals is a good source. Fair amounts of riboflavin are found in the muscular tissues of pork, beef, and lamb, while more is found in veal.
B Vitamins – Thiamin and Riboflavin