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?