Thiaminases (Vitamin B1: Deficiency)
Thiaminases are enzmyes found in certain fish, shellfish, and plants. When ingested these enzymes split thiamin (Vitamin B1), an important compound in energy metabolism, and render it inactive.
In general then, excessive amounts of Thiaminase are connected with symptoms of sickness that include poor growth, loss of appetite, abdominal swelling and hemorrhage, loss of equilibrium, convulsions, muscle atrophy and a weak immune system.
The B vitamin thiamine is essential for the metabolism of carbohydrates into simple glucose sugar.
Vitamin B1 is as important to animals as it is to ourselves. Without adequate supplies, humans develop a sickness called beriberi — and symptoms include lethargy, weight loss, problems with nerve control and sense organs, heart failure, and eventually death.
Thiaminases are enzymes that cleave the thiamin molecule and render it biologically inactive. Generally there are two types of thiaminases:
Type I - the most common form, this type is found in fish, shellfish, ferns and some bacteria. It acts by displacing the pyrimidine methylene group with a nitrogenous base or SH-compound to eliminate the thiazole ring.
Type II - found in certain bacteria, this type acts through the hydrolytic cleavage of the methylene-thiazole-N bond to yield pyrimidine and thiamin moieties.
While freezing does not destroy Thiaminase, heating it will. This is why cooked fish is not dangerous with regard to Thiaminase for human or animal nutrition. From the perspective of a fishkeeper, the big drawback to cooking food is that heating destroys a lot of the useful nutrients as well. While omnivorous humans compensate for that by eating a varied diet containing both raw and cooked plant and animal foods, piscivorous fish have no such option. They cannot be fed cooked fish and expected to stay healthy.
At least some types of live feeder fish will contain more Vitamin B1 than frozen foods, but the downside here is that the convenience of live foods is accompanied by a major risk of introducing pathogenic microorganisms such as Mycobacteria and endoparasites. Feeder fish are also expensive compared with frozen foods, and as will be described shortly, many of the types of feeder fish widely sold contain a great deal of Thiaminase anyway, dramatically reducing their usefulness.
Thiaminase content review
The data on Thiaminase content comes from various sources, mostly from the National research council (1982), Deutsch & Hasler (1943), Greig & Gnaedinger (1971) and Hilker & Peter (1966); see also the literature list at the end of the article. The lists are far from complete, but most of the usually marketed and so far examined species are enlisted. Although primarily based on coldwater food fish and invertebrates, Thiaminase content information exists for several tropical species widely marketed, and these been included accordingly.
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