STABILITY 



Thiaminase 



C. A. Elvehjem and his co-workers ^^ appear to have been the first 

 to correlate the effect of feeding raw fish with aneurine deficiency. 

 They observed that the addition of 25 % of raw carp to a diet adequate 

 for the chick caused vitamin B^ deficiency, and that incubation of 

 aneurine with raw carp intestines for fifteen minutes resulted in a loss 

 of 50 to 100 % of the biological activity. C. A. Evans et al}^ showed 

 that the so-called Chastek paralysis of foxes, caused by feeding 10 % 

 or more of fresh whole fish in the diet, and of which the characteristic 

 symptoms are injuries to the liver and brain, could be prevented by 

 administration of 10 mg. of aneurine per day. The paralysis was 

 caused by feeding the skin, scales, skeleton and heads, but not the 

 muscle tissue, of carp. The viscera were particularly rich in the 

 responsible factor, which was shown to be a protein, probably enzymic 

 in character. The same conclusion was reached by P. S. Owen and 

 J. W. Ferrebee,^2 ^^\^q showed that the factor was destroyed by 

 cooking. The enzymic nature of the factor was confirmed by R. R. 

 Sealock and R. L. Goodland,^^ who showed that its destructive effect 

 on the vitamin was inhibited by certain inorganic substances, e.g. 

 copper, zinc and iron salts, potassium cyanide, sodium fluoride and 

 sodium sulphate, by certain organic compounds such as iodoacetic 

 acid and cysteine, known to inhibit enzymes and, most interesting of 

 all, by a number of thiazole and pyrimidine derivatives related to 

 aneurine. These included the 3-0-aminobenzyl, 3-jS-aminoethyl, 3-^- 

 phthalimidoethyl, 3-ethyl and 3-phenyl derivatives of 4-methyl- 

 thiazolium chloride and the 5-bromomethyl, 5-ethoxymethyl and 5- 

 methylene sulphonic acid derivatives of 4-amino-2-methylpyrimidine. 

 3-o-Aminobenzyl-4-methyl-thiazolium chloride actually competed with 

 aneurine for the enzyme of the Chastek principle. Other thiazole 

 compounds of this type were the benzyl, 0-, m- and _/)-nitrobenzyl and 

 the 0-, m-, and ^-aminobenzyl quaternary ammonium salts of 2- and 

 4-methyl- and 2 : 4-dimethyl-5-/8-hydroxyethyl thiazole.^* 3-w-Amino- 

 benzyl-4-methyl-thiazolium chloride, however, accelerated the destruc- 

 tion of aneurine by the enzyme ; so did w-nitraniline and w-amino- 

 benzoic acid.^^ This result was shown to be due to combination of 

 the amino group with the 5-methylene group of the pyrimidine moiety 

 formed by destruction of the aneurine, since N-(6-amino-2-methyl- 

 pyrimidyl-5 -methyl) -m-nitraniline was isolated from the product 

 formed by inactivation in the presence of w-nitraniline. 



The enzyme was shown ^^ to be present in raw herring as well as in 

 carp ; feeding either to cats resulted in the onset of vitamin B^ de- 

 ficiency with convulsions in twenty-three to forty days, followed by 

 death. The enzyme, to which the name thiaminase has been given, 



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