664 THE BIOCHEMISTRY OF B VITAMINS 



in erythrocyte count, hemoglobin, and hematocrit with a microcytic and 

 hypochromic anemia was observed in puppies receiving desoxypyri- 

 doxine. 69 The animals lost weight and died within two months. Monkeys 

 receiving desoxypyridoxine similarly developed microcytic anemia, 

 leucopenia and lymphopenia. 69 



Desoxypyridoxine inhibits the multiplication of T2r + Escherichia coli 

 bacteriophage without affecting growth of the bacteria. The inhibition 

 of virus production is prevented by sufficient pyridoxine, as well as by 

 formic, acetic, butyric, valeric and pyruvic acids, glucose-6-phosphate, 

 and less effectively by lactic, malic, fumaric and succinic acids. 76a 



Desoxypyridoxine is reported to inhibit the stimulatory action of 

 pyridoxine or pyridoxal for Saccharomyces cerevisiae. Pyridoxal appears 

 to be more effective in preventing the inhibitory action of low concentra- 

 tions of the analogue. 70 At low concentrations the analogue alone is 

 reported to stimulate the growth of a strain of Saccharomyces cerevisiae. 27 

 It is interesting to note that desoxypyridoxine has slight growth-promot- 

 ing activities for a number of microorganisms (Table 35). 



Since the effect of desoxypyridoxine is more pronounced in animals 

 with restricted vitamin B 6 intake, the mechanism of action of the in- 

 hibitor did not appear to be solely that of strict competition with the 

 vitamin. Desoxypyridoxine, even at concentration of 1 mg per cc, does 

 not affect tyrosine decarboxylase from Streptococcus faecalis R, 72 ' 77 

 aspartic-glutamic transaminase from heart muscle of the horse, 72 or the 

 tryptophanase system of Escherichia coli. 72 Once pyridoxal phosphate is 

 associated with these enzymes, desoxypyridoxine does not displace it. 

 Furthermore, desoxypyridoxine does not prevent the combination of 

 pyridoxal phosphate with apoenzymes of the decarboxylase or the tran- 

 saminase. 72 Desoxypyridoxine has no effect on the formation of pyridoxal 

 phosphate from pyridoxal and suboptimal amounts of adenosine tri- 

 phosphate in Streptococcus faecalis R. 72 However, when adenosine tri- 

 phosphate is present in excess and pyridoxal is limiting, desoxypyridoxine 

 exerts some effect when the mixture is assayed with the apoenzyme of 

 tyrosine decarboxylase from Streptococcus faecalis R. 72 This inhibition 

 is attributed to the formation of desoxypyridoxine phosphate. 



Desoxypyridoxine phosphate exerts no effect on 3,4-dihydroxyphenyl- 

 alanine decarboxylase 77a and only a slight effect on tyrosine decar- 

 boxylase. 72, 77 However, if it is allowed to compete with pyridoxal phos- 

 phate for the apoenzyme, either by addition prior to or simultaneous 

 with the natural coenzyme, complete inhibition of the tyrosine decar- 

 boxylase occurs at a ratio of inhibitor to coenzyme of 1000. 72 If the 

 apoenzyme is allowed to combine with the coenzyme first, desoxypyri- 

 doxine phosphate at the same relative concentration after a short incuba- 



