PYRIDOXINE 



with those obtained with Neurospora sitophila (see below). The 

 successful use of 5. carlsbergensis for microbiological assays has been 

 reported by R. H. Hopkins and R. J. Pennington. ^^ 



" Pseudo-pyridoxine ", Pyridoxal and Pyridoxamine 



Streptococcus faecalis R, previously known as S. lactis R, requires 

 pyridoxine for growth, but when attempts were made to utilise it for 

 the assay of pyridoxine it was found ^'^ that the growth response was 

 much greater, several times greater in fact, than could be accounted 

 for by the pyridoxine content, as estimated chemically or biologically. 

 It appeared that pyridoxine was converted, prior to its utilisation by 

 the organism, into a more active metabolite, provisionally termed 

 " pseudo-pyridoxine " ; this also appeared to be present in some 

 natural products. Although it was so much more active than pyri- 

 doxine on 5. faecalis R " pseudo-pyridoxine ", formed either by 

 treating synthetic pyridoxine with hydrogen peroxide or by auto- 

 claving in presence of cystine, did not stimulate the growth of rats or 

 yeast to a greater extent than did pyridoxine. ^^ 



The nature of " pseudo-pyridoxine " was elucidated by E. E. 

 Snell,^^ who showed that substances with a greater growth-promoting 

 action on both S. faecalis R and Lactobacillus helveticus could be formed 

 from pyridoxine by amination or by partial oxidation. Treatment 

 with ammonia yielded a closely related amine, which he called pyri- 

 doxamine, whilst oxidation yielded an aldehyde, pyridoxal. Both 

 compounds were more active towards S. faecalis and L. helveticus than 

 was pyridoxine. 



The constitution of pyridoxamine and pyridoxal was established 

 by Harris et al.^^ (see page 300). 



Whereas pyridoxamine and pyridoxal had much the same growth- 

 promoting activity as pyridoxine for rats, some moulds and some 

 yeasts, for many of the lactic acid bacteria their activity was several 

 thousand-fold greater. ^^ The two compounds had little or no effect 

 on Saccharomyces cerevisiae, however, but stimulated the growth of 

 5. carlsbergensis to the same extent as did pyridoxine. ^^ Pyridoxal 

 and pyridoxamine had s/sth and 4/5th respectively of the growth- 

 promoting activity of pyridoxine in chicks. ^^ 



Pyridoxal and pyridoxamine are more labile than pyridoxine 

 (page 308), and readily react with other constituents of the medium ; 

 they are also destroyed by light. By using three different organisms 

 — L. helveticus, S. faecalis and S. carlsbergensis — E. E. Snell ^* was 

 able to distinguish between pyridoxine, pyridoxal and pyridoxamine ; 

 he found by this method that pyridoxal and pyridoxamine constituted 

 a high proportion of the vitamin Bg-active compounds in many natural 

 products. 



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