=C . CHa . CH.OH 



J. 



ANEURINE (thiamine) 



N=C— N=CH 



I I I 

 CH, . C C— CHj— N— C=C . CHa . CH,OH 



II II II 

 N— CH CH, SNa 



and 



N=C . NH, 



CH3.C C— CHa— N 



II II I 



N— CH CHO CHj SNa 



respectively. On treatment with iodine, a disulphide was obtained, 

 which, on reduction with tin and hydrochloric acid, was reconverted 

 into aneurine. This disulphide was antineuritic, having 60 to 70 % 

 of the activity of aneurine. 



Zima et al.,^'^ discussing the implications of this discovery, sug- 

 gested that aneurine and this disulphide might function as a bio- 

 catalyst for oxidations and reductions in the same way as do cysteine 

 and cystine. Aneurine was oxidised to the disulphide by treatment 

 with dilute hydrogen peroxide at pYi 7-5, whilst the disulphide was 

 reduced back to aneurine or to the corresponding thiol by cysteine or 

 glutathione, though not by ascorbic acid. 



So far, however, no conclusive evidence has been put forward to 

 indicate that the disulphide is ever formed in vivo. On the contrary, 

 it has been shown ^^ that cocarboxylase and its thiol form liberated 

 carbon dioxide from pyruvic acid at about the same rate, whereas the 

 disulphide pyrophosphate was inactive. The suggestion that vitamin 

 Bi is part of a redox system must therefore be rejected. 



This conclusion is supported by R. A. Peters,^* who found that 

 aneurine disulphide was at least as active as aneurine in the catatorulin 

 test, and that, in presence of SH-compounds, aneurine disulphide 

 pyrophosphate was able to effect the decarboxylation of pyruvic acid 

 by washed yeast. Cysteine, for example, was very effective, whereas 

 cystine was inert. Presumably, aneurine disulphide pyrophosphate 

 must first be reduced to aneurine by SH-compounds before it is active 

 in the catatorulin effect. 



Aneurine, a Catalyst Activating Pyruvic Acid 



Doubtless the final word has not yet been said as to the precise 

 r61e played by aneurine pyrophosphate in pyruvate metabolism, but 

 the most satisfactory hypothesis at the present time is undoubtedly 

 that of E. S. G. Barron, C. M. Lyman, M. A. Lipton and J. M. 

 Goldinger,'o ^j^q suggested that aneurine activates the pyruvic 



102 



