ANEURINE (thiamine) 



oxidation and the amount used under conditions optimal for dismuta- 

 tion, were determined for gonococci, Streptococcus haemolyticus and 

 for several strains of Staphylococcus aureus. Only with the strain of 

 S. haemolyticus and with one strain of S. aureus was the rate of pyruvic 

 acid disappearance greater in the absence than in the presence of 

 oxygen. In rat tissues also anaerobic metabolism was lower than 

 aerobic metabolism, whilst in goose erythrocytes, pyruvic acid was 

 not utilised at all in the absence of oxygen. Further results by 

 E. S. G. Barron and C. M. Ljnnan ^^ confirmed these views. They 

 showed that kidney slices from normal rats produced an increased 

 amount of glucose when incubated with pyruvate, whereas kidney 

 slices from vitamin Bi-deficient rats did not give such a marked 

 increase imtil aneurine was added. Heart slices from vitamin B^- 

 deficient rats produced less citrate from pyruvate and oxaloacetate 

 than did normal heart slices. In this instance, however, no increase 

 occurred on addition of aneurine, due to a failure to phosphorylate 

 the aneurine during the short time of incubation. This evidence 

 strengthens the view that aneiuine catalyses not only the oxidation 

 and dismutation of pyruvate, but other reactions involving it. It is 

 therefore suggested that cocarboxylase is an integral part of an 

 enzyme system concerned with the activation of pyruvate, enabling 

 it to take part in a number of reactions. 



The problem was also studied by K. G. Stern and J. L. Melnick, ^^ 

 who showed that pyruvic acid was not decarboxylated via the " Langen- 

 beck cycle ", i.e. by combination with cocarboxylase to form a catalytic- 

 ally active substituted imino acid : 



CH3 . CHO \ /^ CH3 . C . C00H\ CH3 . CO . COOH + R . NH, 



N.R 

 CH3.CO.COOH/'\ CH3.CH:NR t/ \COa 



and confirmed Lipmann's results on the reduction of aneurine. They 

 pointed out, however, that no evidence was advanced by Lipmann to 

 support his view that aneurine acts as a reversible oxidation-reduction 

 system in the same way as pyridine coenzyme. Stern and Melnick 

 claimed that dihydro -aneurine was devoid of biological activity, but 

 that dihydro-cocarboxylase was as active as the oxidised form in both 

 the polyneuritic pigeon and in yeast. In a re-investigation of the 

 problem, however, they found ^* that the supposed biological activity 

 of reduced cocarboxylase was due to the presence of traces of un- 

 changed coenzyme. Fully reduced cocarboxylase, like reduced 

 aneurine, had no biological activity. 



Barron and Lyman and their collaborators ^^ showed that cocar- 

 boxylase was more resistant than aneurine to the action of oxidising 



100 



