Asymmetric Citric Acid 253 



indicated by the results obtained previously by Buchanan, 

 Sakami, Gurin and Wilson (1945) and Weinhouse, Medes, 

 Floyd and Noda (1945) (Fig. 10) although they did not 

 isolate the citric acid. We have repeated the experiments 

 in our usual way with the use of [carboccy-^^Cyacetate and 

 [carbonyl-'^^C]-py ruY ate (Potter and Heidelberger, 1951). The 



(B) 



CH^COOH (W) 



Slices and Homogenates 



HOOCCOCH CH COOH 



COo + HOOCCH CH COOH 

 2 2 2 



KMnOj^ 



(B) 10$^ 90^ 



(w) 17% 83^ 



Fig. 10. Distribution of label in a-ketoglutarate from labelled 

 acetate and acetoacetate (Buchanan et al., 1945; Weinhouse 



et al., 1945). 



results indicated in Fig. 11 are somewhat surprising in that 

 the citric acid was not completely asymmetric, while the 

 tertiary carboxyl of the citric acid contained no isotope. 

 Some additional evidence bearing on this result was obtained 

 by studying the asymmetry of citric acid produced in vivo 

 (Potter, Heidelberger and Busch, 1951). When sodium 

 fluoroacetate is administered to rats there is an enormous 

 increase in the citric acid content of many tissues, and when 

 [carbOvCy-'^'^C]- acetate was administered to such an animal, 

 enough labelled citric acid could be isolated from the kidneys 

 of the rat to be degraded by the usual procedure. The very 



