Acetone Metabolism 233 



The resulting labelled "formate" would then yield 1, 6 labelled 

 glucose as previously discussed and would be mixed with 

 glucose formed simultaneously from the "acetate" but this 

 part of the glucose would be equally labelled in the 1, 2, 5, 6 

 positions and would not mask the detection of "formate." 

 However, the formation of labelled "formate" from acetone 

 would not account for the high labelling in the 3, 4 positions 

 and it therefore was considered that there might be a direct 

 conversion of the acetone to "pyruvate." 



C*H3-COC*H3 -> ''C*H3-C0C*00H" -> C*-CO-C*-C*-CP-C* 



In fact this type of labelled pyruvate would in itself yield a 

 glucose that would fit the results since from it a glucose would 

 presumably be formed which would be labelled high in both 

 the 1, 6 and 3, 4 positions. 



Sakami's first tests were concerned with the hypothesis that 

 the acetone was split to "formate" and "acetate." For this 

 test he used serine as the indicator. The serine was isolated 

 from the liver protein (Sakami, 1950) and was degraded. 

 The results of this experiment, as well as one in which labelled 

 formate was given (Sakami, 1948), are shown below: — 



HOCH2 - CH(NH2) - COOH 

 420 15 18 



Hi^COOH 377 20 4 



14CH3-C0 14CH3 420 15 18 



Since the labelling of the ^-carbon of serine in the two experi- 

 ments was of the same order of magnitude and the concen- 

 tration and activity of the administered formate and acetone 

 were roughly the same, the indications are that the Cg and C^ 

 pathway of acetone metabolism may be of major quantitative 

 significance. 



When C*H2-CO*C*H2-COOH was administered in similar 

 concentration, the labelling in the serine was much lower 

 (Sakami, 1950):— 



HOCH2 - CH(NH2) - COOH 

 14CH3CO14CH2COOH 15 7 4 



