234 Harland G. Wood 



These latter results are a good indication that the acetoacetate 

 was not metabolized via acetone, and the data as a whole 

 indicate that there was not an extensive interconversion of 

 acetone and acetoacetate. 



As noted previously Cg and C^ cleavage of methyl-labelled 

 acetone could account for the 1, 6-labelled glucose but not 

 for the high labelling in the 3, 4 positions of the glucose. It 

 appeared possible to test for a direct oxidation of acetone if 

 carbonvl labelled acetone were used. This is illustrated 

 below: — 



1 . Carbox vlation of acetone 



CH3 • C*0 • CH3 + COo ->CH3 • C*0 • CHg • COOH ->"CH3 • C*OOH"^ 



C-C-C*-C*-C-C 



2. C2 and C^ split 



CH3C*OCH3 -^ CH3C*00H+HC00H -> C-C-C*-C*-C-C 



3. Direct oxidation 



CH3 • C*0 • CHg-^'THg • C*0 • C00H"^CO-C*-CO-CO-C*-CO 



Only in case of direct oxidation should the tracer occur in 

 all positions of the glucose unit, and in addition it should be 

 highest in the 2, 5 positions. 



The results of this experiment (Sakami and Lafaye, 1951) 

 are shown below, as well as an experiment with a-labelled 

 lactate (Lorber et al., 1950a): — 



CH3ICOCH3 180 283 278 278 283 180 



CH3 • 13CHOH • COOHt 18 -27 05 05 .27 -18 



It is seen that the carbonyl labelled acetone gave a tracer 

 distribution pattern in the glycogen quite similar to a-labelled 

 lactate, i.e. the labelling was high in the 2, 5 positions. Thus 

 direct oxidation is indicated to occur. The only difference in 

 fThe experimental values are given as atoms per cent excess ^^C. 



