230 Harland G. Wood 



j8-position and the ^^C was in the carboxyl-position. Following 

 this discovery it was possible to use serine as an indicator of 

 metabolism, i.e. it could be used to detect the formation of 

 "formate" from other labelled substrates. With this method 

 much information was obtained relative to the role of 1 -carbon 

 compounds in metabolism. Evidence has been obtained 

 with serine as an indicator, that "formate" is formed from the 

 a carbon of glycine (Sakami, 1949a), from the methyl groups 

 of choline (Sakami, 19496), and from the methyl groups of 

 acetone (Sakami, 1950). The demonstration that methyl 

 groups are converted to "formate" made it seem likely that 

 the methyl groups of methionine and choline might be 

 synthesized from formate by a reverse reaction. When this 

 idea was tested by Sakami and Welch (1950), it w^as found 

 that the synthesis occurred. 



In the present report the use of glycogen and serine as 

 indicators of intermediary metabolism of acetone will be 

 considered in some detail. In addition some recent studies 

 with the propionic acid bacteria will be reported since they 

 reinforce the idea that the C^-compounds have an important 

 role in metabolism. 



^ » 



Acetone Metabolism 



Although it has been recognized that acetone is formed by 

 animals, especially in diabetes mellitus, it has generally been 

 considered that acetone is formed by spontaneous decarboxy- 

 lation of acetoacetate and that once formed it plays no part 

 in metabolism but is excreted as such. This idea has been 

 held in spite of the fact that from time to time reports have 

 appeared which indicated that acetone is utilized (Schwarz, 

 1898; Rothkopf, 1936). The recent tracer experiments of 

 the Columbia group (Borek and Rittenberg, 1949; Price and 

 Rittenberg, 1950) served to refocus attention on this problem. 

 These workers demonstrated that rats utilize small amounts 

 of acetone efficiently and that it is oxidized in part to COo 

 and in part to "acetate." The latter was indicated by the 

 observed conversion of acetone to cholesterol and by the 



