POLYCARBOXYLIC ACIDS 307 



CH3-(CH2)8-COOH '- > HOOC-(CH2)8COOH 



oj-oxidation 



Capric acid Sebacic acid 



HOOC-rCHOe-COOH ■_ > HOOC-(CH2)4-COOH 



^-oxidation 

 Suberic acid Adipic acid 



Successive Stages in the Oxidation of Capric Acid by oj-Oxidation, Followed by Two Suc- 

 cessive ^-Oxidations" 



It is believed that co-oxidation proceeds under opposite conditions from 

 the usual /3-oxidation. Whereas fatty acids are believed to proceed by (3- 

 oxidation to the ketone bodies in the case of conditions which engender 

 ketonuria, diaciduria is fostered on high carbohydrate diets in the absence 

 of ketonuria. 



Although w-oxidation of fatty acids higher than C12 cannot ordinarily be 

 demonstrated, the oxidation of myristic (Cu) and stearic (Cis) acids by 

 this pathway can be shown when the usual /5-oxidation is blocked by the 

 presence in the a-position of a side-chain more than one carbon in length.-^ 

 Under these conditions, long-chain dicarboxylic acids have been demon- 

 strated in the urine. For a further discussion of co-oxidation, the reader 

 is referred to the preceding chapter. 



b. The Occurrence and Metabolism of Dicarboxylic Acids, (a) Intro- 

 duction. The most complete information in this category is available con- 

 cerning the metabolism of the four-carbon dicarboxylic acids ; of these acids, 

 the evidence at hand mainly concerns succinic acid. Oxalic acid, HOOC-- 

 COOH, the simplest dicarboxyhc acid, is oxidized to only a limited extent. 

 When administered in large amounts to the animal, it is toxic. It appears 

 in the urine of man to the extent of 20 to 40 mg. daily. ^^ Malonic acid, 

 HOOC • CH2 • COOH, is much more completely utilized, although it is not 

 generally regarded as a normally occurring metabolite. This acid may 

 act as an antagonist to ordinary tissue oxidation. The subject of 

 utilization of these and of other dicarboxylic acids has been reviewed 

 by Dakin^^ and by Flaschentrager." 



" P. Muller, Verhandl. Ver. schweiz. Physiol, 11, 8-9 (1937); Chem. Abst., 32, 6308 

 (1938); Physiol. Ahst.,22,Z4Q {\^?,1). 



^^ H. D. Dakin, Oxidations and Reductions in the Animal Body, 2nd ed., Longmans, 

 Green, London & New York, 1922. 



" B. Flaschentrager, Z. physiol. Chem., 159, 297-308 (1926). 



