TRIGLYCERIDES AND FATTY ACIDS 91 



are absorbed. When they are administered in large doses, the normal 

 processes of /5-oxidation are exceeded, and co-oxidation comes into play as a 

 supplementary mechanism to rid the body of the fatty acids which cannot 

 be stored. Since lauric acid and higher acids can be partially deposited in 

 the tissues, two pathways of disposal are possible (/S-oxidation or storage), 

 and there is less requirement for co-oxidation. This interpretation has 

 been supported by the results of Stevens^^ in Carter's group. It was 

 found that /3-phenyl acids from Cg to Cy were excreted unchanged, for the 

 most part, but that those from Cg to C12 were excreted only to the extent 

 of about 20% as dienoic acids. The diacidogenic property of lauric acid 

 was markedly increased by substitution of the phenyl group in the jS- 

 position. This prevents storage, and thus necessitates increased emergency 

 oxidation in the form of co-oxidation. 



e. Miscellaneous Types of Oxidation. In addition to /S- and co-oxida- 

 tion, certain other types of oxidation have been suggested to explain the 

 catabolism of fatty acids in certain specific cases, llius, Clutterbuck and 

 Raper*^ showed that 7- and 5-oxidation, as well as /3-oxidation, could occur 

 in vitro when the ammonium salts of the longer-chain fatty acids were 

 oxidized with H2O2. There was no indication that a similar pattern might 

 obtain in vivo. In later work, these investigators^^ were unable to observe 

 any excretion of phenylsuccinic acid, IIOOC-CH(C6H5)-CH2-COOH, after 

 the subcutaneous administration of phenylhexanoic acid, HOOC.CHCCeHs)- 

 (CH2)4-COOH, to dogs. The former compound should have originated had 

 7-oxidation taken place. 



f . Desaturation Theory as a Method of Fatty Acid Oxidation. A number 

 of years ago, Leathes and collaborators^^ ~^^ advanced the hypothesis that 

 the first step in the oxidation of fatty acids involves their desaturation in the 

 liver. These misaturated fatty acids were shown to occur not only in the 

 phospholipid fraction but also in the neutral fat. Two main types of de- 

 hj^drogenation of fatty acids take place in the animal body ; namely, Q;,iS-de- 

 hydrogenation and 9,10-dehydrogenation. The relationship between de- 

 hydrogenation and oxidation of fatty acids has been reviewed by Breusch. ^ 



** C. M. Stevens, Thesis, Univ. Illinois, 1941; cited by H. E. Carter, Biol. Symposia, 

 5, 47-63 (1941), p. 60. 



^ P. W. Clutterbuck and H. S. Raper, Biochem. J., 19, 385-396 (1925). 



8" P. W. Clutterbuck and H. S. Raper, Biochem. J., 19, 911-914 (1925). 



" J. B. Leathes and L. Meyer-Wedell, /. Physiol, 38, xxxvii-xl (1909). 



8« E. L. Kennaway and J. B. Leathes, Lancet, 176, 95-98 (1909, I); Proc. Roy. Soc. 

 Med., 2, Part III, Palhol. Sect., 136-144 (1909). 



*' J. B. Leathes and H. S. Raper, The Fats, 2nd ed., Longmans Green, New York, 

 1925. 



