TRIGLYCERIDES AND FATTY ACIDS 95 



ketone bodies and the qualitative distribution between the acetoacetate and 

 j8-hydroxybutyrate fractions in the urine of fasting rats were identical, ir- 

 respective of whether butyric acid or an isomolecular amount of crotonic 

 acid was fed as their sodium salts. Crotonic acid was sho^vn to yield a 

 slightly greater amount of ketone bodies than does butyric acid, with hver 

 slices, ^"2 or when oxidized by the cyclophorase liver system of Grafflin and 

 Green. '"^ It has been reported that Q:,/3-hexenoic acid (CH3-CH2-CH2-CH:- 

 CHCOOH)^'' and sorbic acid (CH3-CH:CHCH:CH-COOH)22 produce the 

 same amounts of ketone bodies as does caproic acid when fed to fasting 

 animals. In addition, Cohen^"- demonstrated that sorbic acid produces 

 ketone bodies with liver slices, while Grafflin and Green ^"^ found that sorbic 

 acid is metabolized by the kidney cyclophorase system, and that trans- 

 A,Q:,iS-hexenoic acid and sorbic acid are metabolized by rabbit liver prep- 

 arations in a manner similar to the effect of caproic acid. The metabolism 

 of Q:,/3-pentenoic acid (CH3-CH2-CH:CH-COOH), cis~ and trans'a,l3- 

 hexenoic acid and sorbic acid were all found to give rise to considerable 

 amomits of acetoacetate. 



Jowett and QuasteP^ are of the opinion that crotonic acid is not an in- 

 termediate of butyric acid oxidation, although it is also convertible to 

 ketone bodies. On the other hand, Cohen ^o- suggested that a definite chem- 

 ical grouping is required for oxidation by the so-called j8-oxidase system. 



O 



The skeleton group has the basic structure, — CH : CHC — , which would 

 fit in well with the theory that dehydrogenation precedes oxidation. Lip- 

 mann and Perlmann^"^ suggested that an intermediary desaturation may be 

 associated with a phosphorylation, which would result in oxidation ac- 

 cording to the following scheme : 



-2H 



— CH.CH— H0P0,H2 > — C(0P03H):CH (1) 



H2O 

 — C(OP03H2):CH > ~C(:0)CH2— H3PO4 + 11 Kg cal. (2) 



Suggested Mechanism by Which Unsaturated Linkages Function in the Oxidation of 



Fatty Acids'" 



Reaction (2) occurs by virtue of the energy-rich phosphate bond which is 

 formed in reaction (1 ) . While it is uncertain to what degree the unsaturated 

 fatty acids play a role in the oxidation of fatty acids, it is certain .that the 



!<"» P. P. Cohen, /. Biol. Chem., 119, 333-346 (1937). 



•03 A. L. Grafflin and D. E. Green, J. Biol. Chem., 176, 95-115 (1948). 



"•* F. Lipmann and G. E. Perlmann, Arch. Biochem., 1, 41-50 (1942), 



