FAT METABOLISM 711 



(From Dakin.) 



For a long time it was difficult for chemists to understand how such 

 a process of oxidation at the /?-C-atom could occur, since they were 

 unable to bring it about in the laboratory by the use of the ordinary 

 oxidizing agents, but recently Dakin has removed the difficulty by show- 

 ing that hydrogen peroxide (H 2 2 ) oxidizes fatty acids just exactly in 

 this way. 



We may sum up the results of these experiments and observations by 

 stating that normal saturated fatty acids and their phenyl derivatives can 

 undergo oxidation, not only in the animal ~body, but also in vitro, in such 

 a manner that the two (or some multiple thereof) termial C -atoms are 

 removed at each successive step in their decomposition. 



But we must not be too hasty in concluding from these experiments that 

 the steps in the process are necessarily in the order of first, the produc- 

 tion of a /?-hydroxy acid, and second, the oxidation of this to a ketone 

 group. The mere presence, side by side, of /?-hydroxybutyric acid and of 

 acetone in the above experiments does not indicate which is the ante- 

 cedent of the other, and indeed there are several experimental facts that 

 seem to shoAv that the hydroxy acid may be derived from the ketone. 

 For example, when acetoacetic acid is added to minced liver and the 

 mixture incubated, /?-hydroxybutyric acid is formed (a reduction process), 

 although less usually the reverse action (oxidation) may occur when 

 /?-hydroxy acid is added. A reversible reaction must therefore be capable 

 of occurring between these two substances, thus: 



reduction 

 CH 3 .CHOH.CH 2 .COOH < - CH 3 . CO . CH 2 . COOH. 



oxidation 

 (j8-oxybutyricacid) > (acetoacetic acid) 



We know practically nothing as to the conditions determining whether 

 oxidation or reduction shall predominate, but there are two significant 

 facts that one should bear in mind: (1) that a plentiful supply of oxy- 

 gen is necessary for the oxidative process, and (2) that the presence of 

 readily oxidizable material in the liver (e.g., carbohydrates) may deter- 

 mine the direction which the reaction shall take. It is commonly said 

 that fats burn in the fire of carbohydrates, and it may be that the un- 



