FAT METABOLISM 711 



' \I. KATTY ACID PORM OP 



AC rlCACID 



Acetic acid CH .COOB 



Propionic add CB ,CB ,.COOB 



Butyric add «'ll .CH,.CH t .COOB + 



Valeric add CB ,CH 1 .CH 1 .CB .COOB 



Oaproic add CB .CH f .CB .CB .CB .COOB 



Beptylic arid CB .CB .CB .CB .CB .CB .COOB 



(Mtiie acid <'ll .CB .CB .CB .CB .CB .OB .COOB 



Nbnoic add CB .CH,.Cfl .CB .CB .CB .CB .CB .COOB 



Heroic arid CH, . CH,.riI,;. CH, . CH,. ( 'H,. .CB,. CU, .('H 7 . CH ; .COOH + 



(From Dakin.) 



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

 a process of oxidation at the /8-C-atom could occur, since they * 

 unable to bring it aboul in the laboratory by the use of tin- ordinary 

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

 ing that hydrogen peroxide II 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 "ml their phenyl derivatives cai 

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

 a manner that tht two {or some multipU thereof) termial C-atoms an 

 removed at each successivi step in their decomposition. 



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

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

 tion of a )8-hydroxy acid, and second, the oxidation of this to a ketone 

 group. The mere presence, side by side, of (i hydroxyhutyric acid ami of 

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

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

 seem to show that the hydroxy acid may he derived from t ho ketone 



For example, when acetoacetlC 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 



0-hydroxy acid is added. A reversible reaction must therefore he capable 

 of occurring between these two substances, thus: 



reduct ion 



CB .CHOH.CB .•'noil « CB .<'<». en .COOB. 



oxidation 

 (/9-oxy butyric add) » ;, i • 



W'e know practically nothing as to the conditions determining whether 

 oxidation or reduction shall predominate, hut there are two Bignificanl 



facts that one should hear in mind: | 1 thai a plentiful supply of o\\ 



gen is n ssar\ for the oxidative process, and 2 that the presence 



rcadil\ oxidi/.ahlc material in the liver (e.g., carbohydrates may del 



mine the direction which llic reaction shall take. It is COmmonl] Said 

 that fats burn in the tire of carbohydrates, and it ma\ he that t ho tin- 



