118 III. OXIDATION AND METABOLISM 



Fatty acid dehydrogenases were localized in the mitochondria of rat liver 

 by Witter and collaborators.-'** The substrates in decreasing order of ac- 

 tivity included oleate, hexanoate, palmitate, 2-hexenoate, /3-hydroxyhex- 

 anoate, jS-hydroxybutyrate, and ,S-ketohexanoate. This dehydrogenase is 

 believed to carry the reaction beyond the stage of the Q:,/3-unsaturated acid. 

 Green and co-workers ^^^ reported that |3-hydroxybutyric dehydrogenase is 

 inhibited by 0.03 M-iodoacetate and by arsenite. This would suggest 

 that — SH groups are required for activity. Singer and Barron^*^ con- 

 firmed the fact that an — SH group is required in the activating protein for 

 /3-hydroxybutyric dehydrogenase. 



After reviewing all of the available evidence of Q:,/3-unsaturation, Breusch^ 

 states that "there also exists an enzyme system which, though perhaps less 

 important and quite mirelated to the enzyme system which brings about jS- 

 oxidation of fatty acids, catalyzes a,i8-dehydrogenation or hydrogenation of 

 fatty acids. The occurrence of a,/3-hydrogenation has been proved beyond 

 doubt; this proof is still outstanding for Q:,/3-dehydrogenation." 



(6) 9,10-Dehijdrogenases. a'. Preparation and Activation : Lang alone^*^ 

 and with co-workers^*^'-'*^ first prepared an active fatty acid dehydrogenase, 

 from the liver and the muscle of rats, in which the activity increases with 

 the length of the carbon chain of the substrate. It is specific for the higher 

 fatty acids. Adenylic acid was shown to be a co-dehydrogenase in muscle. 

 Inosinic acid and ATP were equally effective as coenzymes. These results 

 have been confirmed by a number of workers. ^"^'-^^ This enzyme is ap- 

 parently similar to that isolated from ox liver by Annau and co-workers.-^" 

 Both are activated by adenylic acid and by hypoxanthine;-^^ however, since 

 hypoxanthine is a more effective activator than is adenylate, Burton^^^ sug- 

 gests that the latter may exert its action through the hypoxanthine formed 

 from it. 



Champougny and LeBreton^"^--^- reported that a phosphorylation of the 

 fatty acids is necessary before the palmitic acid -^ palmitoleic acid or the 

 stearic acid -*■ oleic acid transformations can occur. Jacob and Pascaud-^^ 

 confirmed this finding, but believe that phosphorylation is catalyzed, not by 



2" R. F. Witter, M. Cottone, and W. J. Pories, Federation Proc, 12, 291-292 (1953). 



2« T. P. Singer and E. S. G. Barron, J. Biol. Chem., 157, 241-253 (1945). 



2« O. St. A. K. Lang, Z. physiol. Chem., 261, 240-248 (1939). 



2« K. Lang and H. Mayer, Z. physiol. Chem., 261, 249-252 (1939). 



2« K. Lang and H. Mayer, Z. physiol. Chem,., 262, 120-122 (1939). 



2« T. Fontaine, Bull. soc. chim. biol, 25, 286-292 (1943). 



250 E. Annau, A. Eperjessy, and O. Felszeghy, Z. physiol. Chem., 277, 58-65 (1942 



251 K. Burton, Nature, 161, 606 (1948). 



252 J. Champougny and E. LeBreton, Compt. rend. soc. biol., I4I, 45-48 (1947). 



253 A. Jacob and M. Pascaud, Compt. rend. soc. biol, 143, 1476-1478 (1949). 



