TRIGLYCERIDES AND FATTY ACIDS 93 



b' . Reactions in Which Q!,/3-Dehydrogenation Occurs : A large number of 

 instances may be cited in which a,(S-desaturation has been unequivocally 

 proved. 



(a') In the Oxidation of /8-Methylphenyl Fatty Acids. — Carter et al.^^ 

 have shown that the animal cannot demethylate phenyl-|S-methyl fatty 

 acids, and that they are excreted in part as a,|S-unsaturated fatty acids. 

 Thus, |S-methylphenylbutyric acid is catabolized as follows : 



-2H 



C6H5CH2CH(CH3)CH,-COOH > C6H5-CH2-C(CH3):CH-COOH 



/3-Methyl-7-phenylbutyric acid /3-Methyl-7-phenylcrotoiiic acid 



The Desatiiration of /3-]\Iethyl-7-Phenylbut3'ric Acid^^ 



In contradistinction to the dehydrogenation of the /3-methyl-7-phenyl- 

 butyric acid, Kuhn and Livada^^ failed to demonstrate a corresponding re- 

 action in the case of the next lower homologue. Thus, when /3-methylphen- 

 ylpropionic acid was given to rabbits, 30 to 35% was excreted in the urine 

 in free form, while 20 to 25% was coupled with glycine. The metabolism 

 was similar to that of /3-methylcinnamic acid in rabbits and dogs, although a 

 larger proportion was excreted in the free form when the unsaturated acid 

 was given. 



(b') In the Oxidation of Phenyl Fatty Acids. — Desaturation at the a,^- 

 position can likewise be observed in the case of misubstituted phenyl fatty 

 acids whose molecule does not contain a side chain methyl. Thus, Mazza^* 

 isolated phenylcrotonic acid after incubation of phenylbutyric acid with 

 survi\'ing liver. 



-2H 

 CeHsCHz-CHa-CHz-COOH > CeHsCHaCHiCHCOOH 



Phenylbutyric acid Phenylcrotonic acid 



The Desaturation of Phenj'lbutj-ric Acid^* 



(c') In the Removal of Water from /?-Hydroxy-Acids. — Snapper and 

 Griinbaum^^ showed that |S-phenyl-j8-hydroxypropionic acid is converted to 

 cinnamic acid by the removal of a molecule of water when the kidney is 

 perfused with the hydroxy acid. 



82 F. L. Breusch, Science, 97, 490-492 (1943). 

 " J. H. Quastel, Biochem. J., 20, 168-194 (1926). 



" F. Zetzsche, E. Luscher, H. E. Meyer, H. Overbeck, and H. Lindlar, Ber., 71, 1088- 

 1093, 1516-1521, 2095-2102 (1938). 



'^ F. L. Breusch and E. Ulusoy, Arch. Biochem., 11, 489-498 (1946). 



s« H. E. Carter, E. Osman, H. Levine, and S. Gamm, J. Biol. Chem., 128, xiii (1939). 



" R. Kuhn and K. Livada, Z. physiol. Chem., 220, 235-246 (1933). 



«8 F. P. Mazza, Arch. sci. biol. (Italy), 21, 320-331 (1935). 



" I. Snapper and A. Grunbaum. Chinese J. Physiol., 15, 301-308 (1940). 



