100 III. OXIDATION AND METABOLISM 



phenylpropanol, but this appears unlikely. The greatest proportion (60%) 

 of the cinnamyl alcohol was oxidized only at the alcohol group, to form 

 Q:,i3-dehydrophenylpropionic acid, CeHs-CHrCH-COOH, without a,^- 

 hydrogenation or with the addition of hydrogen to the double bonds to 

 form j8-phenylpropionic acid, C6H5-CH2-CH2-COOH. 



However, when an ethyl group was present in the cinnamyl alcohol, no 

 a!,/3-saturation occurred, but only the oxidation of the alcohol group to the 

 unsaturated acid. 



C6H5CH:C(C2H5)CH20H > C6H5CH:C(C6H5)-COOH 



Ethylcinnamyl alcohol a-Ethylcinnamic acid 



Fischer and Bielig^^'' Ukewise demonstrated that the feeding of ketones 

 containing Q:,|3-unsaturated bonds, such as C6H5-CH:CH-CO-CH2-CH3, 

 may result only in the production of a saturated ketone, CeHs • CH2 • CH2 • - 

 CO • CH2 • CH3 • , or in the formation of a saturated secondary alcohol, CeHs-- 

 CH2-CH2-CHOH-CH2-CH3. It was likewise observed that a certain i 

 amount of oxidation occurred on the benzene ring, since p-HO-C6H4-CH2--j 

 CH2 • CO • CH2 • CH3 was obtained. 



(b) Hydrogcnation of 9,10-Unsaturated Compounds. A number ofj 

 workers' ''^~^^" have demonstrated that unsaturated dietary fats may be par- 

 tially hydrogenated before they are deposited in the animal body. Since! 

 most of these fats have fatty acids with unsaturation in the 9,10-position, it 

 is evident that the hydrogenation involves the 9,10-linkage. Hilditch andj 

 Pedelty^^^ reported that oleoglycerides may be transformed to stearoglyc- 

 erides by enzymic hydrogenation. Zeller and Maschek'^'* isolated an en- 

 zyme from pumpkin seedlings which has the capacity to bring about the] 

 saturation of unsaturated acids. 



(S) Enzyme Systems Involved in Fat Oxidation 



Several oxidation systems for fatty acids have been widely investigated, 

 and considerable information is available as to the mechanism of their ac- 1 

 tion. One of these systems, which acts on saturated and unsaturated fatty 

 acids, is the so-called fatty acid oxidase system. The second enzyme sys- 



1^ T. P. Hilditch, The Chemical Constitution of Natural Fats, 2nd ed., Wiley, New 

 York, 1947, 



1" D. Rittenberg and R. Schoenheimer, /. Biol. Chem., 117, 485-490 (1937). 



130 J. A. Lovern, Biochem. J., 30, 2023-2026 (1936). 



131 A. Banks and T. P. Hilditch, Biochem. J., 26, 298-308 (1932). 



1" T. P. Hilditch and H. E. Longenecker, Biochem. J., 31, 1805-1819 (1937). 

 1" T. P. Hilditch and W. H. Pedelty, Biochem. J., 34, 971-979 (1940). 

 "4 A. Zeller and F. Maschek, Biochem. Z., 312, 354-369 (1942). 



