FATTY ACIDS 



129 



Fig. 7-1. Specificity of fatty acyl CoA dehydrogenases for sub- 

 states of different chain length (Crane et al. 1955). 



Ci6 fatty acids, and G (which is probably equivalent to butyryl CoA 

 dehydrogenase) is most active on C4 acids. The three enzymes can 

 thus effect the degradation of fatty acids up to sixteen carbons. More- 

 over, these workers discovered a fourth enzyme which is specific for 

 oxidation of the reduced forms of G, Yi, and Y2. The last, also a 

 flavoprotein, was designated an "electron transferring flavoprotein." 

 It presumably gives up electrons to some intermediate in the basic 

 electron transport system. 



In connection with the problem just posed above, a statement 

 of Hilditch (1952) is pertinent. Hilditch noted that the fatty acids of 

 more primitive plant and animal forms tended to represent a more 

 complex mixture, with a simpler mixture characteristic of more ad- 

 vanced organisms. This could represent the evolution of enzymes with 

 more specificity effecting more vigorous control over chain length in 

 fatty acids. Some authors, notably McNair (1941), have considered 

 that there is an increase in the molecular weight and the complexity 

 of the fatty acids during the course of evolution, a viewpoint which 

 is in part opposed to the idea of Hilditch, cited above. Goldovskii 

 (1960) has criticized both of McNair's premises: 



Owing to the great diversity of chemical reactions, the process of fatty 

 acid formation from its very inception must have led to a muhitude of 

 acids (polycondensation always leads to a number of polymer homol- 

 ogues). In fact, the simplest lower plants, in particular the algae and 

 fungi, already possess a complex equipment of fatty acids, including 

 high molecular ones. Nor can we agree with the idea of a rise in the 

 degree of unsaturation in the course of evolutionary development as a 

 whole, since even in the algae acids of a high degree of unsaturation 

 are formed. And, on the other hand, seed fats in the Compositae, the 

 members of which are generally taken to be at the summit of the 



