SATURATED FATTY ACIDS 



23 



o o 



CHs-C-S-CoA + CH3-CS-CoA 

 Condensation 



OH O 



CH3-C— CH^CS-CoA 



I 

 S-CoA 



Thiolysis 



O O 



II II 



CH3-CCH2-C-SCoA + HSCoA 



Hydrolysis 



O O 



CH3-C-CH2-COH + HS-CoA 

 The Role of Acetyl-CoA in the Synthesis and Hydrolysis of Acetoacetic Acid* 



molecules, and hydrolysis and resyn thesis are continually taking place. 

 For a further discussion of acetoacetate formation as related to oxidation, 

 the reader is referred to Chapter III (page 77). 



However, acetoacetate must likewise be regarded as an intermediate 

 product in the synthesis of long-chain acids from acetate. Thus, Chen, 

 Chapman, and Chaikoff^^ found that the carbonyl carbon of acetoacetate 

 is readily incorporated into long-chain fatty acids by the liver of the nor- 

 mal fed rats. The capacity for conversion of acetoacetate into fat was 

 found to be lost in the livers from normal fasted rats and from fed diabetic 

 rats. The injection of insulin into diabetic rats restored their ability to 

 synthesize long-chain fatty acids from acetoacetate. 



b. The Synthesis of Long-Chain Fatty Acids from Acetate. There are 

 a number of types of experimental evidence to prove that fatty acids 

 having chains longer than four carbons are synthesized by successive con- 

 densations of two-carbon fragments. For example, Rittenberg and 

 Bloch,^^ in 1945, demonstrated that the long-chain fatty acids, synthesized 

 by mice and rats after the feeding of labeled acetate, had the label uniformly 



«R. W. Chen, D. D. Chapman, and I. L. Chaikoff, /. Biol. Chem., 205, 383-393 

 (1953). 



