342 ANIMAL BIOCHEMISTRY 



PANTOTHENIC ACID 



This member of the B group of vitamins is the amide of a derivative 

 of butyric acid, called pantoic acid, and yg-alanine. Its only known 



CH3 



I 

 HOCH.>— C CH— CONHCHoCH.COOH 



1 1 



CH3 OH 



pantothenic acid 



role is as part of coenzyme A, whose structure is as shown. The left 

 portion of the molecule is a phosphorylated ADP, and the right portion 



NH;, 



H /O^ CH2OP-O-P OCH2C-CHOHCONHCH2CH,CONHCHpCH.,SH 



I { I ] ^ _ i. i. 



OH O CHo 



OH 0P03= 



coenzyme A 



is ^-mercaptoethylamine, probably formed by decarboxylation of cy- 

 steine. Coenzyme A is required in decarboxylations like those of pyru- 

 vate and a-ketoglutarate in the tricarboxylic acid cycle. It is involved 

 in the metabolism of hydrocarbon side chains, particularly those of 

 amino acids and fatty acids. See Chapters 19 and 20. This coenzyme 

 is quite essential to life. 



Pantothenic acid and coenzyme A are synthesized by green plants 

 and by many microorganisms. Animals cannot make pantothenic 

 acid, so this substance must be present in the diet to serve as a starting 

 point for coenzyme A. A mixture of |S-alanine and pantoic acid will 

 not suffice. Somewhat surprisingly, pantothenic acid is not lost by 

 hydrolysis in the gastrointestinal tracts of animals. 



The daily requirement of man is unknown. Recommendations ol 

 2.5 to 5.0 mg./lb. of feed have been made for poultry with the lower 

 figure for chickens and the higher value for ducks and turkeys. 



Most fruits and vegetables are rather low in pantothenic acid, but 

 yeast, meat, eggs, and milk are good sources. Pharmacological grades 

 of the calcium salt sell for .'$45/kg. and are used in enriching white 

 flours. 



