344 ANIMAL BIOCHEMISTRY 



loss of hair and weight, edema, and skin lesions appear, with changes 

 in posture and gait. Death may result. Heating egg white destroys 

 the avidin and prevents the so-called egg-white injury. 



FOLIC ACID 



This vitamin has been known by a variety of names, most of which 

 are no longer used. The structure confirmed by synthesis is shown. 



H2N^Ns^N^ GOOH 



N. 



^^— CH2— NH— <^ ^— CONHCHCH2CH2COOH 

 OH 



folic aciil 



An amide of p-aminobcnzoic acid and glutamic acid is attached to 

 the left-hand portion of the molecule called a pterin. Some bacterial 

 species require a supply of /?-aminobenzoic acid, which is needed in 

 turn in forming folic acid. There is limited indirect evidence that 

 p-aminobenzoic acid may play other roles in certain microorganisms. 

 There is a series of these folic acid vitamins differing only in the 

 number of attached glutamic acids, which may range to at least 

 seven units. Folic acid itself is probably reduced to tetrahydrofolic 

 acid, which actually participates in the transfer of one carbon unit 

 in various metabolic processes, for example, serine-glycine intercon- 

 versions. (See page 466.) 



H 



H.N^Nx^Ns^Ho COOH 



N^/^M/^H— GHo— NH— ^ ^— CONHCHCH2CH2COOH 



tetrahydrofolic acid 



While this vitamin (folic acid) is certainly indispensable, its wide 

 distribution makes deficiencies somewhat rare. Moreover, rapid syn- 

 thesis by intestinal bacteria provides an additional supply, making it 

 difficult and almost unnecessary to assign daily allowances. None have 

 been fixed as yet. Folic acid is relatively abundant in leafy vegetables, 

 beef, and many seeds and grains, especially wheat. 



This factor is useful in treating certain abnormalities of the blood, 

 primarily macrocytic anemias with reduced numbers and oversized red 



