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ANIMAL BIOCHEMISTRY 



CH2CONH2 



CH2CONH2 



NHOCCH2CH2 CH 



CH3 H CH2CH2CONH2 



vitamin B^2 



meats and especially liver are the only important dietary sources. 

 Human requirements are estimated to be only in the neighborhood 

 of a microgram daily. 



Although the function of this factor has been exceptionally difficult 

 to outline, vitamin B12 is believed to participate in the formation of 

 methyl groups. Apparently it is not essential to methyl transfer. 

 Whether methyl synthesis is concerned or not, the vitamin is required 

 for the production of red blood cells. 



Pernicious anemia is not strictly a dietary disease, but in human 

 beings and animals eating normally is due to improper absorption 

 of vitamin B^o. This rather common and serious abnormality thus 

 is a deficiency state but occurs only when the gastric juice is devoid 

 of a second factor. The missing component normally forms a complex 

 with the vitamin, permitting its absorption through the intestine. 

 Many isolation studies have failed so far in isolating and characterizing 

 a single material serving in the absorption of B^^- Apparently the 

 factor is present in very small amounts and may actually be more 

 than one substance. 



Injection of the vitamin by-passes the problem of intestinal absorp- 

 tion and cures the deficiency symptoms. Anemia is the most common 



