208 THE BIOCHEMISTRY OF B VITAMINS 



function for the vitamin appeared in a recent preliminary report. 333 The 

 livers from day-old chicks hatched from eggs laid by hens whose diet 

 contained no "animal protein" were used as a source of tissue deficient in 

 vitamin Bi 2 . These livers were incapable of liberating folic acid from 

 pteroylheptaglutamic acid. However, the addition of crystalline vitamin 

 B12 initiated conjugase activity. This would indicate that vitamin B 12 , 

 or a derivative of it formed by the liver cells, is a cofactor for some 

 reaction in the process by which the folic acid conjugate is degraded. The 

 same reaction, or one related to it chemically, may very well be one of 

 the essential steps involved in the conversion of folic acid and p-amino- 

 benzoic acid to their active coenzymes. 



The particular reaction (s) catalyzed by B i2 may be of an oxidative 

 type if the molecular structure of the vitamin is indicative of its mode 

 of functioning. All other metallo-porphyrin enzymes mediate oxidative 

 reactions (p. 151). A similar mechanism for vitamin Bi 2 action may be 

 anticipated if further investigation establishes its structure to be that of 

 a typical porphyrin. 



There is some metabolic relationship, either direct or indirect, between 

 this vitamin and ascorbic acid (or other reducing compounds). These 

 agents alter the nutritional requirements of lactobacilli to such an extent 

 that in their presence the organism can no longer be demonstrated to 

 require an exogenous supply of vitamin B i2 or the desoxyribosides. 325 - 334 

 The ascorbic acid-vitamin B i2 effect in microorganisms may be related 

 to the synergistic effects of liver extracts and vitamin C in the treatment 

 of pernicious anemia. 335 



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