570 THE BIOCHEMISTRY OF B VITAMINS 



diet, deficient in riboflavin, is also corrected by pteroyldi-y-glutamyl- 

 glutamic acid. 57a 



Pteroyldi-y-glutamylglutamic acid is just as effective on a molar basis 

 as folic acid in promoting growth and hemoglobin formation in 

 chicks. 17 - 59, 60 Early work indicated that, while folic acid was effective 

 alone, chicks required a supplementary factor for the utilization of the 

 pteroyltriglutamic acid. This factor could be replaced by 5- or 4-pyri- 

 doxic acid (p. 657) or their lactones (a- or /?-pyracin) . 8 °- 82 4-Pyridoxic 

 acid was the more effective of the two isomers. Attempts 59, 60 to confirm 

 this supplementary effect have not been successful, with the exception 

 of a single experiment involving a comparison between two groups of 

 six chicks each. 83 In hemorrhagic anemia in hens, either pteroyltriglutamic 

 acid or 4-pyridoxic acid, or more effectively, a combination of the two 

 compounds, was reported to exert a beneficial action in hastening the 

 regeneration of hemoglobin. 84 The yield of folic acid, determined with 

 Streptococcus faecalis R from an incubation mixture of pteroyltriglu- 

 tamic acid and chicken liver, increased twofold on supplementing the 

 mixture with 4- or 5-pyridoxic acid. 85 



N-Pteroyldi-y-glutamylglutamic acid is also effective in replacing 

 folic acid in stimulating the Rous sarcoma virus in folic acid-deficient 

 chicks. 77 



This pteroyltriglutamic acid on a molar basis is just as effective as folic 

 acid in maintaining the concentration of microbiologically active forms of 

 folic acid in the blood of turkey poults on a folic acid-deficient diet. 61 

 The triglutamate, however, is more effective than folic acid in increasing 

 the blood concentrations of conjugates of folic acid which are hydrolyzed 

 by chicken pancreas. 61 



A conjugase preparation from chicken pancreas 86 hydrolyzes N-pteroyl- 

 di-y-glutamylglutamic acid as well as N-(p-aminobenzoyl)di-y-glutamyl- 

 glutamic acid and produces one molecule of glutamic acid for each 

 carboxyl group liberated. 87 Assay with S. faecalis R of the reaction mix- 

 ture resulting from the action of the enzyme preparation on the pteroyl- 

 triglutamic acid indicated the liberation of activity equivalent to one folic 

 acid for each glutamic acid. These results suggest that the triglutamate 

 is hydrolyzed only to the diglutamate, which is approximately as active 

 as folic acid for S. faecalis R. Since one equivalent of glutamic acid shows 

 an inhibitory effect on the enzymatic reaction, it is suggested that the 

 glutamic acid formed may prevent the reaction from going to completion. 87 



The pteroylhexaglutamylglutamic acid, vitamin B c conjugate, possesses 

 on a molar basis only about one per cent of the activity of folic acid for 

 the two bacteria, Lactobacillus casei and Streptococcus faecalis R, which 

 are commonly used for the assay of folic acid. 12 On the other hand, both 



