16 P-AMINOBENZOIC ACID 



technique, found that the enzyme can oxidize L-glutamic acid or p-amino- 

 benzoylglutamic acid in essentially the same length of time as is required 

 for pteroylglutamic acid oxidation, which occurs without any detectable 

 formation of either PABA or p-aminobenzoylglutamic acid. They interpret 

 this to mean that folic acid is not oxidized as such l>ut is hydrolyzed to 

 pteroic acid and glutamic acid, the latter being the agent responsible for the 

 reduction of the methylene blue. Accordingly, the enzyme must attack the 

 amide bond of folic acid. It would appear interesting, when one considers 

 the specificity of enzyme action, to investigate the behavior of this enzyme 

 toward other PABA conjugates, such as PAHA or the bound PABA re- 

 ported by Ratner.i^' '^ 



V. Biogenesis 



LEMUEL D. WRIGHT and PETER A. TAVORMINA 



The biogenesis of PABA is only one aspect of a much lai'ger subject, 

 that of the biogenesis of aromatic compounds in general. 



Quinic acid has been suggested as a precursor of aromatic compounds. 

 By the loss of three molecules of water this compound could yield jo-hy- 

 droxybenzoic acid. Quinic acid when administered to man does indeed yield 

 urinary hippuric acid.^' ^ Phenolic compounds are produced from quinic 

 acid by a variety of microorganisms including molds, yeast, and bacteria.^ 

 Quinic acid will promote growth of a Neurospora mutant with a requirement 

 for an aromatic compound, although it is only about 10 % as active for this 

 purpose as tryptophan.^ On the other hand, quinic acid is inactive in pro- 

 moting growth of any one of a variety of Escherichia coli mutants with 

 nutritive requirements for two to five aromatic compounds.^ 



meso-Inositol has been suggested by Fischer'' as a precursor of the aroma- 

 tic ring. Aromatization conceivably could result from a loss of three mole- 

 cules of water. No' actual experimental evidence indicating that PABA 

 originates from inositol has been published. 



12 S. Ratner, M. Blaiichard, A. D. Coburn, and D. K. Green, J. Biol. Chem. 155. 



689 (1944). 

 " S. Ratner, M. Blanchard, and D. E. Green, J. Biol. Chem. 164, 691 (1946). 



1 E. Lautemann, Ann. 125, 9 (1803). 



2 A. J. Quick, /. Biol. Chem. 92, 65 (1931). 



3 B. D. Davis, /. Biol. Chem. 191, 315 (1951). 



•« M. Gordon, F. A. Haskins, and TT. K. Mitchell, Proc. Xatl. Acad. Sci. U. S. 36, 



427 (1950). 

 5 II. O. L. Fischer, Harva/ Lcclares 40, 156 (1944-1945). 



