^-AMINOBENZOIC ACID 



with haemolytic streptococci or pneumococci. Five other com- 

 pounds, 3-methyl- and 2-chloro-4-aminobenzoic acid, 4-amino-iso- 

 phthalic acid, 4-(4'-aminobenzamido)-benzoic acid and ethyl 4-amino- 

 benzoate, completely antagonised the growth-inhibitory action of 

 sulphanilamide.io 



References to Section 12 



1. J. O. Lampen and W. H. Peterson, Arch. Biochem., 1943, 2, 443. 



2. R. D. Housewright and S. A. Koser, /. Infect. Dis,, 1944, 76, 113. 



3. E. F. MoUer and K. Schwartz, Ber. 1941, 74B, 1612 ; O. Dann and 



E. F. Moller, Chem. Ber., 1947, 80, 21. 



4. S. Rosenthal, H. Bauer and E. Elvove, U.S. Publ. Health Rep., 



1939, 54, 13 17. 



5. J. Hirsch, Science, 1942, 96, 140. 



6. E. Auhagen, Z. physiol. Chem., 1942, 274, 48. 



7. O. H. Johnson, D. E. Green and R. Pauli, /. Biol. Chem., 1944, 



153, 37. 

 ya. A. T. FuUer, C. R. Harington, R. Pitt Rivers and J. M. L. Stephen. 

 /. Chem. Soc, 1948, 241. 



8. A. R. Martin, F. L. Rose and G. Swain, Nature, 1944, 164, 639. 



9. D. Wyss, M. Rubin and F. Strandskov, Proc. Soc. Exp. Biol. Med., 



1943, 52, 155. 

 10. A. R. Martin and F. L. Rose, Biochem. J., 1945, 39, 91. 



13. FUNCTION OF p-AMINOBENZOIC ACID 



The relationship between _/)-aminobenzoic acid and snlphanilamide 

 and the significance of the Woods-Fildes theory have already been 

 discussed (page 546). If this theory is correct, ^-aminobenzoic acid 

 and sulphanilamide compete with one another for an enzyme system 

 essential for the activity of the bacterial cell. This enzyme is prob- 

 ably concerned with the synthesis of folic acid (page 515), since 

 pteroylglutamic acid non-competitively reverses the antibacterial 

 action of sulphanilamide. 



^-Aminobenzoic acid, however, is not the only antagonist for the 

 sulphonamides for, in presence of sub-optimal amounts of ^-amino- 

 benzoic acid, adenine, guanine, xanthine and hypoxanthine nullified 

 the bacteriostatic effect of sulphanilamide against L. arabinosus and 

 L. pentosus} Any of these purines antagonised the effect of sul- 

 phanilamide on L. pentosus or L. helveticus in the absence of ^-amino- 

 benzoic acid. With L. pentosus, the effect of the purines appeared 

 to depend on the presence of a growth factor that was not ^-amino- 

 benzoic acid. In the absence of ^-aminobenzoic acid, the growth of CI. 

 acetohutylicum was stimulated by adenine, guanine, xanthine and 

 uracil. 2 



562 



