The nutritional equivalence of pantothenate and p-aminobenzoate for the growth of Bacterium linens.

Knowledge concerning the function of paminobenzoate in biological systems has been derived largely by the use of specificcompetitive inhibitors. Thus, the reversal of either sulfanilamide or 2-chloro4-aminobenzoate inhibition by methionine and other amino acids (Lampen et al., 1946; King et al., 1948; Strandskov, 1947; Winkler and DeHaan, 1948), by pteroylglutamic acid (Nimmo-Smith et al., 1948; Jukes and Stokstad, 1948), and by certain purines and pyrimidines (Cutts and Rainbow, 1949; Lampen and Jones, 1947) has been considered evidence that p-aminobenzoate functions in the synthesis of these metabolites. Similarly, the data of King et al. (1948) imply that paminobenzoate also functions in the synthesis of pantothenate since pantothenate effectively antagonized the inhibition of 2-chloro4-aminobenzoate in a mutant of Escherichia coli. High levels of pantothenate also partially satisfied the p-aminobenzoate requirements of a mutant of Saccharomyces cerevisiae (Pomper, 1952). The function of p-aminobenzoate in the synthesis of folic acid or pteroylglutamic acid has been attributed to its incorporation into the pteroylglutamic acid molecule (Angier et al., 1946). Whether p-aminobenzoate is involved indirectly through folic acid or a like metabolite in the synthesis of amino acids, purines, etc., or whether it has a separate catalytic role in the synthesis of metabolites other than pteroylglutamate has not been decided conclusively. From a nutritional study of 25 strains of Bacterium linens, it was observed (Purko et al., 1951) that one strain (no. 456) is able to grow when either pantothenate or p-aminobenzoate is present. While an interaction between p-aminobenzoate and pantothenate may be indicated from the use of 2-chloro4-aminobenzoate by