Pfizer Handbook of Microbial Metabolites 556 



moiety of folic acid have been isolated from non-microbial 

 species. This subject has been reviewed.^' '^ 



Labeled xanthopterin was converted to 5-formyl-5,6- 

 7,8-tetrahydropteroic acid by Enterococcus stei. Strepto- 

 coccus fecalis, E. coli and Pichia membranaefaciensr''' 

 Folic acid was not formed even when p-aminobenzoic acid 

 was added to the medium. Cell extracts of these micro- 

 organisms produced folic acid principally. 



The assembly of the three moieties of folic acid into the 

 complete molecule has been studied. Lactobacillus arabi- 

 nosus contains enzymes able to couple 2-amino-4-hydroxy- 

 pteridine-6-carboxaldehyde or the corresponding alcohol 

 with p-aminobenzoic acid.-^ 



OH OH 



I .. .CHO I . /CH2OH 





H2N H2N 



2-Amino-4-hydroxy- 2-Amino-4-hydroxy-6- 



pter'dine-6-carboxaldehyde hydroxy methylpteridine 



These pteridines are even more effective precursors in 

 their reduced forms. Many other pteridines tested were 

 not used. ATP (and Mg*"^) was required. Its role is un- 

 known, although phosphorylation of the alcohol of the 

 pteridine hydroxymethyl group might be necessary to 

 activate it for coupHng. 



p-Aminobenzoic acid was more effective than p-amino- 

 benzoylglutamic acid in this coupling reaction in E. coli,^^ 

 although Mycobacterium avium was able to use the pep- 

 tide.^" Apparently adenylo-p-aminobenzoic acid was an 

 intermediate in the latter organism (ATP and Co A were 

 required ) . 



The origin of p-aminobenzoic acid was considered in an 

 earlier section. It has been known for some time that the 

 anti-infective sulfonamide drugs function by interfering 



27 J. J. PfifFner and O. D. Bird, Ann. Rev. Biochem. 25 416-^19 

 (1956). 



27' F. Korte and Gotthard Synnatschke, Ann. 628 153 (1959). 



28 T. Shiota, Arch. Biochem. and Biophys. 80 155 (1959). 

 2«Gene M. Brown, Federation Proc. 18 19 (1959). 



^° H. Katunuma, Abstr. 32nd Congr. Japanese Biochem. Assoc, 

 Kyoto, July 1957. 



