The Biosynthesis of Folic Acid. Iii. Enzymatic Formation of Dihydrofolic Acid from Dihydropteroic Acid and of Tetrahydropteroylpolyglutamic Acid Compounds from Tetrahydrofolic Acid.

Although dihydrofolic acid can be formed enzymatically, in the presence of adenosine triphosphate, from 2-amino4-hydroxy-6hydroxymethyldihydropteridine and p-aminobenzoylglutamic acid (3, 4), Brown, Weisman, and Molnar (4) have postulated that dihydropteroic acid, instead of p-aminobenzoylglutamic acid, is the normal intermediate in dihydrofolate synthesis in Escherichia coli. They have presented evidence which indicates that dihydrofolate formation proceeds by the following enzymatic reactions.