Can complement an H.volcanii mutant strain that is thymidine auxotroph because it lacks the two dihydrofolate reductase genes encoded by hdrA and hdrB. (6S)-5,6,7,8-tetrahydrofolyl-(gamma-L-Glu)(n) + ATP + L-glutamate = (6S)-5,6,7,8-tetrahydrofolyl-(gamma-L-Glu)(n+1) + ADP + H(+) + phosphate (7,8-dihydropterin-6-yl)methyl diphosphate + 4-aminobenzoate = 7,8-dihydropteroate + diphosphate Cofactor biosynthesis; tetrahydrofolylpolyglutamate biosynthesis. Cofactor biosynthesis; tetrahydrofolate biosynthesis; 7,8-dihydrofolate from 2-amino-4-hydroxy-6-hydroxymethyl-7,8-dihydropteridine diphosphate and 4-aminobenzoate: step 1/2. In the N-terminal section; belongs to the folylpolyglutamate synthase family. In the C-terminal section; belongs to the DHPS family.