Folate biosynthesis in higher plants. (a) Chemical structure of folate. (b) The biosynthesis involves chloroplastidic, mitochondrial, and cytosolic steps. p-ABA, p-aminobenzoate; ADC, aminodeoxychorismate; AL, ADC lyase; AS, ADC synthase; DFR, Dihydrofolate reductase; DFS, Dihydrofolate synthase; DHM, dihydromonapterin; DHN, dihydroneopterin; DHN-P, dihydroneopterin phosphate; DHNTP, dihydroneopterin triphosphate; DPS, Dihydropteroate synthase; DHNTP-PPase, DHNTP-diphosphatase; DHNA, DHN aldolase; FPGS, Folylpolyglutamate synthase; GCHI, GTP cyclohydrolase I; Glu, L-glutamate; HMDHP, hydroxylmethyldihydropterin; HPK, HMDHP pyrophosphokinase.