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Fig. 2. The tetrahydrofolate biosynthesis pathway in plants. The enzymes that have not yet been cloned from plants are underlined. ADC, aminodeoxychorismate; DHN, dihydroneopterin; DHNTP, dihydroneopterin triphosphate; Glu, glutamate; GTP, guanosine 5'-triphosphate; HMDHP, hydroxymethyldihydropterin; HMDHP-PPi, hydroxymethyldihydropterin pyrophosphate, pABA, p-aminobenzoate; PPi, pyrophosphate; Pi, inorganic phosphate; ADCS, aminodeoxychorismate synthase; ADCL, aminodeoxychorismate lyase; GTPCHI, GTP cyclohydrolase I; DHFR, dihydrofolate reductase; DHFS, dihydrofolate synthase; DHNA, dihydroneopterin aldolase; DHPS, dihydropteroate synthase; FPGS, folylpolyglutamate synthetase; HPPK, hydroxymethyldihydropterin pyrophosphokinase. Note that there are cytosolic and plastidial isoforms of FPGS as well as the mitochondrial enzyme shown (Ravanel et al., 2001).
