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Folate Synthesis and Metabolism in Plants and Prospects For Biofortification

^a Horticultural Sciences Dep., University of Florida, Gainesville, FL 32611
^b Food Science and Human Nutrition Dep., University of Florida, Gainesville, FL 32611

View larger version (22K): [in this window] [in a new window]   Fig. 1. Chemical structures of tetrahydrofolate and its C1-substituted derivatives. Natural folates occur mainly as polyglutamylated forms in which a -linked chain of up to about eight residues is added to the glutamate moiety. Numbered arrowheads mark potential sites of action of catabolic enzymes (see text). The removal of the polyglutamyl tail after the first glutamate (reaction 4, mentioned in the text) is not shown on this figure.

View larger version (25K): [in this window] [in a new window]   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).

View larger version (37K): [in this window] [in a new window]   Fig. 3. Transport of folates and precursors in plants. Letters indicate inferred transport steps (see text). Abbreviations are as in the legend of Fig. 2.