Table 4.
Primary, Intermediate, and Secondary Metabolic Pathways in Citrus
| Pathway | Enzymatic Activity | EC reaction | Unigenesa | ESTsb |
| Glycolysis | Hexokinase | 2.7.1.1 | 4 (2)c | 6 (4)d |
| Glucose-6-phosphoisomerase | 5.3.1.9 | 6 (1) | 16 (1) | |
| 6-Phosphofructokinase | 2.7.1.11 | 10 | 35 | |
| Fructose 1,6-biphosphate aldolase | 4.1.2.13 | 12 (7) | 71 (9) | |
| Triose phosphate isomerase | 5.3.1.1 | 8 (1) | 22 (1) | |
| Glyceraldehyde 3-P dehydrogenase | 1.2.1.12 | 8 (2) | 52 (8) | |
| Phosphoglycerate kinase | 2.7.2.3 | 6 (1) | 15 (3) | |
| Phosphoglycerate mutase | 5.4.2.1 | 1 | 5 | |
| Enolase | 4.2.1.11 | 7 (4) | 28 (5) | |
| Pyruvate kinase | 2.7.1.40 | 10 (1) | 69 (9) | |
| Tricarboxylic acid cycle (Krebs cycle) | Citrate synthase | 4.1.3.7 | 2 | 13 |
| Aconitase | 4.2.1.3 | 6 (1) | 31 (1) | |
| Isocitrate dehydrogenase | 1.1.1.42 | 3 | 59 | |
| a-Ketoglutarate dehydrogenase complex | 1.2.4.2 | No hits | No hits | |
| Succinyl-CoA synthetase | 6.2.1.5 | 2 | 14 | |
| Succinate dehydrogenase | 1.3.5.1 | 2 | 20 | |
| Fumarase | 4.2.1.2 | 3 (2) | 30 (5) | |
| Malate dehydrogenase | 1.1.99.16 | 4 | 24 | |
| Oxidative/nonoxidative pentose phosphate pathway | Glucose 6-P-1-dehydrogenase | 1.1.1.49 | 4 | 4 |
| 6-Phosphogluconolactonase | 3.1.1.31 | 2 | 10 | |
| 6-Phosphogluconate dehydrogenase | 1.1.1.44 | 15 | 47 | |
| Ribose-5-P isomerase | 5.3.1.6 | 3 | 12 | |
| Ribose-5-P 3-epimerase | 5.1.3.1 | No hits | No hits | |
| Transketolase | 2.2.1.1 | 3 (2) | 22 (11) | |
| Transaldolase | 2.2.1.2 | 4 (2) | 20 (17) | |
| Aromatic amino acid biosynthesis | 3-Deoxy-D-arabino-heptulosonate 7-P synthase | 4.1.2.15 | No hits | No hits |
| 3-Dehydroquinate synthase | 4.2.3.4 | 2 | 2 | |
| 3-Dehydroquinate dehydratase | 4.2.1.10 | 2 | 2 | |
| Shikimate 5 dehydrogenase | 1.1.1.25 | 1 | 14 | |
| Shikimate kinase | 2.7.1.71 | 7 | 10 | |
| 5-Enolpyruvoylshikimate 3-P synthase | 2.5.1.19 | No hits | No hits | |
| Chorismate synthase | 4.2.3.5 | 2 | 2 | |
| Chorismate mutase | 5.4.99.5 | 1 | 1 | |
| Prephenate dehydratase | 4.2.1.51 | 3 | 5 | |
| Prephenate dehydrogenase | 1.3.1.12 | 2 (1) | 18 (2) | |
| Aromatic amino acid transaminase | 2.6.1.57 | 6 | 18 | |
| Anthranilate synthase | 4.1.3.27 | 6 (1) | 46 (29) | |
| Anthranilate phosphoribosyl transferase | 2.4.2.18 | 4 | 6 | |
| Phosphoribosylanthranilate synthase | 5.3.1.24 | No hits | No hits | |
| Indol-3-glycerol phosphate synthase | 4.1.1.48 | 4 (2) | 6 (2) | |
| Trp synthase | 4.2.1.20 | 8 (1) | 30 (1) | |
| Phe ammonia-lyase | 4.3.1.5 | 5 | 13 | |
| Cinnamate 4-hydroxilase | 1.14.13.11 | 1 | 3 | |
| 4-Coumarate coenzyme A ligase | 6.2.1.12 | 10 (1) | 40 (1) | |
| Flavonol biosynthesis | Naringenin chalcone synthase | 2.3.1.74 | 6 | 48 |
| Chalcone isomerase | 5.5.1.6 | 3 | 17 | |
| Flavanone 3-hydroxylase | 1.14.11.9 | 2 (1) | 12 (1) | |
| Flavonol 3-hydroxylase | 1.14.13.21 | 6 | 7 | |
| Flavonol synthase | No E.C. | 2 | 19 | |
| Flavonol 3-O-glucosyltransferase | No E.C. | No hits | No hits | |
| Flavonoid biosynthetic pathway: anthocyanin biosynthesis | Dihydroflavonol 4-reductase | 1.1.1.219 | No hits | No hits |
| Leucoanthocyanidin dioxygenase | NoE.C. | 2 | 33 | |
| UDP-flavonol 3-O-glucosyltransferase | 2.4.1.- | No hits | No hits | |
| Anthocyanin 5-O-glucosyltransferase | NoE.C. | 2 | 9 | |
| Anthocyanin 5-aromatic acyltransferase | 2.3.4.153 | 6 | 36 | |
| Anthocyanin permease | NoE.C. | No hits | No hits | |
| Proanthocyanidin biosynthesis | Anthocyanidin reductase | 1.3.1.77 | No hits | No hits |
| Leucoanthocyanindin reductase | No E.C. | 2 (1) | 4 (2) | |
aNumber of citrus unigenes annotated with the emzymatic activiy
bTotal number of ESTs corresponding with the unigenes
The number between brackets indicates the number of unigenes (c) or ESTs (d) that are first reported in this work