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Figure 2 | Kinetoplastid Biology and Disease

Figure 2

From: Evolution of energy metabolism and its compartmentation in Kinetoplastida

Figure 2

The energy metabolism of bloodstream-form (a) and procyclic T. brucei (b). Enzymes: 1, hexokinase; 2, glucose-6-phosphate isomerase; 3, phosphofructokinase; 4, aldolase; 5, triosephosphate isomerase; 6, glyceraldehyde-3-phosphate dehydrogenase; 7, phosphoglycerate kinase; 8, glycerol-3-phosphate dehydrogenase; 9, glycerol kinase; 10, phosphoglycerate mutase; 11, enolase; 12, pyruvate kinase; 13, glycerol-3-phosphate oxidase; 14, phosphoenolpyruvate carboxykinase; 15, L-malate dehydrogenase; 16, fumarase; 17, fumarate reductase; 18, pyruvate phosphate dikinase; 19, pyruvate dehydrogenase complex; 20, acetate:succinate CoA transferase; 21, proline oxidase; 22, Δ'-pyrroline-5-carboxylate reductase; 23, glutamate semialdehyde dehydrogenase; 24, glutamate dehydrogenase; 25, α-ketoglutarate dehydrogenase; 26, succinyl CoA synthetase; 27, FAD-dependent glycerol-3-phosphate dehydrogenase. Abbreviations: AA, amino acid; AcCoA, acetyl-CoA; 1,3-BPGA, 1,3-bisphosphoglycerate; c, cytochrome c; Citr, citrate; DHAP, dihydroxyacetone phosphate; Fum, fumarate; G-3-P, glyceraldehyde 3-phosphate; Glu, glutamate; Gly-3-P, glycerol 3-phosphate; KG, α-ketoglutarate; Mal, malate; OA, 2-oxoacid; Oxac, oxaloacetate; PEP, phosphoenolpyruvate; 3-PGA, 3-phosphoglycerate; Succ, succinate; Succ-CoA, succinyl-CoA; UQ, ubiquinone. Substrates and secreted end-products are indicated in green and red, respectively, and boxed. Enzymes involved in reactions represented by dashed lines are present, but experiments indicated that no significant fluxes occurred through these steps [62, 95]. A complex II is depicted because succinate dehydrogenase activity and succinate-dependent repiration have been demonstrated in mitochondria of T. brucei procyclics and T. cruzi epimastigotes [167, 168]. However the role of succinate respiration in the overall metabolism of these cells remains to be clarified. No evidence has been reported that electron transfer through complex I of the respiratory chain of trypanosomatids is coupled to proton expulsion. The mitochondrion contains two membranes; the inner membrane containing the respiratory chain and H+-ATPase has been drawn in this figure.

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