Figure 4.
A, Effect of VC/VO of Rubisco on leaf cellular growth and CO2 uptake while absorbing equal amounts of photon. B, Flux map of the central metabolism in photorespiring leaves under normal conditions (VC/VO = 3). C, Variation in fluxes through key enzymes upon varying levels of VC/VO. The color intensity of the lines in the central carbon metabolic network (B) corresponds to the flux values obtained from simulations. C was drawn by normalizing the flux values with respect to VC/VO = 3. DCW, Dry cell weight. Metabolite abbreviations not defined in the text are as follows: 1,3-PGA, 1,3-diphosphoglycerate; 2-PGA, 2-phosphoglycerate; Ac-CoA, acetyl-CoA; ADP-G, ADP-Glc; E-4-P, d-erythrose-4-phosphate; F-1,6-bP, Fru-1,6-bisP; F-6-P, Fru-6-P; G-1-P, Glc-1-P; G3P, glyceraldehyde-3-phosphate; G-6-P, Glc-6-P; HP, hydroxypyruvate; PEP, phosphoenolpyruvate; PRPP, phosphoribosyl pyrophosphate; Q, ubiquinone; QH2, ubiquinol; S-6-P, Suc-6-P; R-5-P, Rib-5-P; Ru-1,5-bP, ribulose-1,5-bisphosphate; Ru-5-P, ribulose-5-phosphate; S-1,7-bP, sedoheptulose-1,7-bisphosphate; S-7-P, sedoheptulose-7-phosphate; Xu-5-P, xylulose-5-phosphate; UDP-G, UDP-Glc. Enzyme abbreviations not defined in the text are as follows: ACO, aconitase; ALAAT, Ala aminotransferase; ALD, aldolase; APS, Glc-1-P adenylyltransferase; ASP1, Asp aminotransferase; COX, cytochrome c oxidase; CSY, citrate synthase; FBP, Fru-bisphosphatase; FK, fructokinase; FUM, fumarase; GABA-TK, γ-aminobutyrate aminotransferase; GAD, Glu decarboxylase; GAPDH, glyceraldehyde phosphate dehydrogenase; GDC, Gly decarboxylase; GGAT, Gly aminotransferase; GLYK, glycerate kinase; GLN1, Glu ammonia ligase; GOX, glycolate oxidase; GS, Glu synthase (ferredoxin dependent); HPR, hydroxypyruvate reductase; MDH, malate dehydrogenase; NAD9, NADH dehydrogenase; PEPE, phosphoenolpyruvate enolase; PFK, phosphofructokinase; PGI, Glc-6-P isomerase; PGK, phosphoglycerate kinase; PGLYCM, phosphoglycerate mutase; PGM, phosphoglucomutase; PGP, phosphoglycolate phosphatase; PPC, phosphoenolpyruvate carboxylase; PPDK, pyruvate orthophosphate dikinase; PPS, pyruvate-water dikinase; PRK, phosphoribulokinase; PSLR, photosynthetic light reaction; PYK, pyruvate kinase; RBCS-C, ribulose-1,5-bisphosphate carboxylase; RBCS-O, ribulose-1,5-bisphosphate oxygenase; RPE, Rib-5-phosphate epimerase; SBP, sedoheptulose-bisphosphatase; SBPGL, sedoheptulose 1,7-bisphosphate d-glyceraldehyde-3-phosphate lyase; SDH, succinate dehydrogenase; SGAT, Ser glyoxylate aminotransferase; SHM, Ser hydroxymethyltransferase; SPP, Suc phosphatase; SPS, Suc phosphate synthase; SSADH, succinic semialdehyde dehydrogenase; SSI, starch synthase; TKT, transketolase; TPI, triose phosphate isomerase; UGPP, UDP-Glc pyrophosphorylase. [See online article for color version of this figure.]