Fig. 3

The Calvin cycle and photorespiration pathway. The CNBP candidates are depicted in red font. Additional photorespiratory enzymes that were pulled down during the affinity purification procedure but excluded during the stringent elimination process (Table S2) are shown in blue font, where SAGT is ALANINE: GLYOXYLATE AMINOTRANSFERASE and CAT2 is CATALASE 2. The Calvin cycle and photorespiration pathway are connected by the dual-functioning enzyme RUBISCO shown in green. The CNBP candidate CA1 interconverts soluble HCO³⁻ to gaseous CO₂ and controls the supply of CO₂ to RUBISCO and regulates stomatal closure through HCO³⁻ effects on anion channels thereby further affecting the supply of CO₂ to the plant. The CNBP candidates PGK1, GAPB and TKL are enzymes in the Calvin cycle. PGK1 and GAPB convert Ribulose-1, 5-bisphosphate (RuBP) into the triose phosphate, D-glyceraldehyde-3-phosphate which can feed into sucrose and starch biosynthesis. TKL is involved in the regeneration of RuBP and significantly controls carbon flux through the Calvin cycle. The CNBP candidates GOX1 and SHMT1 are enzymes in the photorespiration pathway. GOX1 catalyses the conversion of glycolate to glyoxylate with the concomitant release of H₂O₂ as a by-product. SHMT1 converts two molecules of glycine to serine, CO₂, NH₃ and NADH. This CO₂ can feedback into the Calvin cycle while NH₃ can feed into nitrogen assimilation