Figure 1.

The carboxylation and oxygenation reactions of Rubisco. (a) Diagram of Rubisco-catalyzed reactions in C3 plants. Carboxylation of RuBP initiates the Calvin Cycle and leads to production of carbohydrates. Oxygenation of RuBP initiates photorespiration and results in the net loss of fixed CO₂ and NH₃, and consumption of energy. The carboxylation of RuBP by Rubisco and subsequent reactions in the Calvin Cycle are shown in green arrows. The oxygenation of RuBP by Rubisco and the subsequent photorespiration process are shown in red arrows. RuBP = Ribulose-1,5-bisphosphate; 3PGA = 3-phosphoglycerate; 2PG = 2-phosphoglycolate; G3P = glyceraldehyde 3-phosphate. (b) Rubisco specificity (S_C/O) and maximum carboxylation rate (V_C) in tobacco (C3 model species), wheat (C3 crop), limonium (L. gibertii, C3 with high specificity), maize and sorghum (C4 crops), S. elongatus (cyanobacteria, β-carboxysome species) and Rhodospirilum rubrum (purple bacteria, α-carboxysome species). Data are averages of values reported by: (Jordan and Ogren 1981, Jordan and Ogren 1983, Jordan and Ogren 1984, Makino et al. 1985, Parry et al. 1987, Parry et al. 1989, Sage and Seemann 1993, Kane et al. 1994, Delgado, et al. 1995, Uemura et al. 1996, Whitney et al. 1999, Whitney et al. 2001, Pearce 2006, Mueller-Cajar et al. 2007, Parry et al. 2007, Kubien et al. 2008, Mueller-Cajar and Whitney 2008, Sharwood et al. 2008, Carmo-Silva et al. 2010, Genkov et al. 2010, Whitney et al. 2011b, Occhialini et al. 2016, Prins et al. 2016).