Rs at the active site of Rubisco and thus prevents the

Rs at the active site of Rubisco and thus prevents the loss of its catalytic activity. The cascade of side-reactions performed by Rubisco is yet to be fully understood although recent achievements in mathematical modelling of Rubisco reactions offer the theoretical background for predicting `side-effects’ by simulating the NT-157 web overall kinetic behaviour [9]. Another corollary of low kcat and of the large size of the holoenzyme (560 kDa) is that Rubisco comprises up to 50 of soluble protein in photosynthetic tissues and is probably the most abundant enzyme on Earth [10]. In terrestrial plants with C4 photosynthesis or crassulacean acid metabolism (CAM), and in many aquatic organisms, photorespiration is partially or completely suppressed by the operation of an auxiliary CO2-concentrating mechanism. C4 plants initially fix atmospheric carbon in the mesophyll cells using phosphoenolpyr-Rubisco Evolution in C4 Eudicotsuvate carboxylase, an enzyme with a high effective affinity for CO2 (HCO32 being the true substrate of the enzyme). Further four-carbon compounds (malate or aspartate) produced by this fixation are transported to the specialized bundle-sheath cells, where CO2 is released and fixed by Rubisco. Rubisco from C4 plants, which experiences ,10-fold higher CO2 concentrations in bundle-sheath cells than does the enzyme in C3 plants [11], has a lower affinity for CO2 but a higher kcat (<4 s21). Having less specific but faster Rubisco and no photorespiration losses, C4 plants require 60 to 75 less Rubisco to match the photosynthetic capacity of C3 plants [12,13]. In fact, many C4 plants such as maize, sugarcane and sorghum are among the most productive of all species cultivated agriculturally. Although C4 plants appeared relatively recently in evolutionary terms and constitute only 3 of terrestrial plant species, they are already among the most successful and abundant groups in warm climates and are responsible for about 20 of terrestrial gross primary productivity [14,15]. C4 photosynthesis evolved independently in at least 62 recognizable lineages of angiosperms and represents one of the most striking examples of a convergent biochemical adaptation in plants [16]. However, since its discovery, most attention has been devoted to the more numerous and agriculturally important C4 monocots in the Poaceae, while C4 eudicots have been studied less intensively. The family Amaranthaceae sensu lato (i.e. including Chenopodiaceae) [17,18] contains about 180 genera and 2500 species, of which approximately 750 are C4 species [16], making it by far the largest C4 family among eudicots and the third-largest among angiosperms (after Poaceae and Cyperaceae). C4 photosynthesis evolved at least 15 times within Amaranthaceae [16] making this family a good model to study coevolution of C4 photosynthesis and Rubisco. Notably, the Amaranthaceae exceed the Poaceae and Cyperaceae in the diversity of photosynthetic organ anatomy [19], and 12926553 is the only angiosperm family containing terrestrial C4 plants that lack Kranz anatomy, with three species having a single-cell rather than the more usual dual-cell C4 system [20,21]. The predominantly buy A196 tropical Amaranthaceae sensu stricto and primarily temperate and subtropical Chenopodiaceae have long been treated as two closely related families (see review in [19]) until the formal proposal that Chenopodiaceae should be included within the expanded Amaranthaceae based on a lack of separation between the two families in sequ.Rs at the active site of Rubisco and thus prevents the loss of its catalytic activity. The cascade of side-reactions performed by Rubisco is yet to be fully understood although recent achievements in mathematical modelling of Rubisco reactions offer the theoretical background for predicting `side-effects’ by simulating the overall kinetic behaviour [9]. Another corollary of low kcat and of the large size of the holoenzyme (560 kDa) is that Rubisco comprises up to 50 of soluble protein in photosynthetic tissues and is probably the most abundant enzyme on Earth [10]. In terrestrial plants with C4 photosynthesis or crassulacean acid metabolism (CAM), and in many aquatic organisms, photorespiration is partially or completely suppressed by the operation of an auxiliary CO2-concentrating mechanism. C4 plants initially fix atmospheric carbon in the mesophyll cells using phosphoenolpyr-Rubisco Evolution in C4 Eudicotsuvate carboxylase, an enzyme with a high effective affinity for CO2 (HCO32 being the true substrate of the enzyme). Further four-carbon compounds (malate or aspartate) produced by this fixation are transported to the specialized bundle-sheath cells, where CO2 is released and fixed by Rubisco. Rubisco from C4 plants, which experiences ,10-fold higher CO2 concentrations in bundle-sheath cells than does the enzyme in C3 plants [11], has a lower affinity for CO2 but a higher kcat (<4 s21). Having less specific but faster Rubisco and no photorespiration losses, C4 plants require 60 to 75 less Rubisco to match the photosynthetic capacity of C3 plants [12,13]. In fact, many C4 plants such as maize, sugarcane and sorghum are among the most productive of all species cultivated agriculturally. Although C4 plants appeared relatively recently in evolutionary terms and constitute only 3 of terrestrial plant species, they are already among the most successful and abundant groups in warm climates and are responsible for about 20 of terrestrial gross primary productivity [14,15]. C4 photosynthesis evolved independently in at least 62 recognizable lineages of angiosperms and represents one of the most striking examples of a convergent biochemical adaptation in plants [16]. However, since its discovery, most attention has been devoted to the more numerous and agriculturally important C4 monocots in the Poaceae, while C4 eudicots have been studied less intensively. The family Amaranthaceae sensu lato (i.e. including Chenopodiaceae) [17,18] contains about 180 genera and 2500 species, of which approximately 750 are C4 species [16], making it by far the largest C4 family among eudicots and the third-largest among angiosperms (after Poaceae and Cyperaceae). C4 photosynthesis evolved at least 15 times within Amaranthaceae [16] making this family a good model to study coevolution of C4 photosynthesis and Rubisco. Notably, the Amaranthaceae exceed the Poaceae and Cyperaceae in the diversity of photosynthetic organ anatomy [19], and 12926553 is the only angiosperm family containing terrestrial C4 plants that lack Kranz anatomy, with three species having a single-cell rather than the more usual dual-cell C4 system [20,21]. The predominantly tropical Amaranthaceae sensu stricto and primarily temperate and subtropical Chenopodiaceae have long been treated as two closely related families (see review in [19]) until the formal proposal that Chenopodiaceae should be included within the expanded Amaranthaceae based on a lack of separation between the two families in sequ.