Rubisco ribulose-1,5-bisphosphate

Figure 4.8 The active site in all a/p barrels is in a pocket formed by the loop regions that connect the carboxy ends of the p strands with the adjacent a helices, as shown schematically in (a), where only two such loops are shown, (b) A view from the top of the barrel of the active site of the enzyme RuBisCo (ribulose bisphosphate carboxylase), which is involved in CO2 fixation in plants. A substrate analog (red) binds across the barrel with the two phosphate groups, PI and P2, on opposite sides of the pocket. A number of charged side chains (blue) from different loops as welt as a Mg ion (yellow) form the substrate-binding site and provide catalytic groups. The structure of this 500 kD enzyme was determined to 2.4 A resolution in the laboratory of Carl Branden, in Uppsala, Sweden. (Adapted from an original drawing provided by Bo Furugren.)...

The virtual SWISS-PROT entries have a far-reaching effect on TrEMBL. For example, the virtual entry for the Rubisco (ribulose-bisphosphate carboxylase) large chain affects 3300 TrEMBL entries. Therefore a system has been developed to decompose these virtual entries into rules that are stored in a relational database with proper version control features. 

Rubisco (ribulose bisphosphate carboxylase-oxygenase) The enzyme that accomplishes carbon fixation in photosynthesis by adding CO2 to ribulose-1,5-bisphosphate. It can also add O2 in place of CO2, initiating photorespiration. 

Rubisco (Ribulose Bisphosphate Carboxylase-Oxygenase) The enzyme that accomplishes carbon... 

In this reaction, one molecule of ribulose-1,5-bisphosphate (metabolite 1) and one molecule of CO2 (metabolite 2) give rise to two molecules of 3-phosphoglycerate (metabolite 3). The enzyme responsible has the EC number 4.1.1.39. The annotated enzyme list shows that this refers to ribulose bisphosphate carboxylase ( rubisco for short). Rubisco belongs to enzyme class 4 (the lyases) and, within that group, to subclass 4.1 (the car-boxy-lyases). It contains copper as a cofactor ([Cu]). 

Why is ribulose bisphosphate carboxylase (RUBISCO) a poor target for a herbicide ... 

The enzyme responsible for the fixation of CO2, ribulose bisphosphate carboxylase/oxygenase (RUBISCO), also catalyses the oxygenation of ribulose bisphosphate to form one molecule of phosphoglycerate and one molecule of phosphoglycolate. Under normal C02 and 02 concentrations six ribulose bisphosphate molecules react with oxygen for every 15 that react with carbon dioxide. 

Ribothymidylic acid residue 813 Ribozyme(s) 649 - 652, 239 artificial 652 hairpin 649,651s hammerhead 649, 651 leadzyme, 651s Ribulose 164s Ribulose bisphosphate 707s Ribulose bisphosphate carboxylase (Rubisco)... 

The key reaction of the Calvin-Benson cycle of C02 reduction is the carboxylation of ribulose bisphos-phate to form two molecules of 3-phosphoglycerate (Eq. 13-48). The properties of ribulose bisphosphate carboxylase (rubisco, Figs. 13-10 to 13-12), which catalyzes this reaction, are discussed in Chapter 13. It... 

The following substances are either inhibitors or activators of rubisco, the enzyme that catalyzes the condensation of C02 with ribulose bisphosphate to yield 3-phosphoglycerate. State whether the substance should be an activator or an inhibitor... 

The dark reactions (carbon-fixation reactions) use the ATP and NADPH produced by the light reactions to fix carbon dioxide as carbohydrate sucrose and starch. The reactions form a cycle (the Calvin cycle) in which the enzyme ribulose bisphosphate carboxylase (rubisco), located in the stroma, condenses a C02 molecule with ribulose 1,5-bisphosphate to produce two molecules of 3-phosphoglycerate. Other reactions then regenerate the ribulose... 

This pathway is sometimes called the Calvin-Benson cycle, after the biochemists who elucidated it. The 5-carbon, doubly phosphorylated carbohydrate, ribulose bisphosphate is the acceptor for CO2 the enzyme is called ribulose-bisphosphate carboxylase/oxygenase (called Rubisco). 

This set of reactions is very detrimental to the efficiency of photosynthesis. Oxygen is added to carbon, CO2 is lost, energy is consumed, and ribulose bisphosphate is destroyed. For a plant to be able to increase the discrimination of Rubisco for CO2 would obviously be advantageous, but that hasn t happened, either naturally or through the efforts of scientists. An increased concentration of CO2 in the atmosphere may lead to increased photosynthesis and decreased photorespiration, but high CO2 concentrations would also contribute to global warming (and the increased photosynthetic carbon fixation would not likely reduce the amount of CO2 in any event). 

Figure 8-13. Schematic illustration of Rubisco (ribulose-l,5-bisphosphate carboxylase/oxygenase) acting as the branch point for photosynthesis and photorespiration. All three of the organelles involved, but only a few of the biochemical steps, are indicated. ( represents phosphate. Note that 3-phosphoglycerate and glycolate refer to the dissociated forms of 3-phosphoglyceric acid and glycolic acid, respectively.)...

The first stable product of carbon fixation by the enzyme, ribulose bisphosphate carboxylase (Rubisco), is glyceraldehyde 3-phosphate, a 3-C sugar. This 3-C sugar is fed into biosynthetic pathways and forms the basis for all organic compounds produced by photosynthetic organisms. Fixed carbon and major and trace elements... 

Figure 9 A model of the cyanobacterial carbon concentrating mechanism from Synechococcus PCC 7942, a freshwater species. Solid circles represent transporters located on the plasma membrane and interior to the cell wall. Boxes represent the catalyzing enzymes CA, Carbonic Anhydrase RUBISCO, Ribulose 1-5 bisphosphate Carboxylase Oxygenase. The carboxysome is the site of carbon fixation (dark reactions) and the thylakoid is the site of the light reactions of photosynthesis (after Badger et aL, 2002).

Figure 10 A hypothetical model of carbon acquisition in the marine diatom Thalassiosira weissflogii. Solid circles represent transporters. Catalyzing enzymes CA, carbonic anhydrase PEPC, phosphoenol pyruvate carboxylase PEPCK phospoenol pyruvate carboxykinase RUBISCO, Ribulose 1-5 bisphosphate Carboxylase Oxygenase (after...

The reaction is catalyzed by ribulose bisphosphate carboxylase, "Rubisco", which is probably the most abundant enzyme on earth (it is 10-25% of leaf protein). 

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