Ribulose-l,5-diphosphate

Cyclo(Pro-Tyr), also known as maculosin, is a phytotoxin produced by the fungus Altemaria alternata, and has been found to cause black necrotic lesions on the leaves of spotted knapweed. The mechanism underlying the phytotoxic action of cyclo(Pro-Tyr) may lie in its ability to inhibit ribulose-l,5-diphosphate carboxylase. ... 

The Calvin-Benson photos mthetic cycle is dominant in hardwoods and conifers. The primary CO2 fixation or carboxylation reaction involves the enz mie ribulose-l,5-diphosphate carboxylase and the first stable product is a 3-carbon compound (100). 

Fig. 4. Radioautogram of products of 60 seconds photosynthesis with C 0-. Radioautograph of two-dimensional paper chromatogram of products formed by Chlorella pyrenoidosa during 60 seconds of photosynthesis with C 0 . Abbreviations P, POaH" UDPG, uridine diphosphoglucose PGA, 3-phosphoglyceric acid PEPA, phosphoenolpyruvic acid. Sugar diphosphate includes ribulose-l,5-diphosphate, sedoheptulose-1,7-diphosphate, and fructose-1,6-diphosphate.

Three of the reactions in the Calvin cycle are irreversible and serve to drive the whole cycle in a clockwise direction. The first step in the cycle can be regarded as the action of carbon dioxide on ribulose-l,5-diphosphate to produce two molecules of 3-phosphoglyceric acid which is then converted into 1,3-diphosphoglyceric acid by the action of ATP and the appropriate enzyme. The important first step is catalysed by the phosphoprotein D-ribulose-1,5 bis phosphate carboxylase oxygenase (RUBISCO) which is probably the most abundant enzyme in the world. 

The whole photosynthetic process requires 12 molecules of ATP and 12 molecules of NADPH to convert six molecules of CO2 into one molecule of glucose. Another six molecules of ATP are required for re-cycling the ribulose-l,5-diphosphate. The net reaction of the Calvin cycle is... 

The difference between this route and the Calvin cycle lies in the fact that the CO2 is fixed, not into ribulose-l,5-diphosphate, but into phosphoenol pyruvate with the intermediary formation of C4 dicarboxylic acids. Hence the name, the Q dicarboxylic acid pathway. One of the C4 dicarboxylic acids transmits the CO2 further with the formation, ultimately, of 3-phosphoglyceric acid. 

D-Ribulose-l,5-diphosphate carboxylase (Dasycladus davaeformis) 0.730 77P2... 

Ogren, W.L., and Bowes, G. 1972. Oxygen inhibition and other properties of soybean ribulose 1,5-diphosphate carboxylase. 7. Biol. Chem. 247 2171-2176. 

DSC, reported that SCN, another chaotropic anion, stabilizes BSA in the same conditions. It is known that SCN binds strongly to BSA [191]. We observed [195] that Ca2+ and Mg2+ decrease QD and Tm of ribulose 1,5-diphosphate carboxylase (Rubisco) to a limited extent but in a definite and steady way as their concentration increases over the ionic strength range 0-0.3 mol/L Na+ and NH+4 had an opposite effect. In the case of Rubisco, specificity of the effect of Ca2+ and Mg2 + is supported by the fact that these cations are known to bind to the protein and to affect its enzymatic activity by inducing structural changes. Specific effects of Na+ and Ca2+ are also observed by DSC on the heat stability of a-lactalbumin [190] they result in a linear increase of QD with the cation/protein molar ratio up to 1, followed by a plateau (Fig. 7). 

After a time, several other sugar phosphates were identified. Most important among these were the seven-carbon compounds, sedoheptulose-7-phosphate (IX) and sedoheptulose-l,7-diphosphate (SDP) (X), and the five-carbon compounds, ribulose-l,5-diphos-phate (RuDP) (II) and ribose-5-phosphate (XI), xylulose-5-phosphate (XII), and ribulose-5-phosphate (I) (Benson, et al., 1952). The roles of these compounds in the path of carbon in photosynthesis became more clear after they had been degraded to locate the position of radiocarbon atoms within the individual molecules (Bassham et al., 1954). 

Scheme 11.1. A cartoon representation of the addition of carbon dioxide (CO2) to the five-carbon ketosugar diphosphate, ribulose-l,5-bisphosphate, in an imagined aldol-type process in the presence of (which might further be imagined to coordinate with the enediol as in pinacol formation, Chapter 8) and the enzyme ribulose-l,5-bisphosphate carboxylase (EC 4.1.1.39). Since 2-carboxy-3-ketoribitol-l,5-bisphosphate is not isolable, the sense of addition re or si) cannot be established. Retroaldol-type fragmentation is presumed to occur to yield, after suitable proton tautomeric adjustments, 2 equivalents of 3-phosphoglycerate (Cl + C5 = 2 C3).

Buchanan, B. B. and SchOrmann, P. (1973) Ribulose 1,5-diphosphate carboxylase a regulatory enzyme in the photosynthetic assimilation of carbon dioxide. In Current Topics in Cellular Regulation (Horecker, B. L. and Stadtman, E. R., eds.), pp. 1-20. Academic Press, New York. 

Malic acid is a very active intermediary product of grape metabolism. The vine contains the L-(—) malic isomer. The vine assimilates carbon dioxide in the air by a C3 mechanism (Ruflher et al., 1983). In this manner, during the dark phase of photosynthesis, the leaves and young green grapes fix CO2 on ribulose 1,5-diphosphate to produce phospho-glyceric acid, which condenses to form hexoses and may also become dehydrated into phosphoenol pyruvic acid. CO2, catalyzed by PEP carboxylase, is fixed on this acid to form oxaloacetic acid, which is, in turn, reduced into malic acid. 

LIST OF ABBREVIATIONS ACP, acyl carrier protein 5ALA, 5-aminolevulinic acid AU, 6-azauracyl CAP, chloramphenicol CHI, cycloheximide DCIP, 2,6-dichlorophenolindo-phenol DCMU, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea DG, digalactosyl-diglyceride DPC, diphenylcarbazide ETS, electron-transport system FDPase, alkaline fructose 1,6-diphosphate phosphatase G-3-P, glyceraldehyde-3-phosphate MG, monogalactosyldiglycer-ide PSI, PSII, photosystems I and II P700, active center of photosystem I PMS, phenazine methosulfate Q, photosystem II quencher Ru-l,5-diP, ribulose-1,5-diphosphate SDS, sodium dodecylsulfate SL, sulfolipid. 

Multi-Enzyme Cofactor Requiring Processes - A more complex level of applied enzymology is reached in the use of multi-enzyme schemes to synthesize complex molecules. Examples of such syntheses include ribu-lose-1,5-diphosphate, important in the study of ribulose-diphosphate carboxylase lactosamine,from the first use of the Lelolr pathway enzjnnes in synthesis and S-adenosyl-L-methionine. ... 

Scheme 12.24. Chorismate is converted to anthranilate (and glutamate [Gin, E] and pyruvate) using anthranilate synthase (EC 4.1.3.27). Anthranilate and ribose-1,5-diphosphate, in the presence of anthranilate phosphoribosyltransferase (EC 2.4.2.18), produces N- 5-phospho-P-D-ribosyl) anthranilate. Finally, indole-3-glycerolphosphate is formed via l-(2-carboxyphenyl-amino)-l-deoxy-D-ribulose-5-phosphate with loss of carbon dioxide (CO2).

Abbreviations used Gal-l-P, galactose-l-phosphate UDPG, uridine diphosphate glucose G-l-P, glucose-l-phosphate G-6-P, glucose-6-phosphate F-6-P, fructose-6-phosphate F-l,6-P, fructose-1,6-diphosphate G-3-P, glyceraldehyde-3-phosphate DHAP, dihydroxyacetone phosphate F-l-P, fructose-1-phosphate PG, 6-phospho-gluconic acid R-5-P, ribulose-5-phosphate S-7-P, sedoheptulose-7-phosphate. 

Rabbit muscle aldolase (RAMA) furnished ketose l ho hates with 3(S)/4(i ) stereochemistry from dihydioxyacetone phosphate (DHAP) and simple aldehydes. When a-hydroxyaldehydes were used kinetic resolution occurred, provided there was a negative charge (e.g. CCX) ) 4 or 5 atoms away from the aldehyde group. Fructose 1,6-diphosphate aldolase from spinach leaves catalysed similar condensations between DHAP and aldehydes with a substrate specifity somewhat different from that of RAMA. A reinvestigation of the stmc course of the hexulose phosphate synthetase-catalysed condensation between ribulose S-phosphate and simple aldehydes is covered in Chapter 2. 

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