scholarly journals Drought Stress and Elevated CO2 Effects on Soybean Ribulose Bisphosphate Carboxylase Activity and Canopy Photosynthetic Rates

1987 ◽  
Vol 83 (3) ◽  
pp. 573-578 ◽  
Author(s):  
J. Cu V. Vu ◽  
Leon H. Allen ◽  
George Bowes
Keyword(s):  
Drought Stress ◽  
Elevated Co2 ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Photosynthetic Rates ◽  
Co2 Effects

scholarly journals Ribulose 1,5-bisphosphate carboxylase. Effect on the catalytic properties of changing methionine-330 to leucine in the Rhodospirillum rubrum enzyme

1986 ◽  
Vol 235 (3) ◽  
pp. 839-846 ◽  
Author(s):  
B E Terzaghi ◽  
W A Laing ◽  
J T Christeller ◽  
G B Petersen ◽  
D F Hill
Keyword(s):  
Rhodospirillum Rubrum ◽  
Oligonucleotide Primer ◽  
Similar Amount ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
In The Wild ◽  
The Stability

Oligonucleotide-directed mutagenesis of cloned Rhodospirillum rubrum ribulose bisphosphate carboxylase/oxygenase with a synthetic 13mer oligonucleotide primer was used to effect a change at Met-330 to Leu-330. The resultant enzyme was kinetically examined in some detail and the following changes were found. The Km(CO2) increased from 0.16 to 2.35 mM, the Km(ribulose bisphosphate) increased from 0.05 to 1.40 mM for the carboxylase reaction and by a similar amount for the oxygenase reaction. The Ki(O2) increased from 0.17 to 6.00 mM, but the ratio of carboxylase activity to oxygenase activity was scarcely affected by the change in amino acid. The binding of the transition state analogue 2-carboxyribitol 1,5-bisphosphate was reversible in the mutant and essentially irreversible in the wild type enzyme. Inhibition by fructose bisphosphate, competitive with ribulose bisphosphate, was slightly increased in the mutant enzyme. These data suggest that the change of the residue from methionine to leucine decreases the stability of the enediol reaction intermediate.

scholarly journals Ribulose bisphosphate carboxylase/oxygenase in toluene-permeabilized Rhodospirillum rubrum

1983 ◽  
Vol 212 (1) ◽  
pp. 45-54 ◽  
Author(s):  
I Storrø ◽  
B A McFadden
Keyword(s):  
Rhodospirillum Rubrum ◽  
Decay Rates ◽  
Dual Function ◽  
Co2 Removal ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
The Stability

Toluene-permeabilized Rhodospirillum rubrum cells were used to study activation of and catalysis by the dual-function enzyme ribulose bisphosphate carboxylase/oxygenase. Incubation with CO2 provided as HCO3-, followed by rapid removal of CO2 at 2 degrees C and subsequent incubation at 30 degrees C before assay, enabled a determination of decay rates of the carboxylase and the oxygenase. Half-times at 30 degrees C with 20 mM-Mg2+ were 10.8 and 3.7 min respectively. Additionally, the concentrations of CO2 required for half-maximal activation were 56 and 72 microM for the oxygenase and the carboxylase respectively. After activation and CO2 removal, inactivation of ribulose bisphosphate oxygenase in the presence of 1 mM- or 20mM-Mn2+ was slower than that with the same concentrations of Co2+ or Mg2+. Only the addition of Mg2+ supported ribulose bisphosphate carboxylase activity, as Mn2+, Co2+ and Ni2+ had no effect. A pH increase after activation in the range 6.8-8.0 decreased the stability of the carboxylase but in the range 7.2-8.0 increased the stability of the oxygenase. With regard to catalysis. Km values for ribulose 1,5-bisphosphate4- were 1.5 and 67 microM for the oxygenase and the carboxylase respectively, and 125 microM for O2. Over a broad range of CO2 concentrations in the activation mixture, the pH optima were 7.8 and 8-9.2 for the carboxylase and the oxygenase respectively. The ratio of specific activities was constant (9:1 for the carboxylase/oxygenase) of ribulose bisphosphate carboxylase/oxygenase in toluene-treated Rsp. rubrum. Below concentrations of 10 microM-CO2 in the activation mixture, this ratio increased.

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