scholarly journals Partition kinetics of ribulose-1,5-bisphosphate carboxylase from Rhodospirillum rubrum.

1985 ◽  
Vol 260 (2) ◽  
pp. 944-948
Author(s):  
A Jaworowski ◽  
I A Rose
Keyword(s):  
Rhodospirillum Rubrum ◽  
Bisphosphate Carboxylase ◽  
Kinetics Of

scholarly journals A kinetic study of ribulose bisphosphate carboxylase from the photosynthetic bacterium Rhodospirillum rubrum

1978 ◽  
Vol 173 (2) ◽  
pp. 467-473 ◽  
Author(s):  
J T Christeller ◽  
W A Laing
Keyword(s):  
Rhodospirillum Rubrum ◽  
Photosynthetic Bacterium ◽  
Active Enzyme ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Higher Plant ◽  
Activation Kinetics ◽  
Bisphosphate Carboxylase ◽  
Proposed Model ◽  
Kinetics Of

The activation kinetics of purified Rhodospirillum rubrum ribulose bisphosphate carboxylase were analysed. The equilibrium constant for activation by CO(2) was 600 micron and that for activation by Mg2+ was 90 micron, and the second-order activation constant for the reaction of CO(2) with inactive enzyme (k+1) was 0.25×10(-3)min-1 . micron-1. The latter value was considerably lower than the k+1 for higher-plant enzyme (7×10(-3)-10×10(-3)min-1 . micron-1). 6-Phosphogluconate had little effect on the active enzyme, and increased the extent of activation of inactive enzyme. Ribulose bisphosphate also increased the extent of activation and did not inhibit the rate of activation. This effect might have been mediated through a reaction product, 2-phosphoglycolic acid, which also stimulated the extent of activation of the enzyme. The active enzyme had a Km (CO2) of 300 micron-CO2, a Km (ribulose bisphosphate) of 11–18 micron-ribulose bisphosphate and a Vmax. of up to 3 mumol/min per mg of protein. These data are discussed in relation to the proposed model for activation and catalysis of ribulose bisphosphate carboxylase.

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.

Models of integrated photosynthesis of cells and leaves

1989 ◽  
Vol 323 (1216) ◽  
pp. 357-367 ◽  
Keyword(s):  
Simplified Model ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Optimal Arrangement ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Kinetics Of

The kinetics of ribulose bisphosphate carboxylase-oxygenase (Rubisco) are integrated with the stoichiometry of NADPH consumption and production in a simplified model of C 3 chloroplast photosynthesis. The extension to a leaf is discussed with reference to the gradient of irradiance that is always present within the leaf. The optimal arrangement of photosyntheic capacity is discussed in this context. Attention is then given to the effects of gradients of CO 2 concentration that sometimes occur when stomata close in a heterogeneous fashion.

Limitation of the Rate of Ribulosebisphosphate Carboxylase Activation by Carbamylation and Ribulosebisphosphate Carboxylase Activase Activity: Development and Tests of a Mechanistic Model

1996 ◽  
Vol 23 (2) ◽  
pp. 141 ◽  
Author(s):  
IE Woodrow ◽  
ME Kelly ◽  
KA Mott
Keyword(s):  
Mechanistic Model ◽  
Large Subunit ◽  
Intercellular Co2 Concentration ◽  
Rubisco Activase ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Bisphosphate Carboxylase ◽  
Ribulosebisphosphate Carboxylase ◽  
Kinetics Of ◽  
Rubisco Activation

A mechanistically-based model of light-mediated activation of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is developed. The model describes the kinetics of Rubisco activation following a relatively rapid increase in photon flux density (PPFD) from an initially low level. Underlying the model is the assumption that there are two slow processes that could potentially limit the rate of light-mediated Rubisco activation. These processes are the addition of the activator CO2 to the large subunit of Rubisco, which is accompanied by a conformational change in the enzyme (carbamylation), and activase-mediated removal of ribulose 1,5-bisphosphate from the inactive form of the enzyme. The contribution of these slow processes to the overall activation kinetics of Rubisco was resolved by measuring Rubisco activation in whole spinach leaves using non-steady-state CO2 exchange. It was found that when the change in PPFD was relatively small and a correspondingly small proportion of the Rubisco pool was activated, the kinetics of activation were highly sensitive to the intercellular CO2 concentration (ci). The apparent rate constant for activation under these conditions was found to be similar to that for the carbamylation of purified spinach Rubisco. When the change in PPFD and the proportion of Rubisco activated was relatively large, however, the kinetics of Rubisco activation were almost completely CO2 insensitive and were consistent with those of an enzyme-catalysed reaction. It is suggested that (1) CO2-insensitive activation reflects the operation of Rubisco activase and (2) the increasing CO2 sensitivity seen as the change in PPFD decreases reflects a transition to limitation by carbamylation.

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