Variation in photosynthetic electron transport capacity in vivo and its effects on the light modulation of ribulose bisphosphate carboxylase

1986 ◽  
Vol 8 (3) ◽  
pp. 249-256 ◽  
Author(s):  
Scott E. Taylor ◽  
Norman Terry
Keyword(s):  
Electron Transport ◽  
Photosynthetic Electron Transport ◽  
Ribulose Bisphosphate Carboxylase ◽  
Light Modulation ◽  
Transport Capacity ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase

Ribulose bisphosphate carboxylase—oxygenase: its role in photosynthesis

1986 ◽  
Vol 313 (1162) ◽  
pp. 305-324 ◽  
Keyword(s):  
Electron Transport ◽  
Carbon Assimilation ◽  
Kinetic Properties ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Rubp Carboxylase ◽  
Bisphosphate Carboxylase ◽  
Triose Phosphate ◽  
Ribulose Bisphosphate Carboxylase Oxygenase

Synthesis of triose phosphate by the chloroplast requires three substrates: light, CO 2 and orthophosphate (P i ). In the response of the rate of carbon assimilation to the concentration of CO 2 , the kinetic properties of RuBP carboxylase-oxygenase (Rubisco) constitute the main limitation at low CO 2 concentrations, while at higher concentrations of CO 2 the limitation is shifted towards the reactions leading to the regeneration of the substrate, RuBP, driven by electron transport. In these circumstances, light or P i or both, can become limiting. The characteristics of Rubisco that can affect photosynthesis fall under three main headings: (1) amount and kinetic constants; (2) activation state; and (3) regulation of catalysis (including the role of effectors, such as Pt and glycerate 3-phosphate (PGA)). These characteristics are analysed, and the role of changes in activity of the enzyme is discussed in the context of limitation and regulation of the photosynthetic process. Other factors considered are the regeneration of RuBP and its relation to electron transport, P i supply, and photorespiration. The influence that expected increases in atmospheric CO 2 concentration, and/or genetic improvements in the characteristics of the enzyme, may have on the present balance between the partial processes of photosynthesis, is discussed.

scholarly journals Comparison of the kinetic properties of ribulose bisphosphate carboxylase in chloroplast extracts of spinach, sunflower and four other reductive pentose phosphate-pathway species

1978 ◽  
Vol 171 (2) ◽  
pp. 477-482 ◽  
Author(s):  
M E Delaney ◽  
D A Walker
Keyword(s):  
Electron Transport ◽  
Pentose Phosphate Pathway ◽  
Pentose Phosphate ◽  
The Other ◽  
Kinetic Properties ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase

Extracts from chloroplasts of spinach, sunflower and four other reductive pentose phosphate (C3)-pathway species were measured spectrophotometrically with or without a modified preactivation procedure. In all six species this modification yielded Km (CO2) values in the range of 7-15 micron and maximum velocities, at 20 degrees C, of 129-431 mumol of CO2 carboxylated/h per mg of chlorophyll. In general, both the carboxylation and electron-transport capacities of sunflower were somewhat greater than that of the other species, and this is discussed in relation to the superior rates of photosynthesis believed to be displayed by the parent tissue.

Immunolocalization of Rubisco Activase and Rubisco in C3 and C4 Plant Tissues

2000 ◽  
Vol 6 (S2) ◽  
pp. 472-473
Author(s):  
S. Madhavan ◽  
M. S. Miller-Goodman ◽  
K. W. Lee
Keyword(s):  
Higher Plants ◽  
Tight Binding ◽  
Rubisco Activase ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Microscopic Studies ◽  
Sugar Phosphates

Ribulose bisphosphate carboxylase/oxygenase (Rubisco), an abundant enzyme in chloroplasts, must be activated by CO2 in order for it to catalyze the carboxylation of ribulose bisphosphate. Rubisco activase, a nuclear encoded chloroplast protein was first identified as a biochemical lesion in the rca mutant of Arabidopsis (1) which lacked this enzyme. Study of Rubisco in this mutant (2) and transgenic tobacco plants with reduced Rubisco activase levels showed that Rubisco could not achieve and maintain an adequate level of activity, in vivo, without an activase. Rubisco activase promotes ‘activation’ of Rubisco by overcoming the deleterious effects of tight binding sugar phosphates and low chloroplast CO2 levels on catalysis and carbamylation (1).Rubisco activase has been detected in higher plants (3), in unicellular green algae (4,5) and in cyanobacteria (6). Though the presence of Rubisco in guard cell chlroplasts was a subject of controversy, several immunolight and immunoelectron microscopic studies have demonstrated the presence of Rubisco in guard cells (7).

scholarly journals Studies on the assembly of large subunits of ribulose bisphosphate carboxylase in isolated pea chloroplasts.

1982 ◽  
Vol 94 (1) ◽  
pp. 20-27 ◽  
Author(s):  
H Roy ◽  
M Bloom ◽  
P Milos ◽  
M Monroe
Keyword(s):  
Large Subunit ◽  
Ribulose Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate ◽  
Dissociation Reaction ◽  
Bisphosphate Carboxylase ◽  
In Organello ◽  
Intact Chloroplasts ◽  
Isolated Chloroplasts

Ribulose bisphosphate carboxylase consists of cytoplasmically synthesized "small" subunits and chloroplast-synthesized "large" subunits. Large subunits of ribulose bisphosphate carboxylase synthesized in vivo or in organello can be recovered from intact chloroplasts in the form of two different complexes with sedimentation coefficients of 7S and 29S. About one-third to one-half of the large subunits synthesized in isolated chloroplasts are found in the 7S complex, the remainder being found in the 29S complex. Upon prolonged illumination of the chloroplasts, newly synthesized large subunits accumulate in the 18S ribulose bisphosphate carboxylase molecule and disappear from both the 7S and the 29S large subunit complexes. The 29S complex undergoes an in vitro dissociation reaction and is not as stable as ribulose bisphosphate carboxylase. The data indicate that (a) the 7S large subunit complex is a chloroplast product, the (b) the 29S large subunit complex is labeled in vivo, that (c) each of these two complexes can account quantitatively for all the large subunits assembled into RuBPCase in organello, and that (d) excess large subunits are degraded in chloroplasts.

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