Structural Properties and Ribulosebisphosphate Carboxylase and Oxygenase Activity of Fraction-1 Protein from the Marine Alga Halimeda cylindracea (Chlorophyta)

1976 ◽  
Vol 3 (1) ◽  
pp. 93 ◽  
Author(s):  
T Akazawa ◽  
CB Osmond
Keyword(s):  
Large Subunit ◽  
Homogeneous State ◽  
Plant Type ◽  
Precipitation Line ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Subunit A ◽  
Fraction 1 Protein ◽  
Oxygenase Activity ◽  
Ribulosebisphosphate Carboxylase

Ribulosebisphosphate carboxylase/oxygenase activity was detected in Halimeda cylindracea and Chaetomorpha crassa. In H. cylindracea carboxylase activity (72-250 micromoles CO2 fixed per hour per milligram chlorophyll) was sufficient to account for measured photosynthetic rates. The activity of the oxygenase was only 1 % that of the carboxylase but otherwise both enzymes showed properties similar to those of the same enzymes in higher green plants. Fraction-1 protein from H. cylindracea was purified to a homogeneous state as tested by poly- acrylamide gel electrophoresis at pH 8.9. The activity of the ribulose-1,5-bisphosphate carboxylase in the purified preparations was 0.1 micromoles CO2 fixed per minute per milligram protein (pH 7.0). The H. cylindracea fraction-1 protein was shown to comprise two subunits, A and B, with molecular weights 5.4 × 104, and 1.35 x 104, respectively, typical of the plant-type ribulose-1,5-bisphosphate carboxylase. The amino acid composition of the large subunit A was similar to that from spinach and Chlorella enzymes, whereas that of the subunit B was markedly distinguishable from the enzymes of other origins. The close resemblance of the H. cylindricea protein to the plant enzymes was further supported by the formation of a spur in the double immunodiffusion precipitation line, indicating probable existence of sequence-homology of the catalytic larger subunit A, typical of the plant-type enzyme molecules.

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.

Inhibitory Action of Glufosinate on Photosynthesis

1993 ◽  
Vol 48 (3-4) ◽  
pp. 369-373 ◽  
Author(s):  
Aloysius Wild ◽  
Christine Wendler
Keyword(s):  
Enzyme Activity ◽  
Calvin Cycle ◽  
Atmospheric Conditions ◽  
Direct Inhibition ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Transamination Reaction ◽  
Ribulosebisphosphate Carboxylase ◽  
High Concentrations ◽  
Respiratory Conditions

Glufosinate (phosphinothricin) irreversibly blocks the glutamine synthetase which subsequently gives rise to an accumulation of ammonium and to a strong decrease in some amino acids, especially glutamine and glutamate.Under atmospheric conditions (400 ppm CO2, 21% O2) glufosinate causes a rapid inhibition of photosynthesis, too. H ow ever, under non-photo respiratory conditions (1000 ppm CO2, 2% O2) only a slight inhibition of photosynthesis occurs with glufosinate. Since under both conditions an accumulation of ammonium occurs, it is concluded that inhibition of photosynthesis is not induced by the higher concentrations of ammonium. The results rather suggest that the absence of amino donors in the glycolate pathway leads to a break-down of the transamination reaction of glyoxylate to glycine. This causes an inhibition of photorespiration and as a further consequence the inhibition of photosynthesis. There are two hypotheses for explaining this phenomenon. One of them supposes that the blockade in the glycolate pathway produces a lack of Calvin cycle intermediates which subsequently is the cause of the inhibition of photo synthesis. The other one suggests a direct inhibition of the ribulose-1,5-bisphosphate carboxylase by the accumulation of glyoxylate and P-glycolate.After treatment with different intermediates of the Calvin cycle and photorespiration to gether with glufosinate no decrease in the inhibition of photosynthesis could be measured. This suggests that the inhibition of photosynthesis is not induced by a depletion of intermediates of the Calvin cycle.Tests on the effect of glyoxylate and P-glycolate on ribulosebisphosphate carboxylase activity showed that in crude leaves extracts the enzyme activity can only be inhibited by high concentrations of these substances. However, in intact spinach chloroplasts the enzyme activity can be blocked by using much lower concentrations of glyoxylate. This may indicate that the ribulosebisphosphate carboxylase activase is affected by this metabolite and that this may be the reason for an inhibition of photosynthesis after treatment with glufosinate.

Assimilate Source-Sink Relationships in Capsicum annuum L. II. Effects of Fruiting and Defloration on the Photosynthetic Capacity and Senescence of the Leaves

1977 ◽  
Vol 4 (5) ◽  
pp. 771 ◽  
Author(s):  
AJ Hall ◽  
CJ Brady
Keyword(s):  
Protein Synthesis ◽  
Protein Content ◽  
Photosynthetic Capacity ◽  
Co2 Exchange ◽  
Carboxylase Activity ◽  
Intracellular Resistance ◽  
Fraction 1 Protein ◽  
Age Related ◽  
Ribulosebisphosphate Carboxylase ◽  
Source Sink

The photosynthetic capacity of leaves of fruiting Capsicum plants that expanded during or shortly after anthesis remained steady throughout the growth of the fruit. The formation and growth of the fruit was associated with a reversal of the decline in photosynthetic capacity of some of the leaves that had expanded before anthesis. In deflorated plants, the photosynthetic capacity of leaves at all levels of insertion declined continuously. The variations with age of the net CO2 exchange of the leaf inserted one internode above the fruit were attributable almost exclusively to changes in intracellular resistance, while in the corresponding leaf of deflorated plants both leaf and intracellular transfer resistances were important determinants of photosynthesis. Fruiting reduced the age-related loss of soluble and fraction 1 protein and of ribulosebisphosphate carboxylase activity in the leaf immediately above the fruit. The ratio of fraction 1 protein synthesis to that of other soluble proteins in fully expanded leaves showed no tendency to decline with age in plants of either type. Intracellular resistance in fruiting plants did not appear to be linked to changes in either fraction 1 protein content or ribulosebisphosphate carboxylase activity.

Changes in the heterogeneity of ribulosebisphosphate carboxylase–oxygenase in winter rye induced by cold hardening

1982 ◽  
Vol 60 (9) ◽  
pp. 897-903 ◽  
Author(s):  
N. P. A. Huner ◽  
D. B. Hayden
Keyword(s):  
Large Subunit ◽  
Cold Hardening ◽  
Winter Rye ◽  
Charge Heterogeneity ◽  
Two Dimensional Gel Electrophoresis ◽  
Bisphosphate Carboxylase ◽  
Ribulose 1 ◽  
Ribulosebisphosphate Carboxylase ◽  
Quaternary Structures ◽  
Molecular Weight Heterogeneity

The quaternary structures of ribulose-1, 5-bisphosphate carboxylase–oxygenase from cold-hardened and unhardened Puma rye were examined by two-dimensional gel electrophoresis according to the method of O'Farrell. The results indicate that major changes in charge heterogeneity occur in the large subunit of this enzyme during growth at cold-hardening temperatures. The extent of charge heterogeneity decreased upon adaptation of Puma rye to cold-hardening temperatures. In addition to charge heterogeneity, molecular weight heterogeneity was also evident in the large subunit polypeptides of the enzyme from cold-hardened and unhardened Puma rye.

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