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.

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.

Binding of 3-phosphoglycerate leads to both activation and stabilisation of ADP-glucose pyrophosphorylase from apple leaves

2005 ◽  
Vol 32 (9) ◽  
pp. 839
Author(s):  
Rui Zhou ◽  
Lailiang Cheng
Keyword(s):  
Heat Treatment ◽  
Thermal Stability ◽  
Enzyme Activity ◽  
Inorganic Phosphate ◽  
Thermal Inactivation ◽  
Specific Activity ◽  
Apple Leaves ◽  
Apparent Homogeneity ◽  
Adp Glucose Pyrophosphorylase ◽  
High Concentrations

Apple leaf ADP-glucose pyrophosphorylase was purified 1436-fold to apparent homogeneity with a specific activity of 58.9 units mg–1. The enzyme was activated by 3-phosphoglycerate (PGA) and inhibited by inorganic phosphate (Pi) in the ADPG synthesis direction. In the pyrophosphorolytic direction, however, high concentrations of PGA (> 2.5 mm) inhibited the enzyme activity. The enzyme was resistant to thermal inactivation with a T0.5 (temperature at which 50% of the enzyme activity is lost after 5 min incubation) of 52°C. Incubation with 2 mm PGA or 2 mm Pi increased T0.5 to 68°C. Incubation with 2 mm dithiothreitol (DTT) decreased T0.5 to 42°C, whereas inclusion of 2 mm PGA in the DTT incubation maintained T0.5 at 52°C. DTT-induced decrease in thermal stability was accompanied by monomerisation of the small subunits. Presence of PGA in the DTT incubation did not alter the monomerisation of the small subunits of the enzyme induced by DTT. These findings indicate that binding of PGA renders apple leaf AGPase with a conformation that is not only more efficient in catalysis but also more stable to heat treatment. The physiological significance of the protective effect of PGA on thermal inactivation of AGPase is discussed.

scholarly journals Design and in vitro realization of carbon-conserving photorespiration

2018 ◽  
Vol 115 (49) ◽  
pp. E11455-E11464 ◽  
Author(s):  
Devin L. Trudeau ◽  
Christian Edlich-Muth ◽  
Jan Zarzycki ◽  
Marieke Scheffen ◽  
Moshe Goldsmith ◽  
...  
Keyword(s):  
Carbon Fixation ◽  
Calvin Cycle ◽  
Computational Design ◽  
Carbon Loss ◽  
Fixation Rate ◽  
Bisphosphate Carboxylase ◽  
Stoichiometric Model ◽  
Synthetic Routes ◽  
Coa Reductase

Photorespiration recycles ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) oxygenation product, 2-phosphoglycolate, back into the Calvin Cycle. Natural photorespiration, however, limits agricultural productivity by dissipating energy and releasing CO2. Several photorespiration bypasses have been previously suggested but were limited to existing enzymes and pathways that release CO2. Here, we harness the power of enzyme and metabolic engineering to establish synthetic routes that bypass photorespiration without CO2 release. By defining specific reaction rules, we systematically identified promising routes that assimilate 2-phosphoglycolate into the Calvin Cycle without carbon loss. We further developed a kinetic–stoichiometric model that indicates that the identified synthetic shunts could potentially enhance carbon fixation rate across the physiological range of irradiation and CO2, even if most of their enzymes operate at a tenth of Rubisco’s maximal carboxylation activity. Glycolate reduction to glycolaldehyde is essential for several of the synthetic shunts but is not known to occur naturally. We, therefore, used computational design and directed evolution to establish this activity in two sequential reactions. An acetyl-CoA synthetase was engineered for higher stability and glycolyl-CoA synthesis. A propionyl-CoA reductase was engineered for higher selectivity for glycolyl-CoA and for use of NADPH over NAD+, thereby favoring reduction over oxidation. The engineered glycolate reduction module was then combined with downstream condensation and assimilation of glycolaldehyde to ribulose 1,5-bisphosphate, thus providing proof of principle for a carbon-conserving photorespiration pathway.

Role of salicylic acid in regulation of cadmium toxicity in wheat ( Triticum aestivum L.)

2009 ◽  
Vol 57 (3) ◽  
pp. 321-333 ◽  
Author(s):  
H. Moussa ◽  
S. EL-Gamal
Keyword(s):  
Pyruvate Carboxylase ◽  
Cadmium Toxicity ◽  
Triticum Aestivum L ◽  
Carboxylase Activity ◽  
Bisphosphate Carboxylase ◽  
Cd Accumulation ◽  
Phosphoenol Pyruvate ◽  
Relative Water ◽  
Aba Content

Treatment with CdCl 2 (0, 100, 400 and 1000 μM) resulted in the inhibition of root dry biomass and root elongation and to increased Cd accumulation in the roots. These treatments also decreased the relative water content, chlorophyll content, 14 CO fixation, phosphoenol pyruvate carboxylase and ribulose-1,5-bisphosphate carboxylase activity and abscisic acid (ABA) content, while increasing the malondialdehyde, hydrogen peroxide and free proline contents and causing changes in the chloroplast and root ultrastructure. Pretreatment of seeds with SA (500 μM) for 20 h resulted in the amelioration of these 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 CO2 Assimilation, Photosynthetic Enzymes, and Carbohydrates of `Concord' Grape Leaves in Response to Iron Supply

2004 ◽  
Vol 129 (5) ◽  
pp. 738-744 ◽  
Author(s):  
Li-Song Chen ◽  
Brandon R. Smith ◽  
Lailiang Cheng
Keyword(s):  
Sucrose Concentration ◽  
Calvin Cycle ◽  
Sucrose Phosphate Synthase ◽  
Nonstructural Carbohydrates ◽  
Bisphosphate Carboxylase ◽  
Chl A ◽  
Photosynthetic Enzymes ◽  
Fe Content ◽  
Significant Difference ◽  
Assimilation Capacity

Own-rooted 1-year-old `Concord' grapevines (Vitis labruscana Bailey) were fertigated twice weekly for 11 weeks with 1, 10, 20, 50, or 100 μm iron (Fe) from ferric ethylenediamine di (o-hydroxyphenylacetic) acid (Fe-EDDHA) in a complete nutrient solution. As Fe supply increased, leaf total Fe content did not show a significant change, whereas active Fe (extracted by 2,2′-dipyridyl) content increased curvilinearly. Chlorophyll (Chl) content increased as Fe supply increased, with a greater response at the lower Fe rates. Chl a: b ratio remained relatively constant over the range of Fe supply, except for a slight increase at the lowest Fe treatment. Both CO2 assimilation and stomatal conductance increased curvilinearly with increasing leaf active Fe, whereas intercellular CO2 concentrations decreased linearly. Activities of key enzymes in the Calvin cycle, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoribulokinase (PRK), stromal fructose-1,6-bisphosphatase (FBPase), and a key enzyme in sucrose synthesis, cytosolic FBPase, all increased linearly with increasing leaf active Fe. No significant difference was found in the activities of ADP-glucose pyrophosphorylase (AGPase) and sucrose phosphate synthase (SPS) of leaves between the lowest and the highest Fe treatments, whereas slightly lower activities of AGPase and SPS were observed in the other three Fe treatments. Content of 3-phosphoglycerate (PGA) increased curvilinearly with increasing leaf active Fe, whereas glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), and the ratio of G6P: F6P remained unchanged over the range of Fe supply. Concentrations of glucose, fructose, sucrose, starch, and total nonstructural carbohydrates (TNC) at both dusk and predawn increased with increasing leaf active Fe. Concentrations of starch and TNC at any given leaf active Fe content were higher at dusk than at predawn, but both glucose and fructose showed the opposite trend. No difference in sucrose concentration was found at dusk or predawn. The export of carbon from starch breakdown during the night, calculated as the difference between dusk and predawn measurements, increased as leaf active Fe content increased. The ratio of starch to sucrose at both dusk and predawn also increased with increasing leaf active Fe. In conclusion, Fe limitation reduces the activities of Rubisco and other photosynthetic enzymes, and hence CO2 assimilation capacity. Fe-deficient grapevines have lower concentrations of nonstructural carbohydrates in source leaves and, therefore, are source limited.

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