Effect of Different CO2 Regimes on the Induction of Crassulacean Acid Metabolism in Mesembryanthemum crystallinum L

1979 ◽  
Vol 6 (6) ◽  
pp. 589 ◽  
Author(s):  
K Winter
Keyword(s):  
Water Stress ◽  
Phosphoenolpyruvate Carboxylase ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
High Salinity ◽  
Stomatal Closure ◽  
Initial Step ◽  
Mesembryanthemum Crystallinum ◽  
Initial Event ◽  
Response To Water

Induction of crassulacean acid metabolism (CAM) in Mesembryanthemum crystallinum in response to high salinity was studied in plants grown in different CO2 regimes to determine whether the induction of CAM could be controlled by CO2 supply in the light and dark; a possible consequence of stomatal closure in response to water stress. The activity of extractable phosphoenolpyruvate carboxylase (EC 4.1.1.31) and the nocturnal change in malate content were followed at frequent intervals after onset of the treatments. The results suggest that the initial event during the induction of CAM is a change in the biochemical apparatus, indicated by the activity of phosphoenolpyruvate carboxylase, which then leads to the day/night fluctuations of malate synthesis typical of CAM. This initial step is not controlled by the availability of CO2 in the light or dark.

scholarly journals Phosphoenolpyruvate carboxylase from pennywort (Umbilicus rupestris). Changes in properties after exposure to water stress

1984 ◽  
Vol 218 (2) ◽  
pp. 387-393 ◽  
Author(s):  
P P Daniel ◽  
J A Bryant ◽  
F I Woodward
Keyword(s):  
Water Stress ◽  
Phosphoenolpyruvate Carboxylase ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Marked Decrease ◽  
Cam Plants ◽  
Allosteric Inhibitor ◽  
Allosteric Effector ◽  
Incomplete Form ◽  
C3 Photosynthesis

Umbilicus rupestris (pennywort) switches from C3 photosynthesis to an incomplete form of crassulacean acid metabolism (referred to as ‘CAM-idling’) when exposed to water stress (drought). This switch is accompanied by an increase in the activity of phosphoenolpyruvate carboxylase. This enzyme also shows several changes in properties, including a marked decrease in sensitivity to acid pH, a lower Km for phosphoenolpyruvate, very much decreased sensitivity to the allosteric inhibitor malate, and increased responsiveness to the allosteric effector glucose 6-phosphate. The Mr of the enzyme remains unchanged, at approx. 185 000. These changes in properties of phosphoenolpyruvate carboxylase are discussed in relation to the roles of the enzyme in C3 and in CAM plants.

scholarly journals Induction of Crassulacean Acid Metabolism in Mesembryanthemum crystallinum by High Salinity: Mass Increase and de Novo Synthesis of PEP-Carboxylase

1987 ◽  
Vol 83 (4) ◽  
pp. 915-919 ◽  
Author(s):  
Roswitha Höfner ◽  
Luz Vazquez-Moreno ◽  
Klaus Winter ◽  
Hans J. Bohnert ◽  
Jürgen M. Schmitt
Keyword(s):  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
High Salinity ◽  
De Novo ◽  
Mesembryanthemum Crystallinum ◽  
De Novo Synthesis ◽  
Pep Carboxylase ◽  
Mass Increase

Change in Properties of Phosphoenolpyruvate Carboxylase From the Crassulacean Acid Metabolism Plant Mesembryanthemum crystallinum After Isolation

1981 ◽  
Vol 8 (1) ◽  
pp. 115 ◽  
Author(s):  
K Winter
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Molecular Basis ◽  
Enzyme Catalysis ◽  
Crassulacean Acid Metabolism ◽  
Acid Metabolism ◽  
Dark Period ◽  
Mesembryanthemum Crystallinum ◽  
Cytoplasmic Ph ◽  
Strong Inhibitor ◽  
Crassulacean Acid Metabolism Plant

Phosphoenolpyruvate carboxylase (EC 4.1.1.31) in desalted extracts from the inducible crassulacean acid metabolism plant M. crystallinum exists in a highly malate-sensitive state when isolated from plants in the light, and after isolation rapidly changes into a less sensitive state typical of the dark period. Loss of sensitivity to malate inhibition after isolation is largely prevented when the enzyme is extracted and stored at acid pH and in the presence of malate. This demonstrates that, in addition to its effect as a strong inhibitor of enzyme catalysis during the light, malate may also maintain the highly malate-sensitive state of phosphoenolpyruvate carboxylase during the light, particularly in combination with a lowered cytoplasmic pH. These experiments also establish conditions necessary for the study of the molecular basis for the change in properties of phosphoenolpyruvate carboxylase.

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