Phosphoenolpyruvate Carboxykinase in C4 Plants: Its Role and Regulation

1997 ◽  
Vol 24 (4) ◽  
pp. 459 ◽  
Author(s):  
Robert P. Walker ◽  
Richard M. Acheson ◽  
László I. Técsi ◽  
Richard C. Leegood
Keyword(s):  
Molecular Mass ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Plants ◽  
Panicum Maximum ◽  
C4 Plant ◽  
Cam Plants ◽  
Crude Extracts ◽  
High Concentrations ◽  
Regulatory Properties

Some of the recent findings which revise our view of the role and regulation of phosphoenolpyruvate carboxykinase (PEPCK) in C4 plants are discussed. Evidence is presented that PEPCK is present at appreciable activities in the bundle-sheath of some NADP-malic enzyme-type C4 plants, such as maize, but it was not detectable in NAD-malic enzyme-type C4 plants. PEPCK is rapidly inactivated in crude extracts of leaves of the C4 plant, Panicum maximum. This inactivation could be prevented by high concentrations of dithiothreitol or by the inclusion of ADP or ATP, suggesting the involvement of thiols at the active site. PEPCK is also subject to rapid proteolysis in crude extracts of a range of C4 plants, resulting in cleavage to a smaller (62 kDa) form. This can be reduced by extraction at high pH and by the inclusion of SDS, but it means that intact PEPCK has never been purified from a C4 plant. The molecular mass of PEPCK varies considerably in C4 plants, unlike C3 and CAM plants in which it is usually 74 kDa. PEPCK is phosphorylated during darkness (and reversed by light) in some C4 plants with PEPCK of a larger molecular mass, such as Panicum maximum (71 kDa), but it was not phosphorylated in the PEPCK-type C4 plant, Sporobolus pyramidalis (69 kDa). The known regulatory properties of PEPCK are discussed in relation to its role in C4 photosynthesis, in particular its sensitivity to regulation by adenylates and by Mn2+.

Photosynthesis in Phosphoenolpyruvate Carboxykinase-Type C4 Species: Properties of Nad-Malic Enzyme From Urochloa panicoides

1987 ◽  
Vol 14 (5) ◽  
pp. 517 ◽  
Author(s):  
JN Burnell
Keyword(s):  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Bundle Sheath ◽  
Photosynthetic Pathway ◽  
C4 Plant ◽  
C4 Species ◽  
Absolute Requirement ◽  
Pep Carboxykinase ◽  
Fructose 1,6 Bisphosphate ◽  
Regulatory Properties

NAD-malic enzyme (EC 1.1.1.39) was purified from bundle sheath strands of Urochloa panicoides (a phosphoenolpyruvate carboxykinase-type C4 plant) and its kinetic and regulatory properties were investigated. The native enzyme has a molecular weight of about 470 000 and is an octomer composed of two slightly different monomers which occur in a 1 : 1 ratio. The enzyme has an absolute requirement for Mn2+, is stimulated by CoA, acetyl CoA, fructose 1,6-bisphosphate and SO42- and is inhibited by HCO3, oxaloacetate, 2-oxoglutarate and pyruvate. The enzyme is shown to be localised in the mito- chondria. The purified NAD-malic enzyme is unable to catalyse the carboxylation of pyruvate according to the reverse reaction. These findings are discussed in relation to the C4 photosynthetic pathway and its possible role in PEP carboxykinase-type C4 plants.

Purification and Properties of Phosphoenolpyruvate Carboxykinase from C4 Plants

1986 ◽  
Vol 13 (5) ◽  
pp. 577 ◽  
Author(s):  
JN Burnell
Keyword(s):  
Molecular Weight ◽  
Phosphoenolpyruvate Carboxykinase ◽  
C4 Plants ◽  
Kinetic Properties ◽  
Panicum Maximum ◽  
Ph Optimum ◽  
Wide Ph Range ◽  
Pep Carboxykinase ◽  
Nucleotide Specificity ◽  
Fructose 1,6 Bisphosphate

Phosphoenolpyruvate (PEP) carboxykinase (EC 4.1.1.49) from the leaves of Urochloa panicoides, Chloris gayana and Panicum maximum has been purified to homogeneity and its properties determined. The enzyme from all three PEP carboxykinase-type C4 plants have similar physical and kinetic properties. The native enzyme has a molecular weight of 380 000 and its monomeric molecular weight is about 64 000, suggesting the enzyme is hexameric. It is active over a wide pH range and has a pH optimum between 7.4 and 8.2, has a wide nucleotide specificity, has an absolute requirement for Mn2+ and is stimulated by C-. The enzyme is inhibited by 3-phosphoglyceric acid, fructose 6-phosphate and fructose 1,6-bisphosphate; the mechanism of inhibition is discussed. The purified PEP carboxykinase is unable to catalyse the conversion of oxaloacetate to pyruvate, nor does it possess pyruvate kinase activity. These findings are discussed in relation to the C4 photosynthetic pathway operating in PEP carboxykinase-type C4 plants.

Regulatory Properties of Pyruvate Kinase from Liver of the Summer-Active Arctic Ground Squirrel

1974 ◽  
Vol 52 (6) ◽  
pp. 547-559 ◽  
Author(s):  
Hans W. Behrisch ◽  
Craig E. Johnson
Keyword(s):  
Pyruvate Kinase ◽  
Ground Squirrel ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Effect Of Temperature ◽  
Arctic Ground Squirrel ◽  
Physiological Importance ◽  
Atp Inhibition ◽  
High Concentrations ◽  
Regulatory Properties ◽  
Regulation Of Enzyme Activity

The properties of liver pyruvate kinase (PyK) from summer-active Arctic ground squirrel (Citellus undulatus) were examined over the physiological temperature range of the animal. One form of the enzyme with a pI (isoelectric point) value of 5.3 was observed and exhibited kinetics similar to those of L-type PyK. This form has a molecular weight of 243 000, similar to that of M-type PyK. Enzyme–phosphoenolpyruvate (PEP) affinity falls with decreasing temperature while affinity for ADP increases under these conditions. The effect of temperature upon extent of negative cooperativity of PEP binding and its possible physiological importance are briefly discussed. Fructose-1,6-phosphate (FDP) increases the affinity of PyK for PEP but has no effect upon enzyme-ADP interaction. However, Vmax in the presence of saturating concentrations of both substrates is increased two to threefold by FDP, the allosteric activator. Ground squirrel PyK is inhibited by ATP. Inhibition by ATP of PyK activity is diminished by decreasing the temperature or by increasing the concentrations of substrate. FDP reverses this inhibition but the degree of reversal is sensitive to substrate concentration and temperature. Inhibition by ATP is competitive for the PEP site and appears to be of the "mixed-competitive" variety when carried out at varying concentrations of ADP. Inhibition by alanine is noncompetitive for both substrate sites. As a result of the very high concentrations of amino acids needed to obtain appreciable inhibition of live PyK, this does not appear to be a physiological means of regulation of enzyme activity. The effect of intermediates of the glycolytic, pentose shunt, and Krebs acid cycle pathways upon PyK activity is briefly discussed. Inosine nucleotides, involved in the reversal of the PyK reaction by phosphoenolpyruvate carboxykinase, have a strong modulating effect upon PyK activity. These data suggest formal mechanisms for the regulation of liver PyK in the ground squirrel.

scholarly journals Phosphorylation of phosphoenolpyruvate carboxykinase in plants. Studies in plants with C4 photosynthesis and Crassulacean acid metabolism and in germinating seeds

1996 ◽  
Vol 317 (3) ◽  
pp. 653-658 ◽  
Author(s):  
Robert P. WALKER ◽  
Richard C. LEEGOOD
Keyword(s):  
Molecular Mass ◽  
Crassulacean Acid Metabolism ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Acid Metabolism ◽  
C4 Photosynthesis ◽  
C4 Grasses ◽  
Cam Plants ◽  
Sds Page ◽  
Germinating Seeds

We have previously shown that phosphoenolpyruvate carboxykinase (PEPCK) is phosphorylated in vivo in the cotyledons of darkened cucumber seedlings and that phosphorylation is reversed by light [Walker and Leegood (1995) FEBS Lett. 362, 70–74]. In this study the molecular mass of PEPCK was estimated in a range of gluconeogenic seedlings and in leaves of C4 plants and plants with Crassulacean acid metabolism (CAM). Phosphorylation of PEPCK was studied in these plants by feeding tissues with [32P]Pi and assessing phosphorylation by SDS/PAGE and autoradiography of either total proteins or of immunoprecipitated protein. In gluconeogenic seedlings and most CAM plants PEPCK had a molecular mass of 74 kDa, whereas in C4 grasses the molecular mass of PEPCK was always smaller and varied from 67–71 kDa. In all gluconeogenic seedlings and leaves of CAM plants PEPCK was phosphorylated, but it was not phosphorylated in all species of C4 grasses studied. In CAM plants, phosphorylation of PEPCK occurred at night and dephosphorylation occurred during the day. In C4 grasses phosphorylation occurred when leaves were darkened and the enzyme was dephosphorylated following illumination, but it was only phosphorylated in those plants with larger (71 kDa) molecular mass forms of PEPCK.

scholarly journals NAD+-malic enzyme. Regulatory properties of the enzyme from Ascaris suum.

1976 ◽  
Vol 251 (12) ◽  
pp. 3599-3602
Author(s):  
W J Landsperger ◽  
B G Harris
Keyword(s):  
Malic Enzyme ◽  
Ascaris Suum ◽  
Regulatory Properties

Possible involvement of phosphoenolpyruvate carboxylase and NAD-malic enzyme in response to drought stress. A case study: a succulent nature of the C4-NAD-ME type desert plant, Salsola lanata (Chenopodiaceae)

2017 ◽  
Vol 44 (12) ◽  
pp. 1219
Author(s):  
Zhibin Wen ◽  
Mingli Zhang
Keyword(s):  
Enzyme Activity ◽  
Drought Stress ◽  
Phosphoenolpyruvate Carboxylase ◽  
Malic Enzyme ◽  
C4 Plants ◽  
Leaf Water Content ◽  
Transcriptional Level ◽  
Desert Plant ◽  
Severe Stress ◽  
Real Time Quantitative Pcr

The co-ordination between the primary carboxylating enzyme phosphoenolpyruvate carboxylase (PEPC) and the further decarboxylating enzymes is crucial to the efficiency of the CO2-concentrating mechanism in C4 plants, and investigations on more types of C4 plants are needed to fully understand their adaptation mechanisms. In this study we investigated the effect of drought on carboxylating enzyme PEPC, and the further decarboxylating NAD-malic enzyme (NAD-ME) of Salsola lanata Pall. (Chenopodiaceae) – an annual succulent C4-NAD-ME subtype desert plant. We investigated enzyme activity at the transcriptional level with real-time quantitative PCR and at the translational level by immunochemical methods, and compared S. lanata with other forms of studied C4 plants under drought stress. Results showed that only severe stress limited PEPC enzyme activity (at pH 8.0) of S. lanata significantly. Considering that PEPC enzyme activity (at pH 8.0) was not significantly affected by phosphorylation, the decrease of PEPC enzyme activity (at pH 8.0) of S. lanata under severe stress may be related with decreased PEPC mRNA. The suggestion of increased phosphorylation of the PEPC enzyme in plants under moderate stress was supported by the ratio of PEPC enzyme activity at pH 7.3/8.0, as PEPC enzyme is inhibited by L-malate and the evidence of the 50% inhibiting concentration of L-malate. NAD-ME activity decreased significantly under moderate and severe stress, and coincided with a change of leaf water content rather than the amount of α-NAD-ME mRNA and protein. Leaf dehydration may cause the decrease of NAD-ME activity under water stress. Compared with other C4 plants, the activities of PEPC and NAD-ME of S. lanata under drought stress showed distinct features.

scholarly journals Determination Contents of Total Phenolic Pigments and Spectrophotometric Characterization of Crude Extracts of Ten Tinctorial Plants of Niger which is Usable in Solar Energy

2018 ◽  
Vol 14 (33) ◽  
pp. 389
Author(s):  
Souley Kallo Moutari ◽  
Ayouba Mahamane Abdoulkadri ◽  
Abdourahamane Saidou Boulhassane ◽  
Adamou Rabani ◽  
Ikhiri Khalid
Keyword(s):  
Solar Energy ◽  
Raw Materials ◽  
Dye Sensitized Solar Cells ◽  
Electrical Energy ◽  
Total Phenolic ◽  
Environmental Friendliness ◽  
Pigment Synthesis ◽  
Chlorophyll Pigments ◽  
Crude Extracts ◽  
High Concentrations

Dye Sensitized-Solar Cells (DSSCs) have been extensively investigated because of their environmental friendliness and low production cost. At the heart of these is the photosensitive pigment that plays a key role in the collection of sunlight radiations and its conversion into electrical energy. However, the toxicity and the cost of pigment synthesis limit the increased use of these prototypes. Natural pigments can be an effective, sustainable, and inexpensive alternative. This paper focuses on determining the main phenolic pigments contents and evaluating the solar light collection capacity of ten (10) tinctorial plants crude extracts, via UV-Visible Spectrophotometry. High concentrations of total polyphenols (46.54 mgEqAG/g), flavonoids (10.95 mgEqQuer/g), anthocyanins (181.9 mgL-1 ), and tannins (40.1 mgL-1 ) were recorded in some extracts of these plants. Absorption spectra showed intense absorption domains around 280 nm in the ultraviolet (UV), and also in the visible (400 to 700 nm). These absorptions would be attributed to the π-π* and n-π* electron transitions of the chromophores present in the anthocyanin, flavonoid, carotenoid, and chlorophyll pigments of these plants. The high contents of pigments and the appropriate spectrophotochemical properties make the extracts of these tinctorial plants to become potential raw materials that are useful in solar energy technology.

Quantum Yields of Photosystem II Electron Transport and Carbon Dioxide Fixation in C4 Plants

1990 ◽  
Vol 17 (5) ◽  
pp. 579 ◽  
Author(s):  
JP Krall ◽  
GE Edwards
Keyword(s):  
Carbon Dioxide ◽  
Electron Transport ◽  
Quantum Yield ◽  
Photosystem Ii ◽  
Malic Enzyme ◽  
Co2 Fixation ◽  
C4 Plants ◽  
Quantum Yields ◽  
Ps Ii ◽  
Co2 Concentrations

The quantum yields of non-cyclic electron transport from photosystem II (determined from chlorophyll a fluorescence) and carbon dioxide assimilation were measured in vivo in representative species of the three subgroups of C4 plants (NADP-malic enzyme, NAD-malic enzyme and PEP-carboxykinase) over a series of intercellular CO2 concentrations (CI) at both 21% and 2% O2. The CO2 assimilation rate was independent of O2 concentration over the entire range of Ci (up to 500 μbar) in all three C4 subgroups. The quantum yield of PS II electron transport was similar, or only slightly greater, in 21% v. 2% O2 at all Ci values. In contrast, in the C3 species wheat there was a large O2 dependent increase in PS II quantum yield at low CO2, which reflects a high level of photorespiration. In the C4 plants, the relationship of the quantum yield of PS II electron transport to the quantum yield of CO2 fixation is linear suggesting that photochemical use of energy absorbed by PS II is tightly linked to CO2 fixation in C4 plants. This relationship is nearly identical in all three subgroups and may allow estimates of photosynthetic rates of C4 plants based on measurements of PS II photochemical efficiency. The results suggest that in C4 plants both the photoreduction of O2 and photorespiration are low, even at very limiting CO2 concentrations.

Physical, chemical, and regulatory properties of glycolate oxidase in C3 and C4 plants

2009 ◽  
Vol 56 (2) ◽  
pp. 164-167 ◽  
Author(s):  
A. T. Eprintsev ◽  
A. E. Semenov ◽  
M. Navid ◽  
V. N. Popov
Keyword(s):  
C4 Plants ◽  
Glycolate Oxidase ◽  
C3 And C4 Plants ◽  
Physical Chemical ◽  
Regulatory Properties
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