Properties of Phosphoenolpyruvate Carboxykinase Operative in C4 Pathway Photosynthesis

1977 ◽  
Vol 4 (2) ◽  
pp. 207 ◽  
Author(s):  
MD Hatch ◽  
S Mau
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Reverse Direction ◽  
Nucleoside Triphosphate ◽  
Dihydroxyacetone Phosphate ◽  
C4 Pathway ◽  
Phosphoglyceric Acid ◽  
Michaelis Constants ◽  
Chloris Gayana ◽  
Fructose 1,6 Bisphosphate ◽  
Chloris Gayana Kunth

A procedure is described for partially purifying phosphoenolpyruvate carboxykinase [ATP : oxaloacetate carboxy-lyase (transphosphorylating), EC 4.1.1.49] from leaves of Chloris gayana Kunth. In three steps the enzyme was purified about 60-fold with 22% recovery of activity. This procedure removes enzymes, particularly malate dehydrogenase, that preclude the use of a simple spectrophotometric assay for phosphoenolpyruvate carboxykinase. The activity of the enzyme in the direction of oxaloacetate decarboxylation was about 10 times that in the reverse direction. At the optimal pH of 8.0, ATP was the preferred nucleoside triphosphate but CTP, UTP, GTP and ITP were also active. A requirement for Mn2+ could not be replaced by Mg2+. The Michaelis constants for oxaloacetate and ATP were 0.035 mM and 0.024 nM, respectively. The photosynthetic intermediates fructose 1,6-bisphosphate, 3-phosphoglyceric acid and dihydroxyacetone phosphate significantly inhibited the enzyme at concentrations in the region of 1-5 mM. Unlike the phosphoenolpyruvate carboxykinase from other sources, the capacity of the leaf enzyme to catalyse the decarboxylation of oxaloacetate to pyruvate was negligible. The properties of the enzyme are discussed in relation to its proposed role in C4 pathway photosynthesis.

scholarly journals Triosephosphate isomerase deficiency: consequences of an inherited mutation at mRNA, protein and metabolic levels

2005 ◽  
Vol 392 (3) ◽  
pp. 675-683 ◽  
Author(s):  
Judit Oláh ◽  
Ferenc Orosz ◽  
László G. Puskás ◽  
László Hackler ◽  
Margit Horányi ◽  
...  
Keyword(s):  
Steady State ◽  
Triosephosphate Isomerase ◽  
Specific Activity ◽  
Energy State ◽  
Dihydroxyacetone Phosphate ◽  
Peptidase Activity ◽  
Mrna Levels ◽  
Regulatory Enzymes ◽  
Computational Data ◽  
Fructose 1,6 Bisphosphate

Triosephosphate isomerase (TPI) deficiency is a unique glycolytic enzymopathy coupled with neurodegeneration. Two Hungarian compound heterozygote brothers inherited the same TPI mutations (F240L and E145Stop), but only the younger one suffers from neurodegeneration. In the present study, we determined the kinetic parameters of key glycolytic enzymes including the mutant TPI for rational modelling of erythrocyte glycolysis. We found that a low TPI activity in the mutant cells (lower than predicted from the protein level and specific activity of the purified recombinant enzyme) is coupled with an increase in the activities of glycolytic kinases. The modelling rendered it possible to establish the steady-state flux of the glycolysis and metabolite concentrations, which was not possible experimentally due to the inactivation of the mutant TPI and other enzymes during the pre-steady state. Our results showed that the flux was 2.5-fold higher and the concentration of DHAP (dihydroxyacetone phosphate) and fructose 1,6-bisphosphate increased 40- and 5-fold respectively in the erythrocytes of the patient compared with the control. Although the rapid equilibration of triosephosphates is not achieved, the energy state of the cells is not ‘sick’ due to the activation of key regulatory enzymes. In lymphocytes of the two brothers, the TPI activity was also lower (20%) than that of controls; however, the remaining activity was high enough to maintain the rapid equilibration of triosephosphates; consequently, no accumulation of DHAP occurs, as judged by our experimental and computational data. Interestingly, we found significant differences in the mRNA levels of the brothers for TPI and some other, apparently unrelated, proteins. One of them is the prolyl oligopeptidase, the activity decrease of which has been reported in well-characterized neurodegenerative diseases. We found that the peptidase activity of the affected brother was reduced by 30% compared with that of his neurologically intact brother.

scholarly journals Fructose 1,6-bisphosphate aldolase from rabbit muscle. The isomerization of the enzyme-dihydroxyacetone phosphate complex

1977 ◽  
Vol 167 (2) ◽  
pp. 361-366 ◽  
Author(s):  
E Grazi ◽  
M Blanzieri
Keyword(s):  
Competitive Inhibitor ◽  
Dihydroxyacetone Phosphate ◽  
Rabbit Muscle ◽  
Keto Form ◽  
First Order ◽  
Phosphate Complex ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Dead End ◽  
Fructose 1,6 Bisphosphate

The formation and dissociation of the aldolase-dihydroxyacetone phosphate complex were studied by following changes in A240 [Topper, Mehler & Bloom (1957), Science 126, 1287-1289]. It was shown that the enzyme-substrate complex (ES) slowly isomerizes according to the following reaction: (formula: see text) the two first-order rate constants for the isomerization step being k+2 = 1.3s-1 and k-2 = 0.7s-1 at 20 degrees C and pH 7.5. The dissociation of the ES complex was provoked by the addition of the competitive inhibitor hexitol 1,6-bisphosphate. At 20 degrees C and pH 7.5, k+1 was 4.7 X 10(6)M-1-S-1 and k-1 was 30s-1. Both the ES and the ES* complexes react rapidly with 1.7 mM-glyceraldehyde 3-phosphate, the reaction being practically complete in 40 ms. This shows that the ES* complex is not a dead-end complex. Evidence was also provided that aldolase binds and utilizes only the keto form of dihydroxyacetone phosphate.

Verteilung und Wanderung von Phosphoglycerat zwischen den Chloroplasten und dem Cytoplasma während der Photosynthese

1965 ◽  
Vol 20 (9) ◽  
pp. 890-898 ◽  
Author(s):  
W. Urbach ◽  
M. A. Hudson ◽  
W. Ullrich ◽  
K. A. Santarius ◽  
U. Heber
Keyword(s):  
Turnover Rate ◽  
Rapid Decrease ◽  
Permeability Barrier ◽  
Dihydroxyacetone Phosphate ◽  
Cyanide Poisoning ◽  
Similar Extent ◽  
Slow Increase ◽  
Phosphoglyceric Acid ◽  
Inhibition Of Metabolism ◽  
Isolated Chloroplasts

The distribution of phosphoglyceric acid (PGA) * between chloroplasts and cytoplasm of leaf cells during transients from dark to light and vice versa has been investigated. The data indicate that pools of PGA in the chloroplasts and cytoplasm are interchangeable and that PGA may function as a transport metabolite in actively metabolising leaf cells. These views are supported by the following results:1. In the presence of 14CO2 and light, labelled PGA rapidly appears in the cytoplasm, even though the carboxydismutase reaction, in which 14C enters into PGA, proceeds in the chloroplasts.2. After less than 1 min. illumination in the presence of 14CO2, the distribution of labelled PGA between chloroplasts and cytoplasm reaches an equilibrium, which is then maintained. The same distribution is to be found by enzymatic analyses of the total pools of PGA in chloroplasts and cytoplasm. When equilibrium is reached, the percentages of both 14C labelled and of total PGA to be found in the chloroplasts of Spinach and Elodea are approximately 75% and 35 —40% respectively.3. In both the chloroplasts and the cytoplasm, the levels of PGA first decrease after illumination to a fraction of the original dark levels and then show a concomitant slow increase. On darkening a further very rapid increase in PGA occurs in chloroplasts and cytoplasm.4. In photosynthetically active leaf material the rate of decrease in the level of cytoplasmic PGA, as observed after 12 —15 secs. illumination, is higher than the turnover rate of PGA in respiration.5. Upon illumination, aqueously isolated chloroplasts, suspended in isotonic sucrose buffer, reduce added PGA to dihydroxyacetone phosphate and other products far faster than they reduce added NADP. Whereas PGA reduction is not increased by ultrasonic disintegration of the chloroplasts, the reduction of NADP is stimulated. This indicates that whereas the movement of NADP is prevented by a permeability barrier, the transferance of PGA across the chloroplast membrane occurs easily.6. In illuminated Elodea shoots the inhibition of metabolism by cyanide after 15 secs. photosynthesis in the presence of Η14CO3⊖ leads to a rapid decrease in PGA. This applies to both the 14C labelled PGA and the total PGA to a similar extent. The decrease in PGA amounts from 70 — 85% of the original dark levels. Since the chloroplasts of Elodea contain only 35—40% of the total PGA of the cell, a fall in the level of PGA as a result of the cyanide poisoning obviously occurs not only in the chloroplasts, but also in the cytoplasm. Since cyanide effectively inhibits cytochrome oxidase, while PGA reduction in the chloroplasts is relatively resistant, the large decrease in PGA suggests that part of the cytoplasmic PGA is transferred into the chloroplasts and reduced there.

Effects of flood irrigation and plant growth on two riverine soils

1959 ◽  
Vol 10 (4) ◽  
pp. 510 ◽  
Author(s):  
KP Barley ◽  
AL Tisdall
Keyword(s):  
Plant Growth ◽  
Exchangeable Sodium ◽  
Flood Irrigation ◽  
Nitrogen And Phosphorus ◽  
Rhodes Grass ◽  
Water Stable Aggregates ◽  
Electrolyte Content ◽  
Chloris Gayana ◽  
The Stability ◽  
Chloris Gayana Kunth

Two soils which contained significant proportions of exchangeable sodium were frequently irrigated during summer with water of low electrolyte content. When all vegetation was removed the soils became very unstable in water. When the natural vegetation was left intact the stability and structure of the soils did not deteriorate despite frequent irrigation. When the amount of vegetation was increased by sowing Rhodes grass (Chloris gayana Kunth) and supplying nitrogen and phosphorus the stability of the soil increased. After 8 years' growth of Rhodes grass the top inch of soil contained 30–40 per cent. of water-stable aggregates greater than 1 mm in diameter, compared with a content of 10–20 per cent. in virgin soil. Thus, the protective effect of the organic matter added to the soil by plant growth more than compensated for aggregate disruption caused by flood wetting or by a reduction in electrolyte content of the soil solution.

A study of two strains of Rhodes Grass (Chloris gayana Kunth.) and of Leucerne (Medicago sativa L.) as components of a mixed pasture at Lawes in South-east Queensland

1952 ◽  
Vol 3 (3) ◽  
pp. 277 ◽  
Author(s):  
CS Christian ◽  
NH Shaw
Keyword(s):  
Medicago Sativa ◽  
Growth Form ◽  
Live Weight ◽  
Small Population ◽  
Rhodes Grass ◽  
Weight Gains ◽  
Chloris Gayana ◽  
Medicago Sativa L ◽  
Chloris Gayana Kunth

The results of investigations with Rhodes grass and lucerne as components of sown pastures at Lawes in south-east Queensland are reported. Two strains of Rhodes grass, differing very markedly in growth form, rate of maturity, and other characteristics, were shown to be virtually of the same value when grazed by cattle under a system of intermittent grazing at a heavy rate of stocking. It was shown that lucerne could be maintained in a mixed pasture with Rhodes grass, and that the presence of a small population of lucerne, of a density of 2-4 plants per square yard, resulted in Increased growth of Rhodes grass and increased live-weight gains by the steers. Reasons for these increases are discussed.It is considered that the mixture, which can be expected to give improved grazing mainly during the summer months, has possibilities for large areas in south-east Queensland.

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.

Triosephosphate metabolism by mature boar spermatozoa

1997 ◽  
Vol 9 (6) ◽  
pp. 577 ◽  
Author(s):  
A. R. Jones
Keyword(s):  
Glycolytic Pathway ◽  
Dihydroxyacetone Phosphate ◽  
Glycolytic Intermediates ◽  
Boar Sperm ◽  
Equilibrium Concentrations ◽  
Fructose 1,6 Bisphosphate ◽  
Boar Spermatozoa

Boar sperm rapidly interconverted dihydroxyacetone phosphate and glyceraldehyde 3-phosphate, produced fructose-1,6-bisphosphate, approximately equilibrium concentrations of fructose 6-phosphate and glucose 6-phosphate but not glycerol or glycerol 3-phosphate. In the presence of 3-chloro-1-hydroxypropanone, an inhibitor of stage 2 of the glycolytic pathway, the triosephosphates were metabolized faster, produced less fructose-1,6-bisphosphate, fructose 6-phosphate and glucose 6-phosphate, but not glycerol or glycerol 3-phosphate. This suggests that these cells may have the capacity to convert glycolytic intermediates into a storage metabolite to conserve carbon atoms for the eventual synthesis of lactate.

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