Molecular forms and kinetic properties of malate dehydrogenase and glutamate oxalacetate transaminase in Glenlea and Kharkov wheat cultivars

1989 ◽  
Vol 29 (4) ◽  
pp. 445-456 ◽  
Author(s):  
J.-P. Simon ◽  
M.-J. Peloquin ◽  
C. Charest
Keyword(s):  
Malate Dehydrogenase ◽  
Molecular Forms ◽  
Kinetic Properties ◽  
Wheat Cultivars ◽  
Glutamate Oxalacetate Transaminase

Molecular forms and kinetic properties of the mitochondrial fraction of NAD-malate dehydrogenase in four clones of Lathyrus japonicus (Leguminosae) from sites of contrasting climates

1986 ◽  
Vol 64 (11) ◽  
pp. 2675-2681 ◽  
Author(s):  
Jean-Pierre Simon
Keyword(s):  
Malate Dehydrogenase ◽  
Isoelectric Focusing ◽  
Marked Effect ◽  
Mitochondrial Fraction ◽  
Molecular Forms ◽  
Kinetic Properties ◽  
Cold Adapted ◽  
Isoelectric Points ◽  
Ph Range ◽  
Response To Temperature

The molecular forms and kinetic properties of the mitochondrial fraction of NAD-malate dehydrogenase (mt-MDH) were analyzed in four clonal populations of Lathyrus japonicus collected from sites of contrasting climates in eastern North America and acclimated to three experimental thermoperiods. Three molecular forms of mt-MDH were separated in eight different starch and acrylamide electrophoretic systems, and isoelectric focusing (IEF) disclosed nine isozymes with isoelectric points in the 6.7–8.2 pH range. No differences in the electrophoretic or isoelectric focusing patterns were observed between clones acclimated to any of the three thermoperiods. Apparent Km values and Vmax/Km ratios for oxalacetate were obtained at 14 assay temperatures ranging from 2.5 to 35 °C. Km values were lower in the 10–20 °C range and increased markedly at higher and, particularly, at assay temperatures below 10 °C. Acclimation had a marked effect upon Km values obtained at extreme assay temperatures. Km values were significantly higher for assays in the range of 30–35 °C for plants of the two cold-adapted clones grown at 7–15 °C and 15–25 °C. Vmax/Km ratios were lower over the 30–35 °C segment of the assay curve for mt-MDH of the two cold-adapted clones acclimated at 7–15 °C and 15–25 °C and acclimation modified the shape of the curves of Vmax/Km ratios for mt-MDH from the four clones. Results suggest that modifications in kinetic behaviour of mt-MDH among Lathyrus japonicus clones represent adjustments for the modulation of catalysis in response to temperature conditions at the original sites of collection of the clones.

Molecular forms and thermal and kinetic properties of purified glutathione reductase from two populations of barnyard grass (Echinochloa crus-galli(L.) Beauv.: Poaceae) from contrasting climatic regions in North America

2000 ◽  
Vol 78 (7) ◽  
pp. 969-980 ◽  
Author(s):  
Nadia Hakam ◽  
Jean-Pierre Simon
Keyword(s):  
Glutathione Reductase ◽  
Thermal Adaptation ◽  
Catalytic Efficiency ◽  
Molecular Forms ◽  
Kinetic Properties ◽  
Barnyard Grass ◽  
Climatic Regions ◽  
Two Populations ◽  
Menten Constant

The thermal, kinetic, and electrophoretic properties of purified glutathione reductase (GR; EC 1.6.4.2) were analyzed in plants from two ecotypes of barnyard grass (Echinochloa crus-galli (L.) Beauv.: Poaceae) originating from sites of contrasting climates in Quebec (QUE) and Mississippi (MISS). Crude and purified GR preparations from plants of both ecotypes consisted of one homodimer isomorph with the same electrophoretic mobility in polyacrylamide gels, a similar molecular mass for the native enzyme (98 kDa) and for each subunit of the dimer (44 kDa), and an identical pI of 5.9. The electrophoretic profile of GR purified from cold-acclimated plants at 14°C light (L) : 8°C dark (D) for 10 days was similar to that of GR from plants grown at 26°C L : 20°C D. Specific activities of purified GR from QUE plants were significantly higher than those of MISS plants. In vitro GR activities from QUE and MISS plants were not differentially affected by thermodenaturation at 55 or 65°C or by cold treatments at 2°C. Apparent energies of activation (Ea) of GR purified from QUE and MISS plants were similar with the exception of estimates of Ea(oxidized glutathione) for Q10(15-5°C) for which significantly lower values were obtained for QUE plants. No differences of physiological significance were observed for Km(Michaelis-Menten constant) values of GR purified from QUE and MISS plants. However, both Vmaxand Kcat(turnover numbers) estimates were significantly higher for GR purified from QUE plants over most of the range of assay temperatures, suggesting superior catalytic efficiency for the enzyme of the cold-adapted ecotype from Québec.Key words: barnyard grass, ecotypes, electrophoresis, enzyme kinetics, glutathione reductase, thermal adaptation.

scholarly journals Isoform expression in the multiple soluble malate dehydrogenase of Hoplias malabaricus (Erythrinidae, Characiformes)

2003 ◽  
Vol 63 (1) ◽  
pp. 7-15 ◽  
Author(s):  
M. R. Aquino-Silva ◽  
M. L. B. Schwantes ◽  
A. R. Schwantes
Keyword(s):  
Skeletal Muscle ◽  
Malate Dehydrogenase ◽  
Tandem Duplication ◽  
Carbon Flow ◽  
Substrate Affinity ◽  
Kinetic Properties ◽  
Thermal Stabilities ◽  
Hoplias Malabaricus ◽  
Isoform Expression

Kinetic properties and thermal stabilities of Hoplias malabaricus liver and skeletal muscle unfractionated malate dehydrogenase (MDH, EC 1.1.1.37) and its isolated isoforms were analyzed to further study the possible sMDH-A* locus duplication evolved from a recent tandem duplication. Both A (A1 and A2) and B isoforms had similar optima pH (7.5-8.0). While Hoplias A isoform could not be characterized as thermostable, B could as thermolabile. A isoforms differed from B isoform in having higher Km values for oxaloacetate. The possibly duplicated A2 isoform showed higher substrate affinity than the A1. Hoplias duplicated A isoforms may influence the direction of carbon flow between glycolisis and gluconeogenesis.

Adaptation and acclimation of higher plants at the enzyme level: thermal properties of NAD malate dehydrogenase of two species of Aster (Asteraceae) and their hybrid adapted to contrasting habitats

1980 ◽  
Vol 58 (13) ◽  
pp. 1474-1481 ◽  
Author(s):  
Luc Brouillet ◽  
Jean-Pierre Simon
Keyword(s):  
Malate Dehydrogenase ◽  
Higher Plants ◽  
Enzyme Level ◽  
Leaf Tissue ◽  
Forest Understory ◽  
Kinetic Properties ◽  
Peptidase Activity ◽  
Crude Extracts ◽  
Contrasting Habitats ◽  
Sphagnum Bog

Thermal and kinetic properties of NAD malate dehydrogenase (MDH) were investigated in clonal populations of two species of Aster and their hybrid: A. acuminatus, a forest understory species; A. nemoralis, a sphagnum-bog species; and A. blakei, their hybrid occurring at the bog–forest ecotone. The populations were collected within a 300 m radius in southwestern Quebec. Compared with A. acuminatus, the MDH of crude extracts from A. nemoralis had lower thermostability in both 5- and 10-min assays at 55 °C, and reduced apparent energy of activation (Ea) in the temperature range of 15–25 °C. However, these differences were not maintained in purified extracts of the species and may be attributed to higher phenolase and peptidase activity in crude extracts of A. nemoralis. The ratio of MDH activity over total protein concentration, or fresh weight leaf tissue, was higher in A. acuminatus than in A. nemoralis. Most values for these MDH properties of A. blakei were intermediate between those of the two parents. No differences, however, were observed for the substrate binding ability (Km) of MDH in the three taxa. Electrophoretic analyses show no qualitative differentiation in the enzyme profiles of MDH of the three taxa, which consist of two mitochondrial and six cytosolic isozymes. Mitochondrial isozymes were more thermostable but no differences in thermostability were observed among the forms of the species. The thermal and kinetic properties of malate dehydrogenase, as measured in situ, have not been substantially modified by the contrasting microclimatic regimes associated with the habitats of A. acuminatus and A. nemoralis.

scholarly journals Subcellular distribution and characterization of acetylcholinesterase activities from sheep platelets: relationships between temperature- dependence and environment

Blood ◽  
1990 ◽  
Vol 76 (4) ◽  
pp. 737-744
Author(s):  
J Sanchez-Yague ◽  
JA Cabezas ◽  
M Llanillo
Keyword(s):  
Acetylcholinesterase Activity ◽  
Break Point ◽  
Molecular Forms ◽  
Kinetic Properties ◽  
Multiple Molecular Forms ◽  
Key Enzyme ◽  
Membrane Bound ◽  
Hill Coefficients ◽  
Triton X

Acetylcholinesterase is a key enzyme in cholinergic neurotransmission for hydrolyzing acetylcholine and has been shown to possess arylacylamidase activity in addition to esterase activity. The enzyme is found at various loci, where its functional significance remains to be clarified, and it exists in multiple molecular forms. Sheep platelets have been shown to exhibit acetylcholinesterase activity associated with plasma membrane (Bp), endoplasmic reticulum (Cp), mitochondria granules (Dp), and soluble (As) fractions. These activities show differences in some physicochemical and kinetic properties. The soluble acetylcholinesterase is the most thermostable, and the enzyme from the Cp fractions shows the lowest affinity for the acetylthiocholine substrate and the strongest inhibition by fluoride. In all cases a noncompetitive inhibition of the enzyme by this ion is found. When membrane-bound acetylcholinesterases were assayed at temperatures between 12 degrees C and 33 degrees C, the Arrhenius plots of all activities exhibited a break point at about 17 degrees C. This discontinuity was abolished by addition of detergent to the assay medium (0.02% Triton X-100, final concentration). Their Hill coefficients were calculated in the presence of fluoride, showing unitary values in all cases, which points to a noncooperative effect and nonallosteric behavior in the particulate enzyme. These results suggest that the sheep platelet acetylcholinesterase associated with membrane-bound systems is modulated by the physical state of its environment, despite the fact that the enzyme might be lipid- or nonlipid-dependent.

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