scholarly journals Isolation and properties of a ‘malic’ enzyme from cauliflower bud mitochondria

1971 ◽  
Vol 122 (4) ◽  
pp. 495-501 ◽  
Author(s):  
A. R. Macrae
Keyword(s):  
Malic Enzyme ◽  
Tricarboxylic Acid Cycle ◽  
Decarboxylase Activity ◽  
Enzyme Preparations ◽  
Ph Values ◽  
Low Concentrations ◽  
Absolute Requirement ◽  
Nad Oxidoreductase ◽  
Regulatory Properties

1. A ‘malic’ enzyme [l-malate–NAD oxidoreductase (decarboxylating), EC 1.1.1.39] has been isolated from cauliflower bud mitochondria and partially purified. 2. The enzyme is specific for l-malate and has an absolute requirement for either Mn2+, Co2+ or Mg2+. 3. The enzyme shows activity with both NAD+ and NADP+, but NAD+ is the preferred cofactor. 4. No appreciable oxaloacetate decarboxylase activity is present in the enzyme preparations even at low pH values. 5. The enzyme is inhibited by NADH and by oxaloacetate and stimulated by SO42− and by low concentrations of CoA. 6. The regulatory properties of the enzyme support the proposed role of the enzyme in the utilization of tricarboxylic acid-cycle acids for energy production when glycolysis is suppressed.

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.

scholarly journals Cloning of the Malic Enzyme Gene fromCorynebacterium glutamicum and Role of the Enzyme in Lactate Metabolism

2000 ◽  
Vol 66 (7) ◽  
pp. 2981-2987 ◽  
Author(s):  
Pierre Gourdon ◽  
Marie-France Baucher ◽  
Nic D. Lindley ◽  
Armel Guyonvarch
Keyword(s):  
Exponential Growth ◽  
Malic Enzyme ◽  
Tricarboxylic Acid Cycle ◽  
Physiological Role ◽  
Growth Period ◽  
Biochemical Properties ◽  
Lactate Metabolism ◽  
Wild Type ◽  
Malic Enzyme Gene

ABSTRACT Malic enzyme is one of at least five enzymes, known to be present in Corynebacterium glutamicum, capable of carboxylation and decarboxylation reactions coupling glycolysis and the tricarboxylic acid cycle. To date, no information is available concerning the physiological role of the malic enzyme in this bacterium. ThemalE gene from C. glutamicum has been cloned and sequenced. The protein encoded by this gene has been purified to homogeneity, and the biochemical properties have been established. Biochemical characteristics indicate a decarboxylation role linked to NADPH generation. Strains of C. glutamicum in which themalE gene had been disrupted or overexpressed showed no detectable phenotype during growth on either acetate or glucose, but showed a significant modification of growth behavior during lactate metabolism. The wild type showed a characteristic brief period of exponential growth on lactate followed by a linear growth period. This growth pattern was further accentuated in a malE-disrupted strain (ΔmalE). However, the strain overexpressingmalE maintained exponential growth until all lactate had been consumed. This strain accumulated significantly larger amounts of pyruvate in the medium than the other strains.

scholarly journals Identification of In Vivo Enzyme Activities in the Cometabolism of Glucose and Acetate by Saccharomyces cerevisiae by Using 13C-Labeled Substrates

2003 ◽  
Vol 2 (3) ◽  
pp. 599-608 ◽  
Author(s):  
Margarida Moreira dos Santos ◽  
Andreas Karoly Gombert ◽  
Bjarke Christensen ◽  
Lisbeth Olsson ◽  
Jens Nielsen
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Enzyme Activities ◽  
Malic Enzyme ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Tricarboxylic Acid Cycle ◽  
Central Carbon Metabolism ◽  
Isopropylmalate Synthase ◽  
Very High

ABSTRACT A detailed characterization of the central metabolic network of Saccharomyces cerevisiae CEN.PK 113-7D was carried out during cometabolism of different mixtures of glucose and acetate, using aerobic C-limited chemostats in which one of these two substrates was labeled with 13C. To confirm the role of malic enzyme, an isogenic strain with the corresponding gene deleted was grown under the same conditions. The labeling patterns of proteinogenic amino acids were analyzed and used to estimate metabolic fluxes and/or make inferences about the in vivo activities of enzymes of the central carbon metabolism and amino acid biosynthesis. Malic enzyme flux increased linearly with increasing acetate fraction. During growth on a very-high-acetate fraction, the activity of malic enzyme satisfied the biosynthetic needs of pyruvate in the mitochondria, while in the cytosol pyruvate was supplied via pyruvate kinase. In several cases enzyme activities were unexpectedly detected, e.g., the glyoxylate shunt for a very-low-acetate fraction, phosphoenolpyruvate carboxykinase for an acetate fraction of 0.46 C-mol of acetate/C-mol of substrate, and glucose catabolism to CO2 via the tricarboxylic acid cycle for a very-high-acetate fraction. Cytoplasmic alanine aminotransferase activity was detected, and evidence was found that α-isopropylmalate synthase has two active forms in vivo, one mitochondrial and the other a short cytoplasmic form.

scholarly journals Regulation of ‘malic’ enzyme of Solanum tuberosum by metabolites

1974 ◽  
Vol 137 (1) ◽  
pp. 45-53 ◽  
Author(s):  
D. D. Davies ◽  
K. D. Patil
Keyword(s):  
Solanum Tuberosum ◽  
Malic Enzyme ◽  
Energy Charge ◽  
Dicarboxylic Acids ◽  
Oxidative Decarboxylation ◽  
Bivalent Cation ◽  
Ph Values ◽  
Rate Versus ◽  
Reductive Carboxylation

A purification of ‘malic’ enzyme from potato is described. The purified enzyme is specific for NADP and requires a bivalent cation for activity. At pH values below 7 the plot of rate versus malate concentration approximates to normal Michaelis–Menten kinetics. At pH values above 7 the plot of rate versus malate concentration is sigmoid. A number of dicarboxylic acids activate the enzyme and remove the sigmoidicity. The enzyme is inhibited by phosphate, triose phosphates and AMP. In general, effectors of the oxidative decarboxylation of malate behave in the same manner in the reductive carboxylation of pyruvate. The response of the enzyme to energy charge is reported and the physiological significance of the response to metabolites is discussed in relation to the proposed role of the enzyme in the control of pH.

Testosterone Potentiation of Ionophore and ADP Induced Platelet Aggregation : Relationship to Arachidonic Acid Metabolism

1981 ◽  
Vol 46 (02) ◽  
pp. 538-542 ◽  
Author(s):  
R Pilo ◽  
D Aharony ◽  
A Raz
Keyword(s):  
Arachidonic Acid ◽  
Platelet Aggregation ◽  
Unsaturated Fatty Acids ◽  
Human Platelet ◽  
Platelet Rich Plasma ◽  
Arachidonic Acid Metabolism ◽  
Ionophore A23187 ◽  
Low Concentrations ◽  
Induced Aggregation

SummaryThe role of arachidonic acid oxygenated products in human platelet aggregation induced by the ionophore A23187 was investigated. The ionophore produced an increased release of both saturated and unsaturated fatty acids and a concomitant increased formation of TxA2 and other arachidonate products. TxA2 (and possibly other cyclo oxygenase products) appears to have a significant role in ionophore-induced aggregation only when low concentrations (<1 μM) of the ionophore are employed.Testosterone added to rat or human platelet-rich plasma (PRP) was shown previously to potentiate platelet aggregation induced by ADP, adrenaline, collagen and arachidonic acid (1, 2). We show that testosterone also potentiates ionophore induced aggregation in washed platelets and in PRP. This potentiation was dose and time dependent and resulted from increased lipolysis and concomitant generation of TxA2 and other prostaglandin products. The testosterone potentiating effect was abolished by preincubation of the platelets with indomethacin.

ZUR BEDEUTUNG DES HYPOPHYSÄREN LUTEINISIERUNGSHORMONS FÜR SCHWANGERSCHAFT, GEBURT UND LACTATION BEI DER RATTE

1970 ◽  
Vol 65 (3_Suppl) ◽  
pp. S5-S32 ◽  
Author(s):  
K. Loewit
Keyword(s):  
Luteinizing Hormone ◽  
Early Pregnancy ◽  
Hydroxysteroid Dehydrogenase ◽  
The State ◽  
Termination Of Pregnancy ◽  
Progesterone Level ◽  
Corpora Lutea ◽  
Regulatory Properties ◽  
Duration Of Pregnancy

ABSTRACT The role of luteinizing hormone (LH) for the maintenance of pregnancy, parturition and lactation was investigated by immunological and histochemical methods in the rat. Neutralisation of endogenous rat-LH with Rabbit-Anti-Bovine-LH-Serum (selective hypophysectomy) from days 7-12 of pregnancy resulted in reabsorption of the foetuses and the reappearance of strong 20α-hydroxysteroid-dehydrogenase (20α-OHSD) activity in the corpora lutea (CL) of pregnancy, which normally show no such activity at that time. This effect could be prevented in part by concurrent pregnenolone administration and fully by progesterone, but was not influenced by oestrogen or prolactin. It is concluded that in early pregnancy LH is the main luteotrophic hormone in the rat even though prolactin might act synergistically with it. Antiserum treatment after the 12th day of gestation had no influence on the state or duration of pregnancy or on parturition. LH-injections during the first half of pregnancy had no luteolytic effects i. e. they did not activate 20α-OHSD activity. After day 16 they advanced the reappearance of the enzyme, but delayed parturition or resulted in stillbirths. Neither LH nor antiserum seemed to alter lactation. Since progesterone prevented both the termination of pregnancy and the recurrence of 20α-OHSD activity, it should have some regulatory properties on the enzyme. It is discussed whether the gonadotrophin-dependent progesterone level could regulate the 20α-OHSD activity rather than result from it.

scholarly journals The role of malic enzyme in the regulation of lipid accumulation in filamentous fungi

Microbiology ◽  
1999 ◽  
Vol 145 (8) ◽  
pp. 1911-1917 ◽  
Author(s):  
James P. Wynn ◽  
Aidil bin Abdul Hamid ◽  
Colin Ratledge
Keyword(s):  
Filamentous Fungi ◽  
Lipid Accumulation ◽  
Malic Enzyme

scholarly journals The Role of Cell Metabolism in Innate Immune Memory

2020 ◽  
pp. 1-9
Author(s):  
Anaisa Valido Ferreira ◽  
Jorge Domiguéz-Andrés ◽  
Mihai Gheorghe Netea
Keyword(s):  
Metabolic Pathways ◽  
Tricarboxylic Acid Cycle ◽  
Cell Metabolism ◽  
Innate Immune ◽  
Immune Memory ◽  
Functional Changes ◽  
Trained Immunity ◽  
Health And Disease

Immunological memory is classically attributed to adaptive immune responses, but recent studies have shown that challenged innate immune cells can display long-term functional changes that increase nonspecific responsiveness to subsequent infections. This phenomenon, coined <i>trained immunity</i> or <i>innate immune memory</i>, is based on the epigenetic reprogramming and the rewiring of intracellular metabolic pathways. Here, we review the different metabolic pathways that are modulated in trained immunity. Glycolysis, oxidative phosphorylation, the tricarboxylic acid cycle, amino acid, and lipid metabolism are interplaying pathways that are crucial for the establishment of innate immune memory. Unraveling this metabolic wiring allows for a better understanding of innate immune contribution to health and disease. These insights may open avenues for the development of future therapies that aim to harness or dampen the power of the innate immune response.

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