Cytosolic malate dehydrogenase in muscle extracts of Toxocara canis

1. Malate dehydrogenase (L-malic acid:NAD+ oxydoreductase, EC 1.1.1.37) was partially purified from muscle extracts of Toxocara canis by means of gel chromatography in Sephadex G-150 and affinity chromatography in Sepharose-4B-Blue dextran. 2. The purified enzyme was very active in reducing oxalacetate and less active in oxidizing L-malate. It was inhibited by excess oxalacetate but not by L-malate. 3. The kinetic parameters of the enzyme were obtained and these included: pH and temperature optima and apparent Michaelis constants for the substrates. 4. The results suggest that the enzyme from Toxocara canis behaves like the enzyme of the model helminth Ascaris lumbricoides.

Rat brain malic enzyme: subcellular distribution and kinetic studies from two brain regions

1. The subcellular distribution of malic enzyme in two different brain regions (frontal cortex and striatum) is studied in adult rats. 2. A bimodal distribution is found in both regions: 75% being localized in the mitochondrial fraction and the remaining 25% in the cytosol. 3. In the frontal cortex, free mitochondria is enriched with the enzyme, while, in striatum, free as well as synaptic mitochondria, presented the same activity. 4. Kinetic studies of the malic enzymes show two Km values when malate is used as substrate. A higher Km value for free mitochondria as compared with a lower one found for the cytosolic and synaptosomal mitochondria suggests the presence of two enzyme populations. 5. The following are common characteristics for the two enzyme populations: NADP dependence, use of either Mg2+ or Mn2+ as cofactor and hyperbolic malate saturation curves not affected by dicarboxylic acids.

Adaptative features of ectothermic enzymes--IV. Studies on malate dehydrogenase of Astyanax fasciatus (Characidae) from Lobo Reservoir (Såo Carlos, Såo Paulo, Brasil)

1. Skeletal muscle and heart supernatant malate dehydrogenase (s-MDH) from a subtropical fish, Astyanax fasciatus consists of three electrophoretically anodal bands. Each band is a dimer (AA, AB and BB) and two loci are active. 2. In A. fasciatus tissue extracts, A and B subunits are present at differing quantitative levels and their activities are almost season-independent. However, the relative activity of each homodimer in relation to total s-MDH estimated by densitometry of gels or of each homodimer purified by chromatography varies with temperature. The more anodic homodimer is thermolabile and the less anodic one is thermostable. 3. The pH optimum of s-MDH is 7.5, of AA is 6.5 and of BB is 7.8. 4. The BB isozyme is more sensitive to high concentrations of substrate and has a Km temperature-independent. The AA isozyme is not inhibited by high concentrations of oxaloacetate and shows a Km temperature-dependent with a fourteenfold increase between 20 degrees and 40 degrees C.

Mitochondrial malic enzymes. Purification and properties of the NAD(P)-dependent malic enzyme from canine small intestinal mucosa

An NAD(P)-dependent malic enzyme with a specific activity of 40.6 mumol of NADH/min/mg of protein and an isoelectric point of 5.4 was purified to apparent homogeneity from canine small intestinal mucosal mitochondria. The purification procedure employed ammonium sulfate fractionation, Sepharose CL 6B gel filtration, chromatography on DEAE-cellulose to remove the interfering malate dehydrogenase, and affinity chromatography on 2',5'-ADP-Sepharose and NAD-agarose to take advantage of the dual coenzyme specificity. Antibody prepared from the purified enzyme produced a single peak upon cross-rocket immunoelectrophoresis against the mitochondrial sonicate. Continuous polyacrylamide gel electrophoresis showed NAD and NADP activity co-migrating with the native protein band. A single band of protein having an apparent Mr = 62,000 was seen on sodium dodecyl sulfate electrophoresis. At pH 7.3, gel filtration revealed a single peak of activity with NAD and NADP corresponding to an apparent Mr = 282,000. Gradient gel polyacrylamide electrophoresis at pH 9.0 indicated an additional broad band of activity corresponding to a Mr = 141,000. Under physiological conditions therefore the protein appears to exist as a tetramer of Mr = 282,000 composed of four equal subunits, whereas at elevated pH values during electrophoresis, partial dissociation to a dimeric species occurs.

The rapid purification of 3-hydroxybutyrate dehydrogenase and malate dehydrogenase on triazine dye affinity matrices

3-Hydroxybutyrate dehydrogenase (EC 1.1.1.30) and malate dehydrogenase (EC 1.1.1.37) were purified to homogeneity on a large scale involving only two sequential affinity-chromatography steps on two triazine dye-Sepharose matrices. Recoveries of both enzymes were in excess of 60%. Malate dehydrogenase could also be purified by a combination of triazine dye affinity chromatography and gel filtration on Ultrogel AcA-44, but this offered no significant advantage over the purely affinity procedure.

[Multiple molecular forms of "malic" enzyme from zea mays leaves]

Using 7.5% polyacrylamide gel electrophoresis, a heterogeneity of molecular forms of "malic" enzyme (EC 1.1.1.40) in corn leaves was established. Etyolated corn sprouts contain only one component of the enzyme, while in the green leaves 3 minor components were additionally found. A possible existence of the "malic" enzyme in two forms, a compact and a dissociating ones, is postulated. In comparison with the compact form the dissociating form of the enzyme is more active and possesses additional functional properties due to the presence of minor components.

The anaerobic metabolism of malate of Saccharomyces bailii and the partial purification and characterization of malic enzyme

1. The main pathway of the anaerobic metabolism of L-malate in Saccharomyces bailii is catalyzed by a L-malic enzyme. 2. The enzyme was purified more than 300-fold. During the purification procedure fumarase and pyruvate decarboxylase were removed completely, and malate dehydrogenase and oxalacetate decarboxylase were removed to a very large extent. 3. Manganese ions are not required for the reaction of malic enzyme of Saccharomyces bailii, but the activity of the enzyme is increased by manganese. 4. The reaction of L-malic enzyme proceeds with the coenzymes NAD and (to a lesser extent) NADP. 5. The Km-values of the malic enzyme of Saccharomyces bailii were 10 mM for L-malate and 0.1 mM for NAD. 6. A model based on the activity and substrate affinity of malic enzyme, the intracellular concentration of malate and phosphate, and its action on fumarase, is proposed to explain the complete anaerobic degradation of malate in Saccharomyces bailii as compared with the partial decomposition of malate in Saccharomyces cerevisiae.

D-Malic enzyme of Pseudomonas fluorescens

By the enrichment culture technique 14 gram-negative bacteria and two yeast strains were isolated that used D(+)-malic acid as sole carbon source. The bacteria were identified as Pseudomonas putida, Pseudomonas fluorescens, Pseudomonas aeruginosa and Klebsiella aerogenes. In cell-free extracts of P. fluorescens and P. putida the presence of malate dehydrogenase, D-malic enzyme (NAD-dependent) and L-malic enzyme (NADP-dependent) was demonstrated. D-Malic enzyme from P. fluorescens was purified. Stabilization of the enzyme by 50 mM ammonium sulphate an 1 mM EDTA was essential. Preparation of D-malic enzyme that gave one band with disc gel electrophoresis showed a specific activity of 4-5 U/mg. D-Malic enzyme requires divalent cations. The Km values were for malate Km = 0.3 mM and for NAD Km = 0.08 mM. The pH optimum for the reaction was found to be in the range of pH 8.1 to pH 8.8. D-Malic enzyme is partially inhibited by oxaloacetic acid, meso-tartaric acid, D-lactic acid and ATP. Determined by gel filtration and gradient gel electrophoresis, the molecular weight was approximately 175 000.

Unusual behaviour of NADP-linked malic enzyme from crustacean tissues on 2',5' ADP-Sepharose 4B

1. Essential differences in the binding of NADP-dependent malic enzymes from mammals, fish and crustacea to 2',5' ADP-Sepharose 4B have been shown. 2. The enzymes from mammalian and fish tissues interact with 2',5' ADP-Sepharose, whereas the enzymes from crayfish Orconectes limosus and shrimp Crangon crangon tissues do not. 3. These results provide evidence that 2',5' ADP-Sepharose cannot be used for the purification of NADP-dependent malic enzyme from crayfish and shrimp and indicate presumably a structural difference in the NADP-binding site of crustacean enzyme.

Inhibition of NADP-linked malic enzyme from Onchocerca volvulus and Dirofilaria immitis by suramin

NADP-linked malic enzyme (malate dehydrogenase (oxaloacetate-decarboxylating) NADP+, EC 1.1.1.40) has been partially purified from adult Onchocerca volvulus and Dirofilaria immitis. Suramin was found to inhibit the activity of malic enzyme from both filarial worms. The inhibition constants for suramin were calculated to be 0.011 microM and 0.015 microM for the enzymes from O. volvulus and D. immitis, respectively. In the case of NADP-linked malic enzyme from Trypanosoma brucei and chicken liver the inhibition by suramin was less pronounced. The inhibition constants were found to be 0.8 microM and 2.5 microM for the protozoan and vertebrate enzymes, respectively. The type of inhibition was competitive with respect to malate. The Michaelis constants for malate and pyruvate were determined to be 0.9 and 4.5 mM for O. volvulus and 0.85 and 5.0 mM for D. immitis, respectively. The low Km values for malate compared to those for pyruvate and the about 15-fold greater turnover in the direction of decarboxylation compared to carboxylation indicated that malic enzyme from both filarial sources might be involved in an alternative pathway leading from phosphoenolpyruvate via oxaleacetate, malate and pyruvate to lactate. It is suggested, that the inhibition of malic enzyme activity from O. volvulus by suramin might interfere with the generation of NADPH for biosynthetic reactions.

Thermostable, ammonium-activated malic enzyme of Clostridium thermocellum

"Malic" enzyme (L-malate:NADP+ oxidoreductase (oxaloacetate-decarboxylating, EC 1.1.1.40) was purified from Clostridium thermocellum by DEAE-cellulose, agarose-NADP and Sephadex G-200 column chromatography. The 117-fold purified "malic" enzyme displayed a maximum activity of 135 units/mg at 40 degrees C and represented 0.8% of the total cell protein. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis analysis of the protein suggested 90% purity and an approximate tetrameric subunit molecular weight of 40 000. The enzyme absolutely required both bivalent and monovalent cations for catalysis. Mn2+ and NH4+ were the most effective cationic activators examined. Increasing NH4+ concentration increased both enzyme activity and affinity toward L-malate. The apparent Km for L-malate was 3 X 10(-4) M at 0.4 mM NH4Cl. Enzyme activity increased linearly when temperature was raised between 22-60 degrees C and a Q10 of 2.1 was calculated from an Arrhenius plot. The enzyme was stable at heating at 60 degrees C but was denatured at higher temperatures. The enzyme half-life was 10 min at 72 degrees C. The enzyme displayed a broad pH optimum (7.2-87.2 for Tris-HCl buffer) but was inactivated by p-chloromercuribenzoate. The high thermal stability, low apparent molecular weight and NH4+ activation are properties not common to all previously described "malic" enzymes.

Malate dehydrogenase: isolation from E. coli and comparison with the eukaryotic mitochondrial and cytoplasmic forms

Escherichia coli malate dehydrogenase has been isolated in homogeneous form by a procedure employing chromatography on DEAE-cellulose, 5-'AMP-Sepharose, and Sephacryl-200. It is composed of two identical polypeptide chains each of Mr = 32 500. Like porcine mitochondrial malate dehydrogenase, it is devoid of tryptophan, but otherwise it is not particularly more similar in composition to one of the eukaryotic isozymes than to the other. However, amino-terminal sequence analysis of the first 36 residues shows remarkable similarity of the bacterial and mitochondrial enzymes (69% identical residues) in contrast to the cytoplasmic form (27%). The two porcine heart enzymes are identical in 24% of the positions compared. These results clearly establish that all three forms of malate dehydrogenase have evolved from a common precursor and that the prokaryotic and mitochondrial forms have retained sequences that are much closer to the ancestral one than the cytoplasmic enzyme. These findings appear to further substantiate the endosymbiotic hypothesis for the origin of the mitochondrion.

Purification and regulatory properties of the NADP-linked malic enzyme for Crithidia fasciculata

The NADP-linked malic enzyme (EC 1.1.1.40) from the insect flagellate Crithidia fasciculata has been purified to electrophoretic homogeneity by a procedure involving ammonium sulphate fractionation, gel filtration on Sephadex G-200, and column chromatography on DEAE-cellulose and hydroxylapatite. The regulatory properties of the purified enzyme have been studied, and compared with those of the two forms malic enzyme (I and II) present in Trypanosoma cruzi. The enzyme from C. fasciculata, like malic enzyme II from T. cruzi was activated by L-aspartate and succinate, which decreased the apparent Km values for both substrates, L-malate and NADP; L-aspartate in addition increased the apparent Vmax. The enzyme from C. fasciculata was inhibited by oxaloacetate, which was strictly competitive towards L-malate, with an apparent Ki (26 microM) intermediate between those reported for the two enzyme forms from T. cruzi. The C. fasciculata enzyme, like malic enzyme II from T. cruzi, was inhibited by adenine nucleotides, which were competitive towards both substrates; in addition, it was inhibited by acetyl-CoA, glyoxylate and NADH, which affected very little the activity of both enzyme froms forms T. cruzi. Thus the malic enzyme from C. fasciculata showed a regulatory pattern even more complex than that of the same enzyme from T. cruzi, despite the fact that there seems to be only one enzyme, present in the cytosol, in the insect trypanosomatid.

Purification of malic enzyme from Ascaris suum using NAD+-agarose

Malic enzyme has been purified from Ascaris suum by polyethylene glycol precipitation, ion-exchange chromatography, ammonium sulfate precipitation, and NAD-agarose affinity chromatography to a specific activity of 80 units/mg (V/[E]t = 350 s-1). The preparation was shown to be homogeneous by SDS polyacrylamide disc gel electrophoresis. The procedure can be accomplished in a maximum of four days with a 74% yield.

Kinetic and physical properties of the L-malate-NAD+ oxidoreductase from Methanospirillum hungatii and comparison with the enzyme from other sources

The L-malate-NAD+ oxidoreductase of Methanospirillum hungatii was purified to homogeneity by using Blue Sepharose and ADP-Sepharose affinity chromatography. The molecular weight was estimated as 61 700 +/- 1900 by gel filtration and 64 200 +/- 1200 by ultracentrifugation. Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis indicated that the protein is composed of two polypeptide chains, each corresponding to 31 350 +/- 2150 daltons. Inhibition patterns obtained for malate, alpha-oxoglutarate and ADP established that the sequential reaction mechanism was ordered, with NADH serving as the first substrate. Intracellular concentrations of oxaloacetate approximated the Km value of 27 microM, but NADH was present at less than Km values. Comparison of the amino-acid composition of the L-malate-NAD+ oxidoreductase of M. hungatii and 22 others from prokaryotic and eukaryotic cells revealed a significant direct relationship between average hydrophobicity and the frequency of non-polar side chains, as well as a significant indirect relationship between average hydrophobicity and the polarity ratio. Calculations based on amino-acid-composition data indicated significant composition similarity between pairs of mammalian-cytoplasmic or pairs of mitochondrial L-malate-NAD+ oxidoreductases from various sources, but no significant composition similarity between any of the pairs of bacterial species examined.