Purification and properties of microbody malate dehydrogenase from Spinacia oleracea leaf tissue

Proteins involved in biophoton emission and flooding-stress responses in soybean under light and dark conditions

To know the molecular systems basically flooding conditions in soybean, biophoton emission measurements and proteomic analyses were carried out for flooding-stressed roots under light and dark conditions. Photon emission was analyzed using a photon counter. Gel-free quantitative proteomics were performed to identify significant changes proteins using the nano LC-MS along with SIEVE software. Biophoton emissions were significantly increased in both light and dark conditions after flooding stress, but gradually decreased with continued flooding exposure compared to the control plants. Among the 120 significantly identified proteins in the roots of soybean plants, 73 and 19 proteins were decreased and increased in the light condition, respectively, and 4 and 24 proteins were increased and decreased, respectively, in the dark condition. The proteins were mainly functionally grouped into cell organization, protein degradation/synthesis, and glycolysis. The highly abundant lactate/malate dehydrogenase proteins were decreased in flooding-stressed roots exposed to light, whereas the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme was increased in both light and dark conditions. Notably, however, specific enzyme assays revealed that the activities of these enzymes and biophoton emission were sharply increased after 3 days of flooding stress. This finding suggests that the source of biophoton emission in roots might involve the chemical excitation of electron or proton through enzymatic or non-enzymatic oxidation and reduction reactions. Moreover, the lysine ketoglutarate reductase/saccharopine dehydrogenase bifunctional enzyme may play important roles in responses in flooding stress of soybean under the light condition and as a contributing factor to biophoton emission.

Chromatographic behaviour of the molecular forms of guinea-pig skeletal muscle cytoplasmic malate dehydrogenase

The isolated molecular forms of guinea-pig skeletal muscle cytoplasmic malate dehydrogenase have a different chromatographic behaviour through affinity or hydrophobic interaction gels; in all cases the retention of the B form is more noticeable. Chromatography of a partly purified preparation through 5' AMP-Sepharose allows both molecular forms of malate dehydrogenase to be separated and obtained free from lactate dehydrogenase.

Metabolism and decarboxylation of glycollate and serine in leaf peroxisomes

The linked utilization of glycollate and L-serine has been studied in peroxisomal preparations from leaves of spinach beet (Beta vulgaris L.). The generation of glycine from glycollate was found to be balanced by the production of hydroxypyruvate from serine and similarly by 2-oxoglutarate when L-glutamate was substituted for L-serine. In the presence of L-malate and catalytic quantities of NAD(+), about 40% of the hydroxypyruvate was converted further to glycerate, whereas with substrate quantities of NADH, this conversion was almost quantitative. CO2 was released from the carboxyl groups of both glycollate and serine. Since the decarboxylation of both substrates was greatly in creased by the catalase inhibitor, 3-amino-1,2,4-triazole, and abolished by bovine liver catalase, it was attributed to the nonenzymic attack of H2O2, generated in glycollate oxidation, upon glyoxylate and hydroxypyruvate respectively. At 25-30° C, about 10% of the glyoxylate and hydroxypyruvate accumulated was decarboxylated, and the release of CO2 from each keto-acid was related to the amounts present. It is suggested that hydroxypyruvate decarboxylation might contribute significantly to photorespiration and provide a metabolic route for the complete oxidation of glycollate, the magnitude of this contribution depending upon the concentrations of glyoxylate and hydroxypyruvate in the peroxisomes.

Albumins, glyoxysomal enzymes and globulins in dry seeds of cucumis sativus: qualitative and quantitative analysis

1) Albumins and globulins were prepared from dry seeds of cucumbers (Cucumis sativus) by differential extraction. The globulin fraction was analyzed by gel electrophoresis under denaturing conditions in the presence and absence of mercaptoethanol. The subunit (Mr = 54000) of the tetramer (Mr = 240000) was shown to be composed of two different peptides. Microheterogeneity rendered the exact interpretation of the analysis difficult. 2) Glyoxysomal proteins were already present in dry seeds: malate synthase, isocitrate lyase, citrate synthase, malate dehydrogenase, catalase and crotonase could be detected unequivocally. It was demonstrated that the enzymatic and immunological properties of malate synthase and isocitrate lyase were not distinguishable from that of enzymes assigned to glyoxysomes of fully developed cotyledons. 3) Homogenates prepared from seeds by cautious cell disintegration were subjected to sucrose density gradient centrifugation and yielded microbody and protein body fractions, among other things.

Glyoxysomal and mitochondrial malate dehydrogenase of watermelon (Citrullus vulgaris) cotyledons : I. Molecular properties of the purified isoenzymes

Molecular properties of the glyoxysomal and mitochondrial isoenzyme of malate dehydrogenase (EC 1.1.1.37; L-malate: NAD(+) oxidoreductase) from watermelon cotyledons (Citrullus vulgaris Schrad.) were investigated, using completely purified enzyme preparations. The apparent molecular weights of the glyoxysomal and mitochondrial isoenzymes were found to be 67,000 and 74,000 respectively. Aggregation at high enzyme concentrations was observed with the glyoxysomal but not with the mitochondrial isoenzyme. Using sodium dodecyl sulfate electrophoresis each isoenzyme was found to be composed of two polypeptide chains of identical size (33,500 and 37,000, respectively). The isoenzymes differed in their isoelectric points (gMDH: 8,92, mMDH: 5.39), rate of heat inactivation (gMDH: τ1/2 at 40°C=3.0 min; mMDH: stable at 40°C; τ1/2 at 60°C=4.5 min), adsorption to dextran gels at low ionic strenght, stability against alkaline conditions and their pH optima for oxaloacetate reduction (gMDH: pH 6.6, mMDH: pH 7.5). Very similar pH optima, however, were observed for L-malate oxidation (pH 9.3-9.5). The results indicate that the glyoxysomal and mitochondrial MDH of watermelon cotyledons are distinct proteins of different structural composition.

Glyoxysomal and mitochondrial malate dehydrogenase of watermelon (Citrullus vulgaris) cotyledons : II. Kinetic properties of the purified isoenzymes

Kinetic parameters of the glyoxysomal and mitochondrial malate dehydrogenase (EC 1.1.1.37) of watermelon (Citrullus vulgaris Schrad.) cotyledons were compared. The data were obtained by initial rate experiments at pH 8.5 in both directions of the reaction using homogeneous enzyme preparations. Substrate inhibition at physiologically significant concentrations was observed with reduced nicotinamide adenine dinucleotide (NADH) (50% inhibition at 0.65 mmol·l(-1) NADH), but not with oxaloacetate, L-malate or oxidized nicotinamide adenine dinucleotide. The inhibition of both isoenzymes by 5'adenosine monophosphate was studied. Inhibition was found to be competitive with respect to NADH and non-competitive with respect to oxaloacetate. The apparent inhibitor constants at 200 μmol·l(-1) of the fixed substrates were 3.2 and 1.6 mmol·1(-1) for NADH, and 3.2 and 5.2 mmol·l(-1) for oxaloacetate with the glyoxysomal and mitochondrial isoenzymes, respectively. The energy of activation was determined for oxaloacetate reduction by glyoxysomal (E a =3.14×10(4)J×mol(-1)) and mitochondrial (E a =4.10×10(4) J x mol(-1)) MDH from Arrhenius plots, which exhibited constant slopes throughout the range of thermal stability.Despite considerable structural differences, the results indicate very similar kinetic behaviour of the glyoxysomal and mitochondrial isoenzymes. The physiological significance of the data are discussed in relation to the gluconeogenic processes occuring in cotyledons during germination.

Separation of malate dehydrogenase isoenzymes by affinity chromatography on 5'-AMP-Sepharose

The mitochondrial and glyoxysomal isoenzymes of malate dehydrogenase (EC 1.1.1.27) from watermelon cotyledons and the mitochondrial isoenzyme from pig heart adsorbed reversibly to 5'-AMP-Sepharose. They were specifically eluted with low concentrations of NADH rather than by NAD. In contrast, the cytoplasmic isoenzymes showed no affinity to the matrix-bound ligand. These binding properties are discussed in terms of structural and regulatory differences of the particulate and soluble malate dehydrogenase isoenzymes. Affinity chromatography on 5'-AMP-Sepharose significantly improved the purification of the particulate malate dehydrogenase isoenzymes with respect to homogeneity, yield, and the number of purification steps. In the case of the glyoxysomal isoenzyme it was the essential procedure to obtain complete purification of the enzyme.

Physical properties and chemical compositions of cytoplasmic and mitochondrial malate dehydrogenase from Physarum polycephalum

The malate dehydrogenase isoenzymes from Physarum polycephalum have been purified to homogeneity as confirmed by gel filtration chromatography, polyacrylamide gel disc electrophoresis and analytical ultracentrifugation. Certain physical and chemical parameters of the malate dehydrogenase isoenzymes reported here include sedimentation, molecular weight and subunit molecular weight. Most unique of the differences between the isoenzymes were the widely separate isoelectric points of 9.83 for mitochondrial malate dehydrogenase and 6.14 for the supernatant malate dehydrogenase. The amino acid analyses of each form were done revealing the isoenzymes were unquestionably unique proteins differing in the content of ten amino acids.