Effect of light on the formation of multiple molecular forms of glutamine synthetase in plants

Summary The presence of multiple molecular forms (MMF) of glutamine synthetase (GS) has been studied in pumpkin plants and in cotyledons of bean plants. Two MMF of GS have been found in pumpkin leaves and in green cotyledons: chloroplast GS and cytosol GS. Cotyledons of etiolated pumpkin seedlings contain only the cytosol GS. Illumination of etiolated pumpkin seedlings with white light results in the appearance, within one minute, of the second molecular form, the chloroplast GS, which appears to be due to activation rather than de novo synthesis of the enzyme. Cotyledons of resting seeds of horse bean, pea, soybean and lupine contain only one form of GS. The second form, chloroplast GS, appears after germination in the light, but only in those cotyledons of soybean and lupine that can become green.     

Synthesis of 5,8,11,14,17-eicosapentaenic acid

A synthetic route to 5,8,11,14,17-eicosapentaynoic acid, an acetylenic precursor of 5Z,8Z,11Z,14Z,17Z-eicosapentaenoic acid, has been developed based on condensation of a propargyl synthon with omega-acetylenic fragments. Physico-chemical constants and spectral characteristics (IR, 1H-NMR, and mass-spectrometry) of the target and intermediate compounds are given.     

Mechanism of action of vitamin E. Study of the interaction of vitamin E (alpha-tocopherol) and its analogs with fatty acids and their derivatives by fluorimetry]

Formation of a complex between alpha-tocopherol or its analogues in the excited state and fatty acids or their hydroperoxides has been suggested basing on the fluorescence quenching experimental data. The possible mechanism of the complex formation, its nature and role in the fatty acid peroxidation is discussed.     

Transformation products of vitamin E and its analog--chroman C1 in an oxidizing ethyl linoleate medium]

Spirodimers, dimers, quinones of alpha-tocopherol and chroman C1 have been synthesized by the alpha-tocopherol and chroman Ci oxidation with K3[Fe(CN)6] and FeCl3. Products of the oxidative transformation of alpha-tocopherol and chroman Ci, viz. dimers, quinones and trimers, in the media of ethyllinoleate and nonane have been identified by HPLC, TLC, UV, IR and 1H NMR spectroscopy. The mechanism of the transformation and modifying activity of chromans under various oxidation conditions are discussed with regards to the experimental data.     

A novel,stereospecific synthesis of β-D-glucopyranosyl phosphate

In alkaline solution, periodate ions form complexes with three consecutive hydroxyl groups in an axial-equatorial-axial arrangement but not with three syn-axial hydroxyl groups. Borate ions form complexes with three syn-axial hydroxyl groups but not with the axeqax sequence. Accordingly, cis-inositol gives a 1,2,3-periodate and a 1,3,5-borate complex. Cations form complexes with either type of conformation, but complex formation provides little energy towards achieving it by ring inversion. Lanthanide ions have been used to establish the sites of complex formation.     

Interaction of hemoglobin with phospholipid vesicular membranes of different composition

Incorporation of hemoglobin into vesicles and its oxidation were studied as a function of composition of the vesicular membrane containing erythrocyte membrane lipids as main components. The addition of negatively charged lipids such as phosphatidylserine and phosphatidic acid, was shown to considerably increase the extent of hemoglobin binding, while sphingomyelin did not produce such an effect. Cholesterol and dipalmitoylphosphatidylcholine stabilized oxyHb.     

Purification and physico-chemical properties of glutamine synthetase from pea chloroplasts]

A highly purified, practically homogeneous glutamine synthetase was isolated from pea leaf chloroplasts. The enzyme purity was assayed by polyacrylamide gel electrophoresis and analytical ultracentrifugation. The sedimentation coefficient is 16,3S. The sedimentation equilibrium analysis showed that the molecular weight of the enzyme is equal to 480 000. The minimal molecular weights of the enzyme as calculated from the data of polyacrylamide gel electrophoresis in the presence of SDS and the amino acid analysis were found to be 62 000 and 60 000, respectively. The enzyme contains a large amount of dicarboxylic and sulfur-containing amino-acids. The N-terminal amino acid is glycine. The isoelectric point for the enzyme lies within the pH range of 4,2-4-4.     

Glutamine metabolism regulation in Chlorella pyrenoidosa. Regulation of Chlorella glutamine synthetase activity by amino acids]

Effect of glutamine and its metabolites (amino acids) on Chlorella glutamine synthetase (GS) (E.C.6.3.1.2) in the presence of Mg or Mn was studied. Purified GS preparation was used, isolated from Chlorella grown in the presence of NH as a sole nitrogen source. Glutamate, aspartate, alanine and glycine inhibit GS activity in the presence of both Mg and Mn. Tryptophane and valine (up to 15 mM) activate GS in the presence of Mn. Tryptophane inhibits GS in the system with Mg. Sinergistic inhibition was observed under the combined effect of amino acids on GS in the presence of Mn and aspartate or alanine. The change of GS activity observed is supposed to be due to the inhibitory effect of glutamine and amino acids studied, since the glutamine content is increased (in 2.5 times for 5 min) and that of alanine and dicarbonic amino acids (for the following 15 min) under NH assimilation in Chlorella cells.