Pyruvate metabolism in Halobacterium salinarium studied by intracellular 13C nuclear magnetic resonance spectroscopy.

13C nuclear magnetic resonance spectroscopy was used to study the metabolism of [2-13C]pyruvate in intact cells of Halobacterium salinarium. The spectra of these cells show that pyruvate is reduced to lactic acid and transaminated to alanine. The intensity of C-2 lactate is higher under anaerobic conditions than under aerobic conditions. When cells are grown in the absence of glucose, the level of C-2 lactate intensity is lower. In extracts of these cells, the level of NADH-dependent lactate dehydrogenase activity is lower than that of cells grown in the presence of glucose. A C-5 glutamate resonance suggests the entry of pyruvate into the tricarboxylic acid cycle through acetyl-coenzyme A. In addition, the label is also observed at C-3 and C-4 of glutamate, signifying a pyruvate carboxylase-type reaction and scrambling of label at the fumarate-succinate stage plus malic enzyme operation, respectively. Citrate synthase and malic enzyme activity appear to be controlled by the growth conditions of H. salinarium.     

Chemoenzymatic Route for the Synthesis of (S)‐Moprolol,a Potential β‐Blocker

A biocatalytic route for the synthesis of a potential β‐blocker, (S)‐moprolol is reported here. Enantiopure synthesis of moprolol is mainly dependent on the chiral intermediate, 3‐(2‐methoxyphenoxy)‐propane‐1,2‐diol. Various commercial lipases were screened for the enantioselective resolution of (RS)‐3‐(2‐methoxyphenoxy)propane‐1,2‐diol to produce the desired enantiomer. Among them, Aspergillus niger lipase (ANL) was selected on the basis of both stereo‐ and regioselectivity. The optimized values of various reaction parameters were determined such as enzyme (15 mg/mL), substrate concentration (10 mM), organic solvent (toluene), reaction temperature (30 °C), and time (18 h).The optimized conditions led to achieving >49% yield with high enantiomeric excess of (S)‐3‐(2‐methoxyphenoxy)propane‐1,2‐diol. The lipase‐mediated catalysis showed regioselective acylation with dual stereoselectivity. Further, the enantiopure intermediate was used for the synthesis of (S)‐moprolol, which afforded the desired β‐blocker. Chirality 28:313–318, 2016. © 2016 Wiley Periodicals, Inc.     

Isolation and characterization of adenosine kinase from Leishmania donovani

Adenosine kinase (ATP:adenosine 5'-phosphotransferase, EC 2.7.1.20) has been purified 3250-fold from Leishmania donovani promastigotes using ion-exchange, gel filtration, and affinity chromatography techniques. Both native and sodium dodecyl sulfate-gel electrophoresis of the enzyme revealed a single polypeptide of around 38,000 molecular weight. Biophysical and biochemical analyses of the enzyme reveal unique characteristics different from those of adenosine kinases from other eukaryotic sources. The isoelectric pH of the enzyme is 8.8. In native acrylamide gels the enzyme moves with an RF of about 0.62. The enzyme displays a maximum activity at pH between 7.5 and 8.5 and is dependent upon an optimum ATP/Mg2+ ratio. ATP at high concentration inhibits the reaction. Adenosine and Mg2+ are not inhibitory. EDTA completely knocks off the activity. Enzyme activity is dependent upon the presence of active thiol group(s) at or near the active center. Under a defined set of conditions the enzyme exhibited an apparent Km for adenosine and ATP of 33 and 50 microM, respectively. Of the nucleoside triphosphates tested ATP and GTP were the most effective phosphate donors. Marginal inhibition of activity was detected with other nucleosides as competitors. However, adenosine analogs, such as 7-deaza-adenosine (tubercidin) and 6-methylmercaptopurine riboside at very low concentrations, were found to be excellent inhibitors and substrates as well. S-Adenosylhomocysteine does not inhibit the reaction even at very high concentration.     

Prospective bioremediation of toxic heavy metals in water by surfactant exopolysaccharide of Ochrobactrum pseudintermedium using cost-effective substrate

International Microbiology - Globally, the underlying peril of cumulative toxicity of heavy metals in water bodies contaminated by industrial effluents is a matter of great concern to the...     

A possible explanation of the low-level brightness–contrast illusions in the light of an extended classical receptive field model of retinal ganglion cells

The low-level brightness–contrast illusions constitute a special class within visual illusions. Speculations exist that these illusions may be processed through the filtering action of the retinal ganglion cells without necessitating much intervention from higher order processes of visual perception. Concept of the classical receptive field of the ganglion cell, derived from early physiological studies, prompted the idea that a Difference of Gaussian (DoG) model might explain the low-level illusions. In spite of its many successes, the DoG model fails to explain some of these illusions. It has been shown in this paper that it is possible to simulate those illusions with a model that takes into cognizance the role of the extended classical receptive field