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  • 1985-1989  (4)
  • Pyridine nucleotide cycle  (3)
  • 72.20  (1)
  • Industrial Chemistry and Chemical Engineering
  • Organic Chemistry
  • 1
    Electronic Resource
    Electronic Resource
    Photopyroelectric spectroscopy (P2ES) of electronic defect centers in crystalline n-CdS (1987)
    Springer
    Applied physics 44 (1987), S. 123-130 
    Details
    ISSN: 1432-0630
    Keywords: 72.20 ; 61.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Photopyroelectric spectroscopy (P2ES) of n-CdS single crystals was performed at an open circuit, and in conjunction with photocurrent spectroscopy (PCS) in the presence of an applied ac or dc transverse field. The results showed that P2ES is very sensitive to the presence of deliberately introduced subbandgap defect structures, with the P2E signal dominated by non-radiative de-excitation mechanisms at defect centers. The potential of this technique as a powerful electronic defect diagnostic tool, combined with the overall experimental simplicity, was demonstrated with mm-thick crystals used as received in an open-cell geometry.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00626412
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    The pyridine-nucleotide cycle in tobacco Enzyme activities for the de-novo synthesis of NAD (1985)
    Springer
    Planta 165 (1985), S. 532-537 
    Details
    ISSN: 1432-2048
    Keywords: NAD-synthetase ; Nicotiana (pyridine nucleotides) ; Nicotinic acid mononucleotide adenyltransferase ; Pyridine nucleotide cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The enzyme activities of the pyridine-nucleotide cycle, which transform nicotinic acid mononucleotide (NaMN) into NAD, have been characterized. The investigations were based on the extraction of protein, its purification on disposable gel-filtration columns, and determination of the enzymatic activities by high-performance liquid chromatography techniques. The latter technique avoided the synthesis and use of radioactive precursors. The NaMN-adenylyltransferase which converts NaMN into NaAD (nicotinic acid adenine dinucleotide) and NAD-synthetase which converts NaAD into NAD were characterized by their kinetic parameters and their specific activities in different tobacco tissues. This is the first report on NAD-synthetase from tissue of a higher plant. It was found that NAD-synthetase accepted both glutamine and asparagine for the amide transfer. Adenylyltransfer also occured with nicotinamide mononucleotide (NMN) which was transformed to NAD, whereas the glutamine-dependent amidation was only observed with NaAD. Thus, an additional route for the synthesis of NAD (NaMN→NMN→NAD) obviously does not exist. A comparison of the enzyme activities in tobacco tissues with different capacities for the synthesis of nicotine showed that, in contrast to quinolinic acid phosphoribosyltransferase whose activity was strictly correlated with the nicotine content, only NaMN-adenylyltransferase showed a smooth correlation, whereas NAD-synthetase was not affected at all.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00398100
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    The pyridine-nucleotide cycle in tobacco (1986)
    Springer
    Planta 167 (1986), S. 226-232 
    Details
    ISSN: 1432-2048
    Keywords: NAD pyrophosphatase ; Nicotinamidase ; Nicotiana (pyridine-nucleotide cycle) ; Nicotine biosynthesis ; Pyridine nucleotide cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to elucidate the NAD-recycling pathway the following enzyme activities have been characterized in different tobacco tissues and in tomato root: NAD pyrophosphatase, nicotinamide mononucleotide (NMN)/nicotinic acid mononucleotide (NaMN) glycohydrolases, nicotinamidase and nicotinic acid phosphoribosyltransferase. The investigations were performed with protein extracts purified by gel filtration and enzymatic activities were determined by high-performance liquid chromatography methods. The kinetic parameters of the different enzymes from tobacco root and their specificity are reported. The data are in favor of the so-called pyridine-nucleotide cycle VI (NAD→NMN→nicotinamide→nicotinic acid→NaMN→nicotinic acid adenine dinucleotide→NAD). In the nicotine-producing tobacco root a further direct route leading from NaMN to nicotinic acid is proposed. These data are reconciled with the assumption that it is nicotinic acid which is provided by the pyridine-nucleotide cycle for the synthesis of nicotine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00391419
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation in tobacco callus of enzyme activities of the nicotine pathway (1986)
    Springer
    Planta 168 (1986), S. 408-413 
    Details
    ISSN: 1432-2048
    Keywords: Callus culture (nicotine pathway) ; Nicotiana (nicotine pathway) ; Nicotine biosynthesis ; Pyridine nucleotide cycle ; Pyridine nucleotide glycohydrolase ; Quinolinic acid phosphoribosyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In tobacco callus, the induction of nicotine synthesis, which stimulates enzyme activities of the ornithine-methylpyrroline route (see the preceding paper), also leads to marked changes in the enzyme activities of the pyridine-nucleotide cycle. This cycle provides the metabolite (probably nicotinic acid) for condensation with methylpyrroline to produce nicotine. The activities of eight enzymes of the pyridine-nucleotide cycle and of quinolinic-acid phosphoribosyltransferase, the anaplerotic enzyme, were determined by high-performance liquid chromatography assays. The distinct changes of their activities upon induction of nicotine synthesis lead to the following conclusions: i) nicotinic acid is the relevant metabolite which is provided by the pyridine-nucleotide cycle and consumed for nicotine synthesis. ii) The enhancement of the nicotinic-acid pool arises in two ways, by synthesis of NAD and degradation via nicotinamide mononucleotide and by a direct route from nicotinic-acid mononucleotide (NaMN) which is degraded by a glycohydrolase with a rather high K m value. Such a K m value prevents the complete depletion of the NaMN pool.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392369
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    Paper (German National Licenses)
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