Regulation in tobacco callus of enzyme activities of the nicotine pathway |
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Authors: | R Wagner F Feth K G Wagner |
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Institution: | (1) Arbeitsgruppe Enzymologie, Gesellschaft für Biotechnologische Forschung, Mascheroder Weg 1, D-3300 Braunschweig, Federal Republic of Germany |
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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.Abbreviations HPLC
high-performance liquid chromatography
- NAD-PPase
NAD-pyrophosphatase
- NaMN-ATase
nicotinic-acid mononucleotide (NaMN) adenylyltransferase
- NaMN-GHase
NaMN-glycohydrolase
- Na-PRTase
nicotinic-acid phosphoribosyltransferase
- NMN-ATase
nicotinamide mononucleotide (NMN) adenylyltransferase
- NMN-Ghase
NMN-glycohydrolase
- PMT
putrescine methyltransferase
- Qa-PRTase
quinolinic acid phosphoribosyltransferase |
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Keywords: | Callus culture (nicotine pathway) Nicotiana (nicotine pathway) Nicotine biosynthesis Pyridine nucleotide cycle Pyridine nucleotide glycohydrolase Quinolinic acid phosphoribosyltransferase |
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