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Patrick J. King - One of the best experts on this subject based on the ideXlab platform.
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A tryptophan auxotroph ofHyoscyamus muticus lacking tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for tryptophan has been shown to have the following characteristics: (i) no accumulation of tryptophan from anthranilic acid; (ii) growth on added tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for tryptophan biosynthesis, including the partial reaction 2 of tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type tryptophan synthase in plants, the tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the tryptophan-synthase complex.
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A tryptophan auxotroph of Hyoscyamus muticus lacking tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for tryptophan has been shown to have the following characteristics: (i) no accumulation of tryptophan from anthranilic acid; (ii) growth on added tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for tryptophan biosynthesis, including the partial reaction 2 of tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type tryptophan synthase in plants, the tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the tryptophan-synthase complex.
Yasuyuki Yamada - One of the best experts on this subject based on the ideXlab platform.
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cdna encoding tropinone reductase ii from Hyoscyamus niger
Plant Physiology, 1993Co-Authors: K Nakajima, Takashi Hashimoto, Yasuyuki YamadaAbstract:Two stereospecific NADPH-dependent reductases, TR-I and TR-11, constitute a branching point in the biosynthesis of tropane alkaloids. TR-I catalyzes the stereospecific reduction of tropinone to tropine (Koelen and Gross, 1982), whereas TR-I1 reduces tropinone to pseudotropine (Drager et al., 1988). We previously characterized TRs that had been purified from cultured roots of Hyoscyamus niger (Hashimoto et al., 1992) and showed that the two TRs had both common and different biochemical and kinetic properties. To obtain a better understanding of the structure and evolutionary relationship of these reductases, we isolated cDNA clones coding for TR-I1 from H. niger (Table I). An intemal amino acid sequence was found in both TR-I and TR-I1 that had been purified from the cultured roots of Datura stramonium and H. niger, respectively (Nakajima et al., 1993). An oligonucleotide probe corresponding to this sequence was synthesized and used to screen the cDNA library from cultured roots of H. niger. DNA sequencing analysis revealed that a11 four of the isolated cDNA clones encoded the TR-I1 polypeptide, probably due to the low concentration of the TR-I transcript in this genus. None of the cDNA clones contained a full ORF; some lacked the amino-terminal part and others the carboxy-terminal part and the 3‘ nontranslated region. Because the nucleotide sequence of the overlapping part (0.4-0.8 kb) matched perfectly, we concluded that these clones were derived from a single gene. The combined nucleotide sequence (1049 bp) contained a 783-bp ORF coding for a polypeptide composed of 260 amino acids, and the calculated mo1 wt of 28,436 agreed well with the molecular mass for the TR-I1 subunit (29 kD) that had been purified from H. niger (Hashimoto et al., 1992). The isolated cDNA was expressed in Escherichia coli as a fusion protein to /3-galactosidase under the control of the Zac promoter. The fusion protein was induced by isopropyl-P-Dthiogalactopyranoside, and the bacterial lysate was assayed for TR activities as described elsewhere (Nakajima et al., 1993). The fusion protein catalyzed the same highly stereospecific reduction of tropinone as the TR-I1 from H. niger; pseudotropine was the sole reaction product detected. The deduced amino acid sequence of TR-I1 from H. niger is highly homologous to that from D. stramonium (Nakajima
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diamine oxidase from cultured roots of Hyoscyamus niger its function in tropane alkaloid biosynthesis
Plant Physiology, 1990Co-Authors: Takashi Hashimoto, Akira Mitani, Yasuyuki YamadaAbstract:Diamine oxidase was partially purified from cultured roots of Hyoscyamus niger L. that produce considerable amounts of tropane alkaloids, and then characterized. N-Methylated amines inhibited the activity of the enzyme more strongly than the corresponding primary amines. N-Methylputrescine was the best substrate of those studied, the respective Km values for it and for putrescine and cadaverine being 0.33, 2.85, and 6.25 millimolar. The specificity constants Vmax/Km for putrescine and cadaverine were 11 and 1% of the constant for N-methylputrescine. Marked specificity for the N-methylated diamine would enable the Hyoscyamus enzyme to function specifically in tropane alkaloid biosynthesis.
Heinz Fankhauser - One of the best experts on this subject based on the ideXlab platform.
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A tryptophan auxotroph ofHyoscyamus muticus lacking tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for tryptophan has been shown to have the following characteristics: (i) no accumulation of tryptophan from anthranilic acid; (ii) growth on added tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for tryptophan biosynthesis, including the partial reaction 2 of tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type tryptophan synthase in plants, the tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the tryptophan-synthase complex.
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A tryptophan auxotroph of Hyoscyamus muticus lacking tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for tryptophan has been shown to have the following characteristics: (i) no accumulation of tryptophan from anthranilic acid; (ii) growth on added tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for tryptophan biosynthesis, including the partial reaction 2 of tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type tryptophan synthase in plants, the tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the tryptophan-synthase complex.
François Pythoud - One of the best experts on this subject based on the ideXlab platform.
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A tryptophan auxotroph ofHyoscyamus muticus lacking tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for tryptophan has been shown to have the following characteristics: (i) no accumulation of tryptophan from anthranilic acid; (ii) growth on added tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for tryptophan biosynthesis, including the partial reaction 2 of tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type tryptophan synthase in plants, the tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the tryptophan-synthase complex.
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A tryptophan auxotroph of Hyoscyamus muticus lacking tryptophan-synthase activity
Planta, 1990Co-Authors: Heinz Fankhauser, François Pythoud, Patrick J. KingAbstract:A variant clone of Hyoscyamus muticus (VIIIB9) with a specific, stable requirement for tryptophan has been shown to have the following characteristics: (i) no accumulation of tryptophan from anthranilic acid; (ii) growth on added tryptophan or indole but not on anthranilic acid; (iii) accumulation of indole-3-glycerol phosphate and other indole derivatives; (iv) extractable activity of the enzymes for tryptophan biosynthesis, including the partial reaction 2 of tryptophan synthase but not reactions 1 or 3. Thus these data provide in-vivo evidence for the existence of a two-component, bacterial-type tryptophan synthase in plants, the tryptophan auxotrophy of VIIIB9 probably being the consequence of a mutation in the α-subunit of the tryptophan-synthase complex.
Kirsi-marja Oksman-caldentey - One of the best experts on this subject based on the ideXlab platform.
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Transgenic Hyoscyamus muticus (Egyptian henbane)
Transgenic Crops III, 2020Co-Authors: N. Sevón, Stefania Biondi, Nello Bagni, Kirsi-marja Oksman-caldenteyAbstract:The results presented in this chapter are mostly based on our own work with Hyoscyamus muticus carried out during the years 1982–1998 in our laboratories in Finland and Italy.
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Enhanced secretion of tropane alkaloids in Nicotiana tabacum hairy roots expressing heterologous hyoscyamine-6β-hydroxylase
Journal of Experimental Botany, 2005Co-Authors: Suvi T. Häkkinen, M. Teresa Piñol, Javier Palazon, R. M. Cusido, Elisabeth Moyano, Kirsi-marja Oksman-caldenteyAbstract:Hyoscyamine-6beta-hydroxylase (H6H; EC 1.14.11.11) catalyses oxidative reactions in the biosynthetic pathway leading from hyoscyamine to the more pharmaceutically valuable tropane alkaloid scopolamine. The h6h gene encoding H6H from Hyoscyamus niger was introduced, under the control of the CaMV 35S promoter, into non-hyoscyamine-producing Nicotiana tabacum and hyoscyamine-producing Hyoscyamus muticus. The transformation was performed using a binary vector system based on Agrobacterium rhizogenes. Production of scopolamine in hairy roots was clearly correlated with the 35S-h6h transcript expression. The engineered N. tabacum and H. muticus hairy roots were studied for the production of scopolamine and other tropane and nicotine alkaloids after feeding the cultures with exogenous hyoscyamine. N. tabacum hairy roots carrying the 35S-h6h transgene showed a more efficient uptake of hyoscyamine from the culture medium and a higher rate of bioconversion of hyoscyamine to scopolamine than those of H. muticus. In particular, the secretion of scopolamine in N. tabacum hairy roots was remarkably high, up to 85% of the total scopolamine being released to the culture medium. Exogenous hyoscyamine also caused changes in nicotine alkaloid accumulation in N. tabacum hairy roots.