Biosynthesis and Metabolism of the Tropane Alkaloids

Leete, Edward

doi:10.1055/s-0028-1097249

Cited by 92 publications

(44 citation statements)

References 16 publications

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“…Retention of "O during the in vivo conversion of Hyos-OH to scopolamine argues against the proposed biosynthetic pathway of scopolamine (17,19) in which De-hyos is a precursor of scopolamine (scheme I in Fig. 1).…”

Section: Methodsmentioning

confidence: 99%

Epoxidation in Vivo of Hyoscyamine to Scopolamine Does Not Involve a Dehydration Step

Hashimoto

Kohno²,

Yamada³

1987

Plant Physiol.

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Hyoscyamine is epoxidized to scopolamine via 6,6-hydroxyhyoscyamine in several solanaceous plants. 6,7-Dehydrohyoscyamine has been proposed to be an intermediate in the conversion of 6#-hydroxyhyoscyamine to scopolamine on the basis of the observation that this unsaturated alkaloid is converted to scopolamine when fed to a Datura scion. To determine whether a dehydration step is involved in scopolamine biosynthesis, 16-'8016j0-hydroxyhyoscyamine was prepared from I-hyoscyamine and '02 using hyoscyamine 6f6-hydroxylase obtained from root cultures of Hyoscyamus niger L. When 16-'8016,-hydroxyhyoscyamine was fed to shoot cultures of Duboisia myoporoides R. BR., the labeled alkaloid was converted to scopolamine which retained "O in the epoxide oxygen. It is concluded that 6,6-hydroxyhyoscyamine is converted in vivo to scopolamine without a dehydration step.Scopolamine, the epoxide of hyoscyamine, is one of the major alkaloids which accumulate in the family Solanaceae (7). The formation of the epoxide bridge in scopolamine begins with the hydroxylation of L-hyoscyamine to Hyos-OH' by a 2-oxoglutarate-dependent dioxygenase, hyoscyamine 6#-hydroxylase (12 De-hyos (scheme 1 in Fig. 1); '"0 should be retained if dehydration is not involved (scheme 2 in Fig. 1). MATERIALS AND METHODSChemicals. '"02 (>99 atom %) was purchased from CEA, France. L-Hyoscyamine hydrobromide and scopolamine hydrobromide were obtained from Nakarai Chemicals, Kyoto. Hyos-OH hydrobromide was prepared using hyoscyamine 6#-hydroxylase from root cultures of Hyoscyamus niger L. (12). De-hyos was synthesized by the method of Sharpless et al. (23). Other chemicals were obtained as described previously (12).Root and Shoot Cultures. Culture conditions for root cultures ofH. niger L. have been reported elesewhere (12). Shoot cultures ofDuboisia myoporoides R. BR. were initiated according to Endo et al. (6) and were subcultured on a Gyrotory shaker (model G 10-21, New Brunswick Scientific, Edison, NJ) at 100 rpm and 25°C under light (2,700-4,500 lux) in 100-ml flasks containing 25 ml of liquid B5 medium (10) supplemented with 3% (w/v) sucrose and 10 Mm 6-BA. In the feeding experiments, alkaloid solutions were neutralized with HCI when necessary and were sterilized by passing through 0.22 Am membrane filters. These were added to 10 ml ofthe above culture medium in 50-ml flasks to a final concentration of0.2 mm. The shoot cultures containing young leaves were inoculated in each flask and cultured under the above conditions.Partial Purification of Hyoscyamine 6,8-Hydroxylase. Hyoscyamine 6t3-hydroxylase was partially purified from root cultures ofH. niger. The hydroxylase in the crude extract was precipitated between 60 and 80% saturation of (NH4)2SO4 and subsequently chromatographed on a DEAE-Toyopearl 650M column. The detailed purification procedure has been reported (13). The partially purified enzyme preparation (about 23-fold in specific activity) was concentrated using Amicon

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Section: Methodsmentioning

confidence: 99%

Epoxidation in Vivo of Hyoscyamine to Scopolamine Does Not Involve a Dehydration Step

Hashimoto

Kohno²,

Yamada³

1987

Plant Physiol.

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“…Sesquiterpenes and tropane alkaloids share a common precursor, acetoacetate, which is used in the formation of both the tropine ring of hyoscyamine (Leete, 1979), and in the synthesis of the isoprenoid unit of the sesquiterpenes (Cane, 1981). Our system can thus be used to study the regulation of precursor flow in both constitutive and inducible pathways.…”

Section: Dlscusslonmentioning

confidence: 99%

“…1). Putrescine is the precursor for the tropine ring (Leete, 1979), and Phe is used in the biosynthesis of the aromatic moiety of the alkaloid. It has been previously accepted that hyoscyamine derives from the esterification of tropine with tropic acid.…”

mentioning

confidence: 99%

Selection for Hyoscyamine and Cinnamoyl Putrescine Overproduction in Cell and Root Cultures of Hyoscyamus muticus

Medina-Bolívar

Flores

1995

Plant Physiol.

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Hairy root cultures of Hyoscyamus muticus have been shown to produce stable levels of tropane alkaloids comparable to those found i n whole plants. I n contrast, cell cultures of this and other solanaceous species produce only trace amounts of alkaloids but can be used for selection of metabolic variants. We have taken advantage of both systems and the ability t o convert between them in vitro in an effort to select for increased production of the tropane alkaloid hyoscyamine. Hairy roots were converted into cell suspensions by addition of 1 mg/L 2,4-dichlorophenoxyacetic acid t o Murashige-Skoog medium (T. Murashige and F. Skoog [1962] Physiol Plant 15: 473-497) and screened for resistance t o the amino acid analog pfluorophenylalanine (PFP). Cells that could grow in media containing 400 PM PFP were selected and cloned from single cells. The resistant cells accumulated high levels of cinnamoyl putrescines, which share the same biosynthetic precursors as hyoscyamine. Hairy root cultures were regenerated from both PFPsensitive and PFP-resistant cells by removing 2,4-dichlorophenoxyacetic acid from the medium. Resistance t o PFP continued to be expressed in regenerated roots. Higher levels of hyoscyamine were found i n hairy roots regenerated from PFP-resistant cells than were found in controls. We suggest that the precursors overproduced by the PFP-resistant cells can be diverted into the hyoscyamine pathway upon the regeneration of root cultures..

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“…2 et 3) La meme evolution des teneurs en alcalo'ides est observee dans les plantes recoltees en juin et juillet, avec cependant des valeurs plus elevees. (Cosson, 1976;Leete, 1979 …”

Section: -Techniques D'analyseunclassified

Etude de la teneur en hyoscyamine et scopolamine d'une population sauvage deDatura stramoniumL. en Algérie

Houmani

Cosson

Corbineau³

et al. 1994

Acta Botanica Gallica

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Biosynthesis and Metabolism of the Tropane Alkaloids

Cited by 92 publications

References 16 publications

Epoxidation in Vivo of Hyoscyamine to Scopolamine Does Not Involve a Dehydration Step

Epoxidation in Vivo of Hyoscyamine to Scopolamine Does Not Involve a Dehydration Step

Selection for Hyoscyamine and Cinnamoyl Putrescine Overproduction in Cell and Root Cultures of Hyoscyamus muticus

Etude de la teneur en hyoscyamine et scopolamine d'une population sauvage deDatura stramoniumL. en Algérie

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