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Title: (Regulation of teopene metabolism). Progress report. [Mentha piperita]

Abstract

Progress in elucidating the biosynthesis of several monoterpenes in the peppermint is described. Tracer studies were performed to clarify metabolic pathways involved. Several growth regulators were screened for their influence on monoterpene composition and yield in peppermint and sage. (DT)

Authors:
Publication Date:
Research Org.:
Washington State Univ., Pullman (USA)
OSTI Identifier:
6292306
Report Number(s):
DOE/ER/12027-2
ON: DE86006343
DOE Contract Number:
AT06-82ER12027
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 10 SYNTHETIC FUELS; TERPENES; BIOSYNTHESIS; CATABOLISM; BIOLOGICAL PATHWAYS; CAMPHOR; FRACTIONATION; HERBS; ISOMERASES; OXIDOREDUCTASES; TRACER TECHNIQUES; TRITIUM COMPOUNDS; VEGETABLE OILS; ENZYMES; ISOTOPE APPLICATIONS; KETONES; LABELLED COMPOUNDS; METABOLISM; OILS; ORGANIC COMPOUNDS; OTHER ORGANIC COMPOUNDS; PLANTS; SEPARATION PROCESSES; SYNTHESIS; 550201* - Biochemistry- Tracer Techniques; 090120 - Hydrocarbon Fuels- Preparation- (1976-1989)

Citation Formats

Croteau, R. (Regulation of teopene metabolism). Progress report. [Mentha piperita]. United States: N. p., 1985. Web.
Croteau, R. (Regulation of teopene metabolism). Progress report. [Mentha piperita]. United States.
Croteau, R. 1985. "(Regulation of teopene metabolism). Progress report. [Mentha piperita]". United States. doi:.
@article{osti_6292306,
title = {(Regulation of teopene metabolism). Progress report. [Mentha piperita]},
author = {Croteau, R.},
abstractNote = {Progress in elucidating the biosynthesis of several monoterpenes in the peppermint is described. Tracer studies were performed to clarify metabolic pathways involved. Several growth regulators were screened for their influence on monoterpene composition and yield in peppermint and sage. (DT)},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1985,
month = 1
}

Technical Report:
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  • Studies on the regulation of monoterpene metabolism in M. piperita were conducted. All of the steps from the acyclic precursor geranyl pyrophosphate to the various menthol isomers have been demonstrated. The first intermediate to accumulate in vivo is d-pulegone. The emphasis has been on the demonstration, partial purification and characterization of the relevant enzymes in the pathway. The studies on the isopiperitenol dehydrogenase and isopiperitenone isomerase have been completed. We are not studying the endocyclic double-bond reductase (NADPH-dependent) and, based on substrate specificity studies and the previously demonstrated isomerization of cis- isopulegone to pulegone, are now virtually convinced that themore » major pathway to menthol(s) in peppermint involves reduction of isopiperitenone to isopulegone and isomerication of isopulegone to pulegone. 16 refs., 1 fig.« less
  • Progress in understanding of the metabolism of monoterpenes by peppermint and spearmint is recorded including the actions of two key enzymes, geranyl pyrophosphate:limonene cyclase and a UDP-glucose dependent glucosyl transferase; concerning the ultrastructure of oil gland senescence; enzyme subcellular localization; regulation of metabolism; and tissue culture systems.
  • Previous studies have shown that the monoterpene ketone l-(G-/sup 3/H)-menthone is reduced to the epimeric alcohols l-menthol and d-neomenthol in leaf discs of flowering peppermint (Mentha piperita L.), and that a portion of the menthol is converted to menthyl acetate while the bulk of the neomenthol is transformed to neomenthyl-..beta..-D-glucoside. When l-(3-/sup 3/H)menthol and d-(3-/sup 3/H)neomenthol are separately administered to leaf discs, both menthyl and neomenthyl acetates and menthyl and neomenthyl glucosides are formed with nearly equal facility, suggesting that the metabolic specificity observed with the ketone precursor was not a function of the specificity of the transglucosylase or transacetylasemore » but rather a result of compartmentation of each stereospecific dehydrogenase with the appropriate transferase. Co-purification of the acceptor-mediated activities, and differential activation and inhibition studies, provided strong evidence that the same UDP-glucose-dependent enzyme could transfer glucose to either l-menthol or d-neometnthol. These results demonstrate that the specific in vivo conversion of l-menthone to l-menthyl acetate and d-neomenthyl-..beta..-D-glucoside cannot be attributed to the selectivity of the transferases, and they clearly indicate that the metabolic specificity observed is a result of compartmentation effects.« less
  • Previous studies have shown that the monoterpene ketone l-(G-/sup 3/H) menthone is reduced to the epimeric alcohols l-menthol and d-neomenthol in leaves of flowering peppermint (Mentha piperita L.), and that a portion of the menthol is converted to methyl acetate while the bulk of the neomenthol is transformed to neomenthyl-..beta..-D-glucoside which is then transported to the rhizome. Analysis of the disposition of l-(G)/sup 3/H)menthone applied to midstem leaves of intact flowering plants allowed the kinetics of synthesis and transport of the monoterpenyl glucoside to be determined, and gave strong indication that the glucoside was subsequently metabolized in the rhizome. Studiesmore » with d-(G-/sup 3/H)neomenthyl-..beta..-D-glucoside as substrate, using excised rhizomes or rhizome segments, confirmed the hydrolysis of the glucoside as an early step in metabolism at this site, and revealed that the terpenoid moiety was further converted to a series of ether-soluble, methanol-soluble, and water-soluble products. The conversion of menthone to the lactone, and of the lactone to more polar products, were confirmed in vivo using l-(G-/sup 3/H)menthone and l-(G-/sup 3/H)-3,4-menthone lactone as substrates. Additional oxidation products were formed in vivo via the desaturation of labeled neomenthol and/or menthone, but none of these transformations appeared to lead to ring opening of the p-menthane skeleton. Each step in the main reaction sequence, from hydrolysis of neomenthyl glucoside to lactonization of menthone, was demonstrated in cell-free extracts from the rhizomes of flowering mint plants. The lactomization step is of particular significance in providing a means of cleaving the p-methane ring to afford an acyclic carbon skeleton that can be further degraded by modifications of the well-known ..beta..-oxidation sequence. 41 references, 3 figures, 1 table.« less
  • Soluble enzyme extracts from peppermint leaves, when treated with polystyrene resin to remove endogenous monoterpenes and assayed with unlabeled substrates coupled with capillary gas-liquid chromatographic/mass spectrometric detection methods, were shown to oxidize isopiperitenol to isopiperitenone, and to isomerize isopiperitenone to piperitenone. The enzymes responsible for the monoterpenol dehydrogenation and the subsequent allylic isomerization were separated and partially purified by chromatography on Sephadex G-150, and were shown to have molecular weights of approximately 66,000 and 54,000, respectively. The general properties of the NAD-dependent dehydrogenase were examined, and specificity studies indicated that a double bond adjacent to the carbinol carbon was amore » required structural feature of the monoterpenol substrate. General properties of the isomerase were also determined, and it was demonstrated that the double bond migration catalyzed by this enzyme involved an intramolecular 1,3-hydrogen transfer. These enzymatic transformations represent two key steps in the metabolic pathway for the conversion of the initially formed cyclic olefin, (+/-)-limonene, to (-)-menthol and related monoterpenes characteristic of peppermint. Some stereochemical features of these reactions, and of the overall biogenetic scheme, are described. 39 references, 5 figures.« less