piperitenone and isopiperitenol

Studying the biosynthesis of oil compounds in Perilla will help to elucidate regulatory systems for secondary metabolites and reaction mechanisms for natural product synthesis. In this study, two types of alcohol dehydrogenases, isopiperitenol dehydrogenases 1 and 2 (ISPD1 and ISPD2), which are thought to participate the oxidation of isopiperitenol in the biosynthesis of perilla, were isolated from three pure lines of perilla. Both ISPD1 and ISPD2 oxidized isopiperitenol into isopiperitenone with an oxidized form of nicotinamide adenine dinucleotide (NAD(+)) cofactor. ISPD1 used both isopiperitenol diastereomers, whereas ISPD2 used cis-isomer as a substrate. However, only ISPD2 was isolated from piperitenone-type perilla. These results suggests that in perilla, ISPD2 is related to the biosynthesis of piperitenone, which was formed via (-)-cis-isopiperitenol.

Topics: Alcohol Oxidoreductases; Amino Acid Sequence; Biosynthetic Pathways; Cloning, Molecular; Molecular Sequence Data; Monoterpenes; NAD; NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases; Oils, Volatile; Perilla; Terpenes

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 a 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.

Topics: Alcohol Oxidoreductases; Carbon-Carbon Double Bond Isomerases; Chemical Phenomena; Chemistry; Chromatography, Gel; Gas Chromatography-Mass Spectrometry; Hydrogen-Ion Concentration; Isomerases; Isomerism; Monoterpenes; NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases; Oxidation-Reduction; Plants, Medicinal; Solubility; Stereoisomerism; Terpenes