geranyl-pyrophosphate and perillaldehyde

Perilla produces the cyclohexanoid monoterpene perillaldehyde as a major constituent of an essential oil that is accumulated in its glandular trichomes. Perillaldehyde is a marker compound for quality control of soyo and has biological activities such as antibacterial, sedative, or vasodilatory effects. The predicted perillaldehyde formation involves the cyclization of geranyl diphosphate, hydroxylation, and oxidation, and cytochrome P450 plays a crucial role in perillaldehyde biosynthesis. In this study, a cytochrome P450-type enzyme with perillyl alcohol and perillaldehyde synthase activities was isolated by analyzing an expressed sequence tag library from several oil types of pure lines of perilla. A recombinant protein with a sequence that was highly specific for the type of perillaldehyde was expressed in Saccharomyces cerevisiae and evaluated by an in vitro enzymatic reaction. The recombinant protein catalyzed the hydroxylation and oxidation of limonene to perillyl alcohol and perillaldehyde. Cytochrome P450 limonene-7-hydroxylase cDNA from Perilla frutescens has been previously isolated. The cytochrome P450 isolated in this study shares 37% amino-acid identity with the previously isolated enzyme; however, it may have different characteristics.

Topics: Cloning, Molecular; Cyclohexenes; Cytochrome P-450 Enzyme System; Diphosphates; Diterpenes; Gene Library; Limonene; Monoterpenes; Oils, Volatile; Perilla frutescens; Recombinant Proteins; Terpenes

Studies on the biosynthesis of oil compounds in Perilla will help in understanding regulatory systems of secondary metabolites and in elucidating reaction mechanisms for natural product synthesis. In this study, two types of alcohol dehydrogenases, an aldo-keto reductase (AKR) and a geraniol dehydrogenase (GeDH), which are thought to participate in the biosynthesis of perilla essential oil components, such as citral and perillaldehyde, were isolated from three pure lines of perilla. These enzymes shared high amino acid sequence identity within the genus Perilla, and were expressed regardless of oil type. The overall reaction from geranyl diphosphate to citral was performed in vitro using geraniol synthase and GeDH to form a large proportion of citral and relatively little geraniol as reaction products. The biosynthetic pathway from geranyl diphosphate to citral, the main compound of citral-type perilla essential oil, was established in this study.

Topics: Acyclic Monoterpenes; Alcohol Dehydrogenase; Aldehyde Reductase; Aldo-Keto Reductases; alpha-Linolenic Acid; Amino Acid Sequence; Biosynthetic Pathways; Cloning, Molecular; Diphosphates; Diterpenes; Gene Expression; Gene Library; Kinetics; Molecular Sequence Data; Monoterpenes; Oils, Volatile; Perilla; Plant Leaves; Plant Oils; Recombinant Fusion Proteins; Sequence Alignment; Sequence Analysis, DNA; Terpenes