Unique animal prenyltransferase with monoterpene synthase activity
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Monoterpenes are structurally diverse natural compounds that play an essential role in the chemical ecology of a wide array of organisms. A key enzyme in monoterpene biosynthesis is geranyl diphosphate synthase (GPPS). GPPS is an isoprenyl diphosphate synthase that catalyzes a single electrophilic condensation reaction between dimethylallyl diphosphate (C5) and isopentenyl diphosphate (C5) to produce geranyl diphosphate (GDP; C10). GDP is the universal precursor to all monoterpenes. Subsequently, monoterpene synthases are responsible for the transformation of GDP to a variety of acyclic, monocyclic, and bicyclic monoterpene products. In pheromone-producing male Ips pini bark beetles (Coleoptera: Scolytidae), the acyclic monoterpene myrcene is required for the production of the major aggregation pheromone component, ipsdienol. Here, we report monoterpene synthase activity associated with GPPS of I. pini. Enzyme assays were performed on recombinant GPPS to determine the presence of monoterpene synthase activity, and the reaction products were analyzed by coupled gas chromatography–mass spectrometry. The functionally expressed recombinant enzyme produced both GDP and myrcene, making GPPS of I. pini a bifunctional enzyme. This unique insect isoprenyl diphosphate synthase possesses the functional plasticity that is characteristic of terpene biosynthetic enzymes of plants, contributing toward the current understanding of product specificity of the isoprenoid pathway.
KeywordsPheromone Mevalonate pathway Isoprenyl diphosphate Monoterpene
Supported in part by NSF grant IBN-0719279. This article represents a contribution of the Nevada Agricultural Experiment Station (publication #03087101). We thank the managers of the Whittell Forest (UNR) for allowing us to collect beetles and Jörg Bohlmann for his helpful comments. This research was conducted in accordance with the current laws of the USA. This publication was made possible by NIH Grant Number P20 RR-016464 from the INBRE Program of the National Center for Research Resources.
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