- Alternate Cyclization Cascade Initiated by Substrate Isomer in Multiproduct Terpene Synthase from Medicago truncatula
-
Promiscuity of terpene synthases results in the enormous diversity of terpenes found in nature. Multiproduct sesquiterpene synthase MtTPS5 isolated from Medicago truncatula generates 27 optically pure products from its natural substrate (2E,6E)-farnesyl diphosphate (FDP). In order to study the promiscuity of MtTPS5, (2Z,6E)-FDP, an analogue of presumptive reaction intermediates from natural reaction cascade, was utilized as a substrate. This stereoisomer induced a novel cyclization pathway leading to sesquiterpenes based on humulane, amorphene, and himachalane skeletons. Interestingly, none of these products matched those observed on incubation of MtTPS5 with natural (2E,6E)-FDP. Further determination of the absolute configuration of each product helped rebuild the stereochemical route of the reaction cascade. Interestingly, the presence of only one enantiomer of each product was observed, indicating the highly stereospecific nature of the enzymatic reaction. Substrate promiscuity of terpene synthases provides organism access to novel chemical bouquets of high optical purity by utilizing existing enzymes. The presence of this mechanism was indicated by the presence of these alternate products in natural herbivore-induced volatiles of M. truncatula.
- Vattekkatte, Abith,Garms, Stefan,Boland, Wilhelm
-
p. 2855 - 2861
(2017/03/23)
-
- A multiproduct terpene synthase from medicago truncatula generates cadalane sesquiterpenes via two different mechanisms
-
Terpene synthases are responsible for a large diversity of terpene carbon skeletons found in nature. The multiproduct sesquiterpene synthase MtTPS5 isolated from Medicago truncatula produces 27 products from farnesyl diphosphate (1, FDP). In this paper, we report the reaction steps involved in the formation of these products using incubation experiments with deuterium-containing substrates; we determined the absolute configuration of individual products to establish the stereochemical course of the reaction cascade and the initial conformation of the cycling substrate. Additional labeling experiments conducted with deuterium oxide showed that cadalane sesquiterpenes are mainly produced via the protonation of the neutral intermediate germacrene D (5). These findings provide an alternative route to the general accepted pathway via nerolidyl diphosphate (2, NDP) en route to sesquiterpenes with a cadalane skeleton. Mutational analysis of the enzyme demonstrated that a tyrosine residue is important for the protonation process.
- Garms, Stefan,Koellner, Tobias G.,Boland, Wilhelm
-
supporting information; experimental part
p. 5590 - 5600
(2010/11/20)
-
- The role of germacrene D as a precursor in sesquiterpene biosynthesis: Investigations of acid catalyzed, photochemically and thermally induced rearrangements
-
Germacrene D is considered as a precursor of many sesquiterpene hydrocarbons. We have investigated the acid catalyzed as well as the photochemically and thermally induced rearrangement processes of germacrene D isolated from several Solidago species, which contain both enantiomers of germacrene D. Enantiomeric mixtures of sesquiterpenes of the cadinane, eudesmane (selinane), oppositane, axane, isodaucane, and bourbonane group as well as isogermacrene D were identified as main products and made available as reference compounds for structure investigations and stereochemical assignments of plant constituents. δ-Amorphene, one of the rearrangement products, was identified as a natural product for the first time. The absolute configuration of γ-amorphene was revised by correlation with the absolute configuration of germacrene D. The mechanisms of the rearrangement reactions are discussed. (C) 2000 Elsevier Science Ltd.
- Buelow, Nils,Koenig, Wilfried A
-
p. 141 - 168
(2007/10/03)
-
- Total syntheses of (±)-α- And (±)-β-copaene and formal total syntheses of (±)-sativene, (±)-cis-sativenediol, and (±)-helminthosporal
-
Conversion of the previously reported, carvacrol-based 4(S*)-isopropyl-7(R*)-chlorobicyclo[3.1.1]heptan-6-one and its bromo equivalent into (±)-α- and (±)-β-copaene it described. Model 5-nor-β-copaene was synthesized in the following manner, (a) γ-(trimet
- Wenkert, Ernest,Bookser, Brett C.,Arrbenius, Thomas S.
-
p. 644 - 654
(2007/10/02)
-
- SESQUITERPENE ALCOHOLS OF THE COPANE SERIES FROM ESSENTIAL OIL OF OCIMUM AMERICANUM
-
The volatile oil of Ocimum americanum afforded nine monoterpene hydrocarbons, four oxygenated monoterpenes, 12 sesquiterpene hydrocarbons, 7 sesquiterpene alcohols and a few unidentified trace compounds.Four new alcohols of the uncommon copane series have also been isolated and their structures elucidated by spectroscopic methods and chemical transformations.
- Upadhyay, Ram K.,Misra, Laxmi N.,Singh, Gurdip
-
p. 691 - 693
(2007/10/02)
-