Enhanced structural diversity in terpenoid biosynthesis: enzymes, substrates and cofactors.

The enormous diversity of terpenes found in nature is generated by enzymes known as terpene synthases, or cyclases. Some are also known for their ability to convert a single substrate into multiple products. This review comprises monoterpene and sesquiterpene synthases that are multiproduct in nature along with the regulation factors that can alter the product specificity of multiproduct terpene synthases without genetic mutations.

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.

Theoretical and experimental analysis of the reaction mechanism of MrTPS2, a triquinane-forming sesquiterpene synthase from chamomile.

Terpene synthases, as key enzymes of terpene biosynthesis, have garnered the attention of chemists and biologists for many years. Their carbocationic reaction mechanisms are responsible for the huge variety of terpene structures in nature. These mechanisms are amenable to study by using classical biochemical approaches as well as computational analysis, and in this study we combine quantum-chemical calculations and deuterium-labeling experiments to elucidate the reaction mechanism of a triquinane forming sesquiterpene synthase from chamomile.

Metabolic engineering of the C16 homoterpene TMTT in Lotus japonicus through overexpression of (E,E)-geranyllinalool synthase attracts generalist and specialist predators in different manners.

Plant defenses against herbivores include the emission of specific blends of volatiles, which enable plants to attract natural enemies of herbivores. We characterized a plastidial terpene synthase gene, PlTPS2, from lima bean (Phaseolus lunatus). The recombinant PlTPS2 protein was multifunctional, producing linalool, (E)-nerolidol and (E,E)-geranyllinalool, precursors of (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene [TMTT].

A single amino acid determines the site of deprotonation in the active center of sesquiterpene synthases SbTPS1 and SbTPS2 from Sorghum bicolor.

The multitude of terpene carbon skeletons found in nature is formed by enzymes known as terpene synthases (TPSs). These proteins are often multiproduct enzymes converting a single prenyl diphosphate substrate into a mixture of terpene products. The recently identified sesquiterpene synthases SbTPS1 and SbTPS2 from Sorghum bicolor produce terpene blends containing the same products, but in different proportions.

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.

The isogene 1-deoxy-D-xylulose 5-phosphate synthase 2 controls isoprenoid profiles, precursor pathway allocation, and density of tomato trichomes.

Plant isoprenoids are formed from precursors synthesized by the mevalonate (MVA) pathway in the cytosol or by the methyl-D-erythritol 4-phosphate (MEP) pathway in plastids. Although some exchange of precursors occurs, cytosolic sesquiterpenes are assumed to derive mainly from MVA, while plastidial monoterpenes are produced preferentially from MEP precursors. Additional complexity arises in the first step of the MEP pathway, which is typically catalyzed by two divergent 1-deoxy-D-xylulose 5-phosphate synthase isoforms (DXS1, DXS2).

Early herbivore-elicited events in terpenoid biosynthesis.

Volatile terpenoids, the major products among the herbivore-induced plant volatiles in the legume, mediate interactions that attract herbivores' natural enemies and serve as signals to neighboring plants. We recently demonstrated cross-talk among the signaling components involving Ca(2+), jasmonic acid and ethylene, which are altogether responsible for volatile terpenoid formation in Medicago truncatula. Herbivore-stimulated Ca(2+) transients are an additional element that has an impact on the composition of the blend of terpenoids, whose biosynthesis depends on the jasmonic acid/ethylene pathway.

Herbivore-induced terpenoid emission in Medicago truncatula: concerted action of jasmonate, ethylene and calcium signaling.

Plant volatiles emitted by Medicago truncatula in response to feeding larvae of Spodoptera exigua are composed of a complex blend of terpenoids. The cDNAs of three terpene synthases (TPSs), which contribute to the blend of terpenoids, were cloned from M. truncatula.