Abstract
Terpene synthases are responsible for synthesis of a large number of terpenes in plants using substrates provided by two distinct metabolic pathways, the mevalonate-dependent pathway that is located in cytosol and has been suggested to be responsible for synthesis of sesquiterpenes (C15), and 2-C-methyl-D-erythritol-4-phosphate pathway located in plastids and suggested to be responsible for the synthesis of hemi- (C5), mono- (C10), and diterpenes (C20). Recent advances in characterization of genes and enzymes responsible for substrate and end product biosynthesis as well as efforts in metabolic engineering have demonstrated existence of a number of multi-substrate terpene synthases. This review summarizes the progress in the characterization of such multi-substrate terpene synthases and suggests that the presence of multi-substrate use might have been significantly underestimated. Multi-substrate use could lead to important changes in terpene product profiles upon substrate profile changes under perturbation of metabolism in stressed plants as well as under certain developmental stages. We therefore argue that multi-substrate use can be significant under physiological conditions and can result in complicate modifications in terpene profiles.
Highlights
Plants synthesize a vast array of secondary metabolites, many of which have been used by humans due to their medicinal, culinary, and cosmetic properties (Balandrin et al, 1985)
Our analysis suggests that multi-substrate use is more common in plants than generally thought and advocates for conduction of further systematic studies using multiple substrates across phylogenetically different plant groups harboring terpene synthases (TPSs) from different clades to gain an insight into the existence of the capacity for multi-substrate use across plant kingdom
While C5/C10 and C10/C20 multi-substrate plastidic enzymes can readily catalyze formation of multiple products because their C5, C10, and C20 substrates are available in the plastids, this review challenges the widespread consensus that presence of geranyl diphosphate (GDP) and monoterpene synthesis is confined to the plastids, and presence of farnesyl diphosphate (FDP) and sesquiterpene synthesis is confined to the cytosol
Summary
Plants synthesize a vast array of secondary metabolites, many of which have been used by humans due to their medicinal, culinary, and cosmetic properties (Balandrin et al, 1985). Analysis of the structure of bidomain, α-β, kaurene like diterpene synthase from Triticum aestivum (TaKSL5) that can use both ent-copalyl diphosphate to produce ent-kaurene and (E,E)-FDP to produce (E)-nerolidol (Hillwig et al, 2011), suggests that evolution of sesquiterpene synthesis can occur first by loss of γ-domain followed by changes in subcellular localization by loss of transit peptide and further diversification and loss of capacity for use of C20 substrate.
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