This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Phenylpropanoid Derivatives Biosynthesis → Stilbenes Biosynthesis|
|Biosynthesis → Secondary Metabolites Biosynthesis → Phytoalexins Biosynthesis → Stilbene Phytoalexins Biosynthesis|
Expected Taxonomic Range: Euphyllophyta
Pinosylvin (3,5-dihydroxystilbene) is found predominantly as a constituent in the heartwood of trees but is also formed in response to biotic stress in young tree seedlings, thus considered as a phytoalexin. Unlike other related hydroxystilbenes such as resveratrol ( resveratrol biosynthesis) pinosylvin lacks a hydroxyl group in ring B and originates by condensation of 3 malonyl-CoA and cinnamoyl-CoA instead of p-coumaroyl-CoA [PreisigMuller99].
Beside pinosylvin (PS), pinosylvin monomethylether (PSM) is another major stilbene that has been found in heartwood of trees being considered as constitutive protectant preventing the decay of wood by microorganisms [Hart81] [Kindl85]. Both compounds are rapidly induced upon biotic stress, e.g. caused by the fungus Botrytis cinerea the pathogen of the gray-mold rot [Schwekendiek92] or abiotic stress such as exposure to ozone [Chiron00] or UV [Gehlert90]. It has been demonstrated that pinosylvin and its monomethylether is much more effective to prevent the growth of most wood-rotting fungi than the also tested resveratrol [Seppanen04].
The enzyme, stilbene synthase (STS), catalyzing the formation of pinosylvin belongs to the plant specific polyketide synthases (PKS) and is closely related to the chalcone synthase(s) (CHS) [Lanz91] [Tropf94]. Stilbene synthases (STS) are homodimeric, plant-specific polyketide synthases occurring in widely unrelated plants. Stilbene synthases function as unimodular PKS's with a single active site and each subunit of the protein is able to synthesize the end products but with lower efficiency and product specificity [Tropf95] [Kodan02].
Stilbene synthases have been found to represent a small multigene family in plants where the several members are differentially expressed in response to exogenous stimuli. This applies even to the most primitive vascular plant, i.e. Psilotum nudum [Yamazaki01] which contain a family of four CHS/STS synthases. The most receptive element to stress seems to correspond to only one sort of stilbene synthase [Schwekendiek92] [PreisigMuller99] in pine seedlings indicating a functional ranking among the STS's responsible for pinosylvin formation in heartwood and upon stress.
About This Pathway
The stilbene synthase specific for the catalyzation of pinosylvin not only accepts cinnamoyl-CoA but also its dihydro-isomer phenylpropionyl-CoA (dihydrocinnamoyl-CoA) forming dihydropinosylvin. However, this kind of reaction does not require a different enzyme (dihydropinosylvin synthase) as previously thought [Fliegmann92] but merely reflects the broader substrate acceptance of the pinosylvin-forming stilbene synthases [Schanz92] where some members of this family express a higher affinity towards phenylpropionyl-CoA than others. The product specificity and enzyme activity of different STS's can be influenced by a single amino acid exchange in the protein sequence [Raiber95].
The other enzyme of the pathway, pinosylvin methyltransferase (PMT) has been purified and sequenced [Chiron98]. The PMT like the STS is induced in the sapwood, phloem, and needles of conifers as a response to wounding, fungal attack [Chiron00] or chemical stress such as ozone or sulphur dioxide [Rosemann91] with pinosylvin and pinosylvin monomethylester accumulating in those tissues. The experimental data so far indicate a transcriptional induction of ozone-induced stilbene biosynthesis where the sequence of polyketide synthesis (pinosylvin) and O-methylation (pinosylvin monomethylether) is triggered upon stress [Chiron00a]. As for the STS's the pinosylvin methyltransferase (PMS) represents a small multigene family in pine species where various members might be differentially regulated upon environmental signals [Chiron00].
Chiron00: Chiron H, Drouet A, Lieutier F, Payer HD, Ernst D, Sandermann H (2000). "Gene induction of stilbene biosynthesis in Scots pine in response to ozone treatment, wounding, and fungal infection." Plant Physiol 124(2);865-72. PMID: 11027734
Chiron00a: Chiron H, Drouet A, Claudot AC, Eckerskorn C, Trost M, Heller W, Ernst D, Sandermann H (2000). "Molecular cloning and functional expression of a stress-induced multifunctional O-methyltransferase with pinosylvin methyltransferase activity from Scots pine (Pinus sylvestris L.)." Plant Mol Biol 44(6);733-45. PMID: 11202436
Fliegmann92: Fliegmann J, Schroder G, Schanz S, Britsch L, Schroder J (1992). "Molecular analysis of chalcone and dihydropinosylvin synthase from Scots pine (Pinus sylvestris), and differential regulation of these and related enzyme activities in stressed plants." Plant Mol Biol 18(3);489-503. PMID: 1536925
Gehlert90: Gehlert R, Schoppner A, Kindl H (1990). "Stilbene synthase from seedlings of Pinus sylvestris: Purification and induction in response to fungal infection." Molecular Plant-Microbe Interactions, 3(6), 444-449.
Kindl85: Kindl H (1985). "Biosynthesis of stilbenes." In: Higuchi T (ed) Biosynthesis and biodegradation of wood components, Academic Press, Inc., Orlando, San Diego, New York, London, Toronto, Montreal, Sydney, Tokyo, 349-377.
Kodan02: Kodan A, Kuroda H, Sakai F (2002). "A stilbene synthase from Japanese red pine (Pinus densiflora): implications for phytoalexin accumulation and down-regulation of flavonoid biosynthesis." Proc Natl Acad Sci U S A 99(5);3335-9. PMID: 11880657
Lanz91: Lanz T, Tropf S, Marner FJ, Schroder J, Schroder G (1991). "The role of cysteines in polyketide synthases. Site-directed mutagenesis of resveratrol and chalcone synthases, two key enzymes in different plant-specific pathways." J Biol Chem 266(15);9971-6. PMID: 2033084
PreisigMuller99: Preisig-Muller R, Schwekendiek A, Brehm I, Reif HJ, Kindl H (1999). "Characterization of a pine multigene family containing elicitor-responsive stilbene synthase genes." Plant Mol Biol 39(2);221-9. PMID: 10080690
Raiber95: Raiber S, Schroder G, Schroder J (1995). "Molecular and enzymatic characterization of two stilbene synthases from Eastern white pine (Pinus strobus). A single Arg/His difference determines the activity and the pH dependence of the enzymes." FEBS Lett 361(2-3);299-302. PMID: 7698342
Rosemann91: Rosemann D, Heller W, Sandermann Jr H (1991). "Biochemical Plant Responses to Ozone II. Induction of Stilbene Biosynthesis in Scots Pine (Pinus sylvestris L.) Seedlings." Plant Physiol. 97, 1280-1286.
Seppanen04: Seppanen SK, Syrjala L, von Weissenberg K, Teeri TH, Paajanen L, Pappinen A (2004). "Antifungal activity of stilbenes in in vitro bioassays and in transgenic Populus expressing a gene encoding pinosylvin synthase." Plant Cell Rep 22(8);584-93. PMID: 14714142
Tropf94: Tropf S, Lanz T, Rensing SA, Schroder J, Schroder G (1994). "Evidence that stilbene synthases have developed from chalcone synthases several times in the course of evolution." J Mol Evol 38(6);610-8. PMID: 8083886
Tropf95: Tropf S, Karcher B, Schroder G, Schroder J (1995). "Reaction mechanisms of homodimeric plant polyketide synthase (stilbenes and chalcone synthase). A single active site for the condensing reaction is sufficient for synthesis of stilbenes, chalcones, and 6'-deoxychalcones." J Biol Chem 270(14);7922-8. PMID: 7713888
Yamazaki01: Yamazaki Y, Suh DY, Sitthithaworn W, Ishiguro K, Kobayashi Y, Shibuya M, Ebizuka Y, Sankawa U (2001). "Diverse chalcone synthase superfamily enzymes from the most primitive vascular plant, Psilotum nudum." Planta 214(1);75-84. PMID: 11762173
Rubio06: Rubio S, Larson TR, Gonzalez-Guzman M, Alejandro S, Graham IA, Serrano R, Rodriguez PL (2006). "An Arabidopsis mutant impaired in coenzyme A biosynthesis is sugar dependent for seedling establishment." Plant Physiol 140(3);830-43. PMID: 16415216
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