Stilbene synthases

Chalcone Synthase / Stilbene Synthase Family of Plant Polyketide Synthases. 199... 

Recently, a new polyketide biosynthetic pathway in bacteria that parallels the well studied plant PKSs has been discovered that can assemble small aromatic metabolites.8,9 These type III PKSs10 are members of the chalcone synthase (CHS) and stilbene synthase (STS) family of PKSs previously thought to be restricted to plants.11 The best studied type III PKS is CHS. Physiologically, CHS catalyzes the biosynthesis of 4,2, 4, 6 -tetrahydroxychalcone (chalcone). Moreover, in some organisms CHS works in concert with chalcone reductase (CHR) to produce 4,2 ,4 -trihydroxychalcone (deoxychalcone) (Fig. 12.1). Both natural products constitute plant secondary metabolites that are used as precursors for the biosynthesis of anthocyanin pigments, anti-microbial phytoalexins, and chemical inducers of Rhizobium nodulation genes.12... 

In this chapter, we describe the atomic resolution structural elucidation of several plant type III polyketide synthases, including chalcone synthase, 2-pyrone synthase, and stilbene synthase. Manipulation of the catalytic activity and specificity of these biosynthetic enzymes by using a structurally guided approach offers a novel... 

CHALCONE SYNTHASE / STILBENE SYNTHASE FAMILY OF PLANT POLYKETIDE SYNTHASES... 

To resolve the issue of cyclization specificity, the x-ray crystal structure of the stilbene synthase from pine was determined to atomic resolution. This information allowed the mutagenic conversion of alfalfa CHS to a functional STS, and crystal structures of this engineered STS were solved, in the apo form and with resveratrol bound in the active site (Austin and Noel, unpublished). These experiments support a mechanistic proposal, which prompted further mutagenic and modeling experiments. This work has allowed the elucidation of the structural and mechanistic basis for cyclization specificity (aldol versus Claisen condensation) in the CHS family of type III PKSs. 

SCHRODER, J., The chalcone/stilbene synthase-type family of condensing enzymes. In Comprehensive Natural Products Chemistry, vol. 1, Polyketides and Other Secondary Metabolites Including Fatty Acids and Their Derivatives (U. Sankawa ed.), Elsevier, Amersterdam, 1999, pp. 749-771. 

TROPF, S LANZ, T., RENSING, S.A., SCHRODER, J., SCHRODER, G., Evidence that stilbene synthases have developed from chalcone synthases several times in the course of evolution, J. Mol. Evol., 1994,38, 610-618. 

ZUURBIER, K.W.M., LESER, J., BERGER, T., HOFTE, A.J.P., SCHRODER, G., VERPOORTE, R., SCHRODER, J., Hydroxy-2-pyrone formation by chalcone and stilbene synthase with nonphysiological substrates, Phytochemistry, 1998,49, 1945-1951. 

SUH, D.-Y., FUKUMA, K., KAGAMI, J., YAMAZAKI, Y., SHIBUYA, M., EBIZUKA, Y., SANKAWA, U., Identification of amino acid residues important in the cyclization reactions of chalcone and stilbene synthases, Biochem. J., 2000,350, 229-235. 

PKSs are characterized by their ability to catalyze the formation of polyketide chains from the sequential condensation of acetate units from malonate thioesters. In plants they produce a range of natural products with varied in vivo and pharmacological properties. PKSs of particular note include acridone synthase, bibenzyl synthase, 2-pyrone synthase, and stilbene synthase (STS). STS forms resveratrol, a plant defense compound of much interest with regard to human health. STS shares high sequence identity with CHS, and is considered to have evolved from CHS more than once. ° Knowledge of the molecular structure of the CHS-like enzymes has allowed direct engineering of CHS and STS to alter their catalytic activities, including the number of condensations carried out (reviewed in Refs. 46, 51, 52). These reviews also present extensive, and superbly illustrated, discussions of CHS enzyme structure and reaction mechanism. 

Fischer, R., Budde, L, and Hain, R., Stilbene synthase gene expression causes changes in flower colour and male sterility in tobacco. Plant J., 11, 489, 1997. 

Stilbene synthase shows similarity to chalcone synthase, which is not surprising given that stilbenes (3.97) also originate from the condensation of... 

Figure 3-15. Biosynthesis of stilbene from p-coumaroyl-CoA with three molecules malonyl-CoA, catalyzed by the enzyme stilbene synthase (a E.C. 2.3.1.95).

Figure 1.36 Schematic diagram of the stilbene and flavonoid biosynthetic pathway. Enzyme abbreviations SS, stilbene synthase CHS, chalcone synthase CHR, chalcone reductase CHI, chalcone isomerase IFS, isoflavone synthase FNS, flavone synthase F3H, flavanone 3-hydroxylase FLS, flavonol synthase F3 H, flavonoid 3 -hydroxylase DFR, dihydroflavonol 4-reductase LAR, leucoanthocyanidin 4-reductase LDOX, leucocyanidin deoxygenase ANR, anthocyanidin reductase EU, extension units TU, terminal unit.

Hain R, Bieseler B, Kindi H, Schroder G, Stocker R. 1990 Expression of a stilbene synthase gene in Nicotiana tabacum results in synthesis of the phytoalexin resveratrol. Plant Mol Biol 15 325-335. 

Morelli R, Das S, Bertelli A, Bollini R, Scalzo RL, Das DK, Falchi M. 2006. The introduction of the stilbene synthase gene enhances the natural antiradical activity of Lycopersicon esculentum mill. Mol Cell Biochem 282 65-73. 

Schoeppner A, Kindi H. 1979. Stilbene synthase (pinosylvine synthase) and its induction by ultraviolet light. FEBS Lett 108 349-352. 

Kodan A, Kuroda H, Sakai F. 2002. Stilbene synthase from Japanese red pine (Pinus densiflora) implications for phytoalexin accumulation and down-regulation of flavonoid biosynthesis. Proc Natl Acad Sci USA 99 3335-3339. 

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 361 299-302. 

Versari A, Parpinello GP, Tronielli GB, Ferrarini R, Giulivo C. 2001 Stilbene compounds and stilbene synthase expression during ripening, wilting and UV treatment in grape cv. Corvina. J Agric Food Chem 49 5531-5536. 

Fig. 1 Biosynthesis of plant polyphenols by CHS-superfamily type III PKSs. CHS chalcone synthase STS stilbene synthase ACS acridone synthase VPS valerophenone synthase SPS styrylpyrone synthase BPS benzophenone synthase OAS olivetolic acid synthase 2PS 2-pyrone synthase BAS benzalacetone synthase CUS curcumin synthase...

Schroder J (1999) The chalcone/stilbene-synthase family of condensing enzymes. In Sankawa U (ed) Comprehensive natural products chemistry, vol 1. Pergamon, Oxford, pp 749-771... 

Austin MB, Bowman ME, Ferrer J-L, Schroder J, Noel JP (2004) An aldol switch discovered in stilbene synthases mediates cyclization specificity of Type III polyketide synthases. Chem Biol 11 1179-1194... 

Shomura Y, Torayama I, Suh DY, Xiang T, Kita A, Sankawa U, Miki K (2005) Crystal structure of stilbene synthase from Arachis hypogaea. Proteins 60 803-806... 

Tropf S, Karcher B, Schroder G, Schroder J (1995) Reaction mechanisms of homodimeric plant polyketide syntahses (stilbene synthase and chalcone synthase). J Biol Chem 270 7922-7928... 

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