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An Aldol Switch Discovered in Stilbene Synthases Mediates Cyclization of Specificity of Type III Polyketide Synthases: 18xCHS structure
Structural highlights
FunctionCHS2_MEDSA The primary product of this enzyme is 4,2',4',6'-tetrahydroxychalcone (also termed naringenin-chalcone or chalcone) which can under specific conditions spontaneously isomerize into naringenin.[1] [2] [3] [4] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedStilbene synthase (STS) and chalcone synthase (CHS) each catalyze the formation of a tetraketide intermediate from a CoA-tethered phenylpropanoid starter and three molecules of malonyl-CoA, but use different cyclization mechanisms to produce distinct chemical scaffolds for a variety of plant natural products. Here we present the first STS crystal structure and identify, by mutagenic conversion of alfalfa CHS into a functional stilbene synthase, the structural basis for the evolution of STS cyclization specificity in type III polyketide synthase (PKS) enzymes. Additional mutagenesis and enzymatic characterization confirms that electronic effects rather than steric factors balance competing cyclization specificities in CHS and STS. Finally, we discuss the problematic in vitro reconstitution of plant stilbenecarboxylate pathways, using insights from existing biomimetic polyketide cyclization studies to generate a novel mechanistic hypothesis to explain stilbenecarboxylate biosynthesis. An aldol switch discovered in stilbene synthases mediates cyclization specificity of type III polyketide synthases.,Austin MB, Bowman ME, Ferrer JL, Schroder J, Noel JP Chem Biol. 2004 Sep;11(9):1179-94. PMID:15380179[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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