title: Distinct substrate specificities and unusual substrate flexibilities of two hydroxycinnamoyltransferases, rosmarinic acid synthase and hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyl-transferase, from Coleus blumei Benth.
abstract: cDNAs and genes encoding a hydroxycinnamoyl-CoA:hydroxyphenyllactate hydroxycinnamoyltransferase (CbRAS; rosmarinic acid synthase) and a hydroxycinnamoyl-CoA:shikimate hydroxycinnamoyltransferase (CbHST) were isolated from Coleus blumei Benth. (syn. Solenostemon scutellarioides (L.) Codd; Lamiaceae). The proteins were expressed in E. coli and the substrate specificity of both enzymes was tested. CbRAS accepted several CoA-activated phenylpropenoic acids as donor substrates and D-(hydroxy)phenyllactates as acceptors resulting in ester formation while shikimate and quinate were not accepted. Unexpectedly, amino acids (D-phenylalanine, D-tyrosine, D-DOPA) also yielded products, showing that RAS can putatively catalyze amide formation. CbHST was able to transfer cinnamic, 4-coumaric, caffeic, ferulic as well as sinapic acid from CoA to shikimate but not to quinate or acceptor substrates utilized by CbRAS. In addition, 3-hydroxyanthranilate, 3-hydroxybenzoate and 2,3-dihydroxybenzoate were used as acceptor substrates. The reaction product with 3-aminobenzoate putatively is an amide. For both enzymes, structural requirements for donor and acceptor substrates were deduced. The acceptance of unusual acceptor substrates by CbRAS and CbHST resulted in the formation of novel compounds. The rather relaxed substrate as well as reaction specificity of both hydroxycinnamoyltransferases opens up possibilities for the evolution of novel enzymes forming novel secondary metabolites in plants and for the in vitro formation of new compounds with putatively interesting biological activities.
authors.affiliation: Institut für Pharmazeutische Biologie und Biotechnologie, Philipps-Universität Marburg, Deutschhausstr. 17A, 35037 Marburg, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Sander
authors.forename: Maike
authors.initials: M
authors.lastname: Petersen
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D002934:Cinnamates / Q000378:metabolism; D031330:Coleus / Q000201:enzymology* / Q000235:genetics; D003373:Coumaric Acids / Q000378:metabolism; D053630:Depsides / Q000378:metabolism; D004789:Enzyme Activation; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D010666:Phenylpropionates / Q000378:metabolism*; D011801:Quinic Acid / Q000378:metabolism; D012765:Shikimic Acid / Q000378:metabolism; D013379:Substrate Specificity; D000097123:Rosmarinic Acid
chemical_list: D000217:Acyltransferases; D002934:Cinnamates; D003373:Coumaric Acids; D053630:Depsides; D010666:Phenylpropionates; D011801:Quinic Acid; D012765:Shikimic Acid; D000097123:Rosmarinic Acid; C035253:3-phenylpropionic acid; C073734:sinapinic acid