title: Activities of Arabidopsis sinapoylglucose: malate sinapoyltransferase shed light on functional diversification of serine carboxypeptidase-like acyltransferases.
abstract: Analysis of the catalytic properties of the serine carboxypeptidase-like (SCPL) 1-O-sinapoyl-beta-glucose:l-malate sinapoyltransferase (SMT) from Arabidopsis showed that the enzyme exhibits besides its primary sinapoylation of l-malate, minor hydrolytic and disproportionation activities, producing free sinapic acid and 1,2-di-O-sinapoyl-beta-glucose, respectively. The ability of the enzyme to liberate sinapic acid from the donor molecule 1-O-sinapoyl-beta-glucose indicates the existence of a short-lived acylenzyme intermediate in the proposed random sequential bi-bi mechanism of catalysis. SMT-catalyzed formation of disinapoylglucose has been corroborated by docking studies with an established homology structure model that illustrates the possible binding of two 1-O-sinapoyl-beta-glucose molecules in the active site and the intermolecular reaction of the two glucose esters. The SMT gene is embedded in a tandem cluster of five SCPL sinapoyltransferase genes, which encode enzymes with high amino acid sequence identities and partially overlapping substrate specificities. We assume that in recent duplications of genes encoding SCPL proteins, neofunctionalization of the duplicates to accept 1-O-sinapoyl-beta-glucose as acyl donor was gained first, followed by subfunctionalization leading to different acyl acceptor specificities.
authors.affiliation: Department of Secondary Metabolism, Leibniz Institute of Plant Biochemistry (IPB), Weinberg 3, D-06120 Halle (Saale), Germany.
authors.forename: Felix
authors.initials: F
authors.lastname: Stehle
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Brandt
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schmidt
authors.forename: Carsten
authors.initials: C
authors.lastname: Milkowski
authors.forename: Dieter
authors.initials: D
authors.lastname: Strack
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D017360:Arabidopsis / Q000201:enzymology*; D002268:Carboxypeptidases / Q000378:metabolism*; D002384:Catalysis; D002934:Cinnamates / Q000378:metabolism; D017124:Conserved Sequence; D019143:Evolution, Molecular; D005960:Glucosides / Q000378:metabolism; D006868:Hydrolysis; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010777:Photochemistry; D016415:Sequence Alignment; D013379:Substrate Specificity
chemical_list: D002934:Cinnamates; D005960:Glucosides; C103373:sinapoylglucose; D000217:Acyltransferases; C416511:sinapoylglucose malate sinapoyltransferase; D002268:Carboxypeptidases; C022633:serine carboxypeptidase