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First published online June 28, 2007; 10.1104/pp.107.098970 Plant Physiology 144:1986-1999 (2007) © 2007 American Society of Plant Biologists OPEN ACCESS ARTICLE
Related Arabidopsis Serine Carboxypeptidase-Like Sinapoylglucose Acyltransferases Display Distinct But Overlapping Substrate Specificities1,[OA]Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907 (C.M.F., M.G.T., A.M.S., J.A.S., T.S., M.C.H., C.C.); and United States Dairy Forage Research Center, United States Department of Agriculture-Agricultural Research Service, Madison, Wisconsin 53706 (J.R.)
The Arabidopsis (Arabidopsis thaliana) genome encodes 51 proteins annotated as serine carboxypeptidase-like (SCPL) enzymes. Nineteen of these SCPL proteins are highly similar to one another, and represent a clade that appears to be unique to plants. Two of the most divergent proteins within this group have been characterized to date, sinapoyl-glucose (Glc):malate sinapoyltransferase and sinapoyl-Glc:choline sinapoyltransferase. The fact that two of the least related proteins within this clade are acyltransferases rather than true serine carboxypeptidases suggests that some or all of the remaining members of this group may have similar activities. The gene that encodes sinapoyl-Glc:malate sinapoyltransferase (sinapoyl-Glc accumulator1 [SNG1]: At2g22990) is one of five SCPL genes arranged in a cluster on chromosome 2. In this study, an analysis of deletion mutant lines lacking one or more genes in this SCPL gene cluster reveals that three of these genes also encode sinapoyl-Glc-dependent acyltransferases. At2g23000 encodes sinapoyl-Glc:anthocyanin acyltransferase, an enzyme that is required for the synthesis of the sinapoylated anthocyanins in Arabidopsis. At2g23010 encodes an enzyme capable of synthesizing 1,2-disinapoyl-Glc from two molecules of sinapoyl-Glc, an activity shared by SNG1 and At2g22980. Sequence analysis of these SCPL proteins reveals pairwise percent identities that range from 71% to 78%, suggesting that their differing specificities for acyl acceptor substrates are due to changes in a relatively small subset of amino acids. The study of these SCPL proteins provides an opportunity to examine enzyme structure-function relationships and may shed light on the role of evolution of hydroxycinnamate ester metabolism and the SCPL gene family in Arabidopsis and other flowering plants.
1 This work was supported by the National Science Foundation (grant no. 0091419 to C.C.) and a graduate fellowship from Purdue University (to C.M.F.). J.R. was supported in part by funding through the Department of Energy Biosciences program (grant no. DE–AI02–00ER15067). NMR experiments on the Bruker DMX-500 cryoprobe system were carried out at the National Magnetic Resonance Facility at Madison with support from the National Institutes of Health Biomedical Technology Program (grant no. RR02301) and additional equipment funding from the University of Wisconsin National Science Foundation Academic Infrastructure Program (grant no. BIR–9214394), National Institutes of Health Shared Instrumentation Program (grant nos. RR02781 and RR08438), National Science Foundation Biological Instrumentation Program (grant no. DMB–8415048), and the U.S. Department of Agriculture. A portion of the mass spectrometry analysis was conducted at the Purdue University Metabolic Profiling Facility, supported by the National Science Foundation (grant no. DBI–0421102). This is journal number 2007–18146 from the Purdue University Agricultural Experiment Station. 2 Present address: Department of Chemistry, Purdue University, West Lafayette, IN 47907. 3 Present address: BASF Plant Science L.L.C., 26 Davis Drive, Research Triangle Park, NC 27709. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Clint Chapple (chapple{at}purdue.edu). [OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.107.098970 * Corresponding author; e-mail chapple{at}purdue.edu; fax 765–494–7897. Received March 6, 2007; accepted June 22, 2007; published June 28, 2007. This article has been cited by other articles:
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