Stilbenecarboxylate biosynthesis: a new function in the family of chalcone synthase-related proteins
| Autor: | Jürgen Schmidt, Christian Eckermann, Gudrun Schröder, Stefan Eckermann, Dieter Strack, Joachim Schröder, Bernd Schneider |
|---|---|
| Rok vydání: | 2003 |
| Předmět: |
Chalcone synthase
Stereochemistry Molecular Sequence Data Hydrangeic acid Plant Science Horticulture Biology Hydrangea Biochemistry Decarboxylation Substrate Specificity chemistry.chemical_compound Polyketide Chalcone Biosynthesis Coumarins Stilbenes Benzopyrans Coenzyme A Amino Acid Sequence Cloning Molecular Molecular Biology Peptide sequence chemistry.chemical_classification Sequence Homology Amino Acid Lunularic acid General Medicine Recombinant Proteins Salicylates Amino acid Enzyme chemistry Amino Acid Substitution Isocoumarins biology.protein Electrophoresis Polyacrylamide Gel Acyltransferases |
| Zdroj: | Phytochemistry. 62(3) |
| ISSN: | 0031-9422 |
| Popis: | Chalcone (CHS), stilbene (STS) synthases, and related proteins are key enzymes in the biosynthesis of many secondary plant products. Precursor feeding studies and mechanistic rationalization suggest that stilbenecarboxylates might also be synthesized by plant type III polyketide synthases; however, the enzyme activity leading to retention of the carboxyl moiety in a stilbene backbone has not yet been demonstrated. Hydrangea macrophylla L. (Garden Hortensia) contains stilbenecarboxylates (hydrangeic acid and lunularic acid) that are derived from 4-coumaroyl and dihydro-4-coumaroyl starter residues, respectively. We used homology-based techniques to clone CHS-related sequences, and the enzyme functions were investigated with recombinant proteins. Sequences for two proteins were obtained. One was identified as CHS. The other shared 65-70% identity with CHSs and other family members. The purified recombinant protein had stilbenecarboxylate synthase (STCS) activity with dihydro-4-coumaroyl-CoA, but not with 4-coumaroyl-CoA or other substrates. We propose that the enzyme is involved in the biosynthesis of lunularic acid. It is the first example of a STS-type reaction that does not lose the terminal carboxyl group during the ring folding to the end product. Comparisons with CHS, STS, and a pyrone synthase showed that it is the only enzyme exerting a tight control over decarboxylation reactions. The protein contains unusual residues in positions highly conserved in other CHS-related proteins, and mutagenesis studies suggest that they are important for the structure or/and the catalytic activity. The formation of the natural products in vivo requires a reducing step, and we discuss the possibility that the absence of a reductase in the in vitro reactions may be responsible for the failure to obtain stilbenecarboxylates from substrates like 4-coumaroyl-CoA. |
| Databáze: | OpenAIRE |
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