Cloning and characterization of NADPH-dependent double-bond reductases from Alnus sieboldiana that recognize linear diarylheptanoids as substrates

Diarylheptanoids are secondary metabolites of plants that comprise a C6–C7–C6 scaffold. They can be broadly classified into linear-type and cyclic-type diarylheptanoids based on their chemical structures. Actinorhizal trees, such as Casuarina, Alnus, and Myrica, which form nodule symbiosis with acti...

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Published in:Phytochemistry (Oxford) 2023-11, Vol.215, p.113850-113850, Article 113850
Main Authors: Takemoto, Konosuke, Tsurugi-Sakurada, Akiho, Moriuchi, Ryota, Yoneda, Yuko, Kawai, Shingo
Format: Article
Language:English
Subjects:
Actinorhizal symbiosis
Alnus sieboldiana
Alnusonol
Betulaceae
Bisdemethoxycurcumin
Curcumin
Cyclic diarylheptanoids
Diarylheptanoids
Double-bond reductase
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Summary:Diarylheptanoids are secondary metabolites of plants that comprise a C6–C7–C6 scaffold. They can be broadly classified into linear-type and cyclic-type diarylheptanoids based on their chemical structures. Actinorhizal trees, such as Casuarina, Alnus, and Myrica, which form nodule symbiosis with actinomycetes Frankia, produce cyclic diarylheptanoids (CDHs); in Alnus sieboldiana Matsum. in particular, we have reported that the addition of CDHs leads to an increase in the number of nodules. However, the information available on the biosynthesis of CDHs is scarce. A greater number of plants CDHs (including those isolated from actinorhizal trees) with a saturated heptane chain have been isolated compared with linear, non-cyclic diarylheptanoids. To identify the genes involved in the synthesis of these compounds, genes with significant sequence similarity to existing plant double-bond reductases were screened in A. sieboldiana. This report describes the isolation and characterization of two A. sieboldiana double-bond reductases (AsDBR1 and AsDBR2) that catalyze the NADPH-dependent reduction of bisdemethoxycurcumin and curcumin. The optimum pH for the two enzymes was 5.0. The apparent Km values for bisdemethoxycurcumin and NADPH were 4.24 and 3.53 μM in the case of AsDBR1, and 2.55 and 2.13 μM for AsDBR2. The kcat value was 9.4-fold higher for AsDBR1 vs. AsDBR2 when using the bisdemethoxycurcumin substrate. Interestingly, the two AsDBRs failed to reduce the phenylpropanoid monomer. [Display omitted] •Two double-bond reductases (AsDBR1 and AsDBR2) were isolated from Alnus sieboldiana.•Two reductases recognized α,β-unsaturated diarylheptanoids as specific substrates.•There was a 9.4-fold difference in turnover number (kcat) between the two reductases.•AsDBRs are the first diarylheptanoid C–C double-bond reductases reported in plants.
ISSN:0031-9422
1873-3700
DOI:10.1016/j.phytochem.2023.113850