Functional characterization of rose phenylacetaldehyde reductase (PAR), an enzyme involved in the biosynthesis of the scent compound 2-phenylethanol

Abstract

2-Phenylethanol (2PE) is a prominent scent compound released from flowers of Damask roses (Rosa×damascena) and some hybrid roses (Rosa 'Hoh-Jun' and Rosa 'Yves Piaget'). 2PE is biosynthesized from l-phenylalanine (l-Phe) via the intermediate phenylacetaldehyde (PAld) by two key enzymes, aromatic amino acid decarboxylase (AADC) and phenylacetaldehyde reductase (PAR). Here we describe substrate specificity and cofactor preference in addition to molecular characterization of rose-PAR and recombinant PAR from R.×damascena. The deduced amino acid sequence of the full-length cDNA encoded a protein exhibiting 77% and 75% identity with Solanum lycopersicum PAR1 and 2, respectively. The transcripts of PAR were higher in petals than calyxes and leaves and peaking at the unfurling stage 4. Recombinant PAR and rose-PAR catalyzed reduction of PAld to 2PE using NADPH as the preferred cofactor. Reductase activity of rose-PAR and recombinant PAR were higher for aromatic and aliphatic aldehydes than for keto-carbonyl groups. Both PARs showed that (S)-[4-(2)H] NADPH was preferentially used over the (R)-[4-(2)H] isomer to give [1-(2)H]-2PE from PAld, indicating that PAR can be classified as short-chain dehydrogenase reductase (SDR).

Biosynthesis of floral scent 2-phenylethanol in rose flowers

“…Hypothetical biosynthetic pathways to [ 2 H n , n = 7, 8]-2PE from L-[ 2 H 8 ]Phe in rose flowers.Notes: "D" denotes the position of a deuterium atom. Dashed line indicates the hypothetical route38,39) and solid lines (route a, d) represent routes investigated in our studies 40,44,47,49). Rose AADC40) , petunia PAAS32) and Arabidopsis AAS41) catalyze L-[ 2 H 8 ]Phe decarboxylation, leading to [ 2 H 8 ] PAld (route a).…”

Comparative Transcriptome Reveals Benzenoid Biosynthesis Regulation as Inducer of Floral Scent in the Woody Plant Prunus mume

“…During the transformation of the phenylalanine, SDR family plays a vital role in the benzenoid volatiles. In the flowers of Damask roses, 2-Phenylethanol (2PE) is biosynthesized from phenylalanine via intermediate phenylacetaldehyde under the catalysis of PAR , which is classified as short-chain dehydrogenase reductase (Chen et al, 2011). The presence of highly expressed PmSDRs homologous to PAR satisfied the requirement of benzyl alcohol.…”

Transgenic Hybrid Poplar for Sustainable and Scalable Production of the Commodity/Specialty Chemical, 2-Phenylethanol

“…In this regard, an NCBI GenBank database BLAST search indicated presence of two P. trichocarpa cinnamoyl CoA reductase-like proteins having ∼76% amino acid identity (accession numbers XP_002314079.1 and XP_002298395.1, respectively) to LePAR1, and ∼84% identity to a rose PAR [31], perhaps suggesting that the entire pathway to PEA was in place in hybrid poplar. We thus transformed the hybrid poplar with PAR alone, but this gave no significant increase in PEA/PEA-Glc levels (data not shown).…”