Cinnamyl alcohol dehydrogenase (CAD) catalyzes cinnamyl aldehydes into cinnamyl alcohols, the final step in lignin biosynthesis. In this studied the purification, identification and characterization of a new cinnamyl alcohol dehydrogenase gene isolated from Citrus platymamma hort. Ex Tanaka. We expressed CAD potential gene in E.coli and then characterized its features in variety of specificity aldehydes substrates. The recombinant CAD protein was shown highest efficiently catalytic toward cinnamyl and coniferyl aldehydes and the shown lowest efficiently catalytic toward sinapyl aldehydes. We used a new improved analytical HPLC method in CAD enzymatic assay for fast and accurately measurement in various aldehydes substrates. In conclusion, our studies indicated the enzymatic activity of cDNA cloned CAD protein from Citrus platymamma hort. Ex Tanaka.

Cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.95), catalyzes the reduction of hydroxycinnamaldehydes to give hydroxycinnamyl alcohols, or "monolignols," the monomeric precursors of lignin. Lignins are important components of cell walls and lignified secondary cell walls play crucial roles in long distance transport of water and nutrients during plant growth and development and in plant defense against biotic and abiotic stresses. Here a cDNA clone containing a CAD gene, named as PgCAD, was isolated from a commercial medicinal plant Panax ginseng. PgCAD is predicted to encode a precursor protein of 177 amino acid residues, and its sequence shares high homology with a number of other plant CADS. The expression of PgCAD in adventitious roots and hairy roots of P. ginseng was analyzed using reverse transcriptase (RT)-PCR under various abiotic stresses such as salt, salicylic acid, wounding and chilling treatment that triggered a significant induction of PgCAD at different time points within 2-48 h post-treatment. This study revealed that PgCAD may help the plants to survive against various abiotic stresses.