Abstract
Coumarin is the main component of sweet aroma of cherry flower (Cerasus lannesiana) and is utilized for the Japanese sweets. Coumarin is biosynthesized via ortho(2'-)hydroxylation of trans-cinnamic acid, while an ortho-hydroxylase (ClC2'H) has not yet been identified from C. lannesiana. We have already identified feruloyl-CoA ortho(6')-hydroxylase from Arabidopsis thaliana, which is a key in scopoletin biosynthesis. Because both ClC2'H and AtF6'H1 catalyze ortho-hydroxylation of cinnamate, it is possible that ClC2'H is a homolog of AtF6'H1. The leaves of C. lannesiana leaves contain the very low level of coumarin but accumulate the β-glucoside of 2'-hydroxycinnamic acid as the precursor of coumarin. After wounding, the glucoside is hydrolyzed by a β-glucosidase, and the released 2'-hydroxycinnamic acid is spontaneously lactonized to coumarin. In this study, we have performed screening of ClC2'H and β-glucosidase from C. lannesiana.
