Study of the biochemical formation pathway of aroma compound 1-phenylethanol in tea (Camellia sinensis (L.) O. Kuntze) flowers and other plants

摘要

After tea leaves, tea (Camellia sinensis) flowers are becoming a second tea plant resource because they contain not only functional metabolites similar to those found in tea leaves, but also predominant amounts of functional metabolites that only occur in tea leaves in small amounts. 1-Phenylethanol (1PE) is a predominant aroma compound found in tea flowers. A 1PE synthase in tea flowers was isolated, functionally characterized, and shown to have the highest catalytic efficiency for the conversion of acetophenone (AP). To determine why 1PE accumulates more in tea flowers than other plants, we compared their 1PE contents and used a stable isotope labeling method to elucidate the 1PE biosynthetic route. Supplementation with [H-2(8)]L-phenylalanine and [H-2(5)]AP suggested that most plants containing the enzyme/gene catalyzed the conversion of AP to 1PE. Furthermore, the availability of AP derived from L-phenylalanine was responsible for the difference in 1PE accumulation between tea flowers and other plants.