Vanillin formation from ferulic acid in Vanilla planifolia is catalysed by a single enzyme

• Published in: Nature communications 2014-06, Vol.5 (1), p.4037-4037, Article 4037
• Main Authors: Gallage, Nethaji J., Hansen, Esben H., Kannangara, Rubini, Olsen, Carl Erik, Motawia, Mohammed Saddik, Jørgensen, Kirsten, Holme, Inger, Hebelstrup, Kim, Grisoni, Michel, Møller, Birger Lindberg
• Format: Article
• Language: English
• Subjects: 14/32; 14/63; 38; 38/22; 38/23; 38/39; 38/70; 38/77; 38/79; 631/61/447; 82/29; 82/58; 82/80; Benzaldehydes - chemistry; Benzaldehydes - metabolism; Biocatalysis; Biosynthetic Pathways; Coumaric Acids - chemistry; Coumaric Acids - metabolism; Humanities and Social Sciences; multidisciplinary; Plant Proteins - chemistry; Plant Proteins - genetics; Plant Proteins - metabolism; Science; Science (multidisciplinary); Vanilla - chemistry; Vanilla - enzymology; Vanilla - genetics
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms5037

Vanillin is a popular and valuable flavour compound. It is the key constituent of the natural vanilla flavour obtained from cured vanilla pods. Here we show that a single hydratase/lyase type enzyme designated vanillin synthase ( Vp VAN) catalyses direct conversion of ferulic acid and its glucoside into vanillin and its glucoside, respectively. The enzyme shows high sequence similarity to cysteine proteinases and is specific to the substitution pattern at the aromatic ring and does not metabolize caffeic acid and p -coumaric acid as demonstrated by coupled transcription/translation assays. Vp VAN localizes to the inner part of the vanilla pod and high transcript levels are found in single cells located a few cell layers from the inner epidermis. Transient expression of VpVAN in tobacco and stable expression in barley in combination with the action of endogenous alcohol dehydrogenases and UDP-glucosyltransferases result in vanillyl alcohol glucoside formation from endogenous ferulic acid. A gene encoding an enzyme showing 71% sequence identity to Vp VAN was identified in another vanillin-producing plant species Glechoma hederacea and was also shown to be a vanillin synthase as demonstrated by transient expression in tobacco. Vanilla is derived from vanillin isolated from a vanillin-producing orchid, but the process is laborious, costly and results in a small yield. Here, the authors identified an enzyme from the orchid, Vanilla planifolia , that is able to catalyse the formation of vanillin and vanillin glucoside from ferulic acid and its glucoside in vitro , respectively.