1 Section for Plant Biochemistry, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet2 Evolva A/S3 Section for Plant and Soil Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet4 Institut for Molekylærbiologi og Genetik - Afgrødegenetik og Bioteknologi5 Centre de Coopération Internationale en Recherche Agronomique pour le Dévelopement6 Section for Plant Biochemistry, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet7 Section for Plant and Soil Sciences, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet
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 (VpVAN) 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. VpVAN 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 VpVAN 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.
Nature Communications, 2014, Vol 5, Issue 6, p. 1-14