Frog farnesyl pyrophosphate synthases and their role as non-canonical terpene synthases for bisabolane sesquiterpenes

Three enzymes from African frogs with close sequence homology to avian farnesyl pyrophosphate synthase (FPPS) were studied for their function. All three enzymes converted (2Z,6E)-FPP into several bisabolane sesquiterpenes, with bisabolol and anymol as main products. Experiments with FPPS from Escherichia coli confirmed the same function, suggesting that the observed activity may be of general relevance for FPP synthases. Only one of the frog enzymes showed significant activity in the biosynthesis of FPP from terpene monomers, which may point to an evolutionary process that resulted in a functional switch from an FPPS to a bisabolane synthase. The physiological relevance of these findings is supported by the identification of bisabolol/anymol in gland extracts.