The C12 'earthy' odorant geosmin is derived from the C15 metabolite farnesyl diphosphate. Metabolic transformation now seems to be catalyzed by a bifunctional protein having two operatively independent sesquiterpene synthase domains. The domains are catalytically linked through the passive diffusion of a C15 alcohol product of the N-terminal catalytic domain to the C-terminal catalytic domain for the final steps of geosmin formation.
