Minisymposium 5: Secondary Metabolism

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Abs # M0502: The biosynthesis of volatile phenylpropenes involves unexpected phenylpropanoid ester reduction

Presenter:	Gang, David R       Contact Presenter
Authors	Gang, David R (A)   Koeduka, Takao  (B)   Fridman, Eyal  (B)   Qualley, Anthony  (C)   Vassao, Daniel G (D)   Jackson, Brenda L (A)   Kish, Christine M (C)   Orlova, Irina  (C)   Spassova, Snejina M (E)   Dexter, Richard  (F)   Lewis, Norman G (D)   Clark, David  (F)   Noel, Joseph P (E)   Baig, Tom  (E)   Dudareva, Natalia  (C)   Pichersky, Eran  (B)
Affiliations:	(A): University of Arizona (B): University of Michigan (C): Purdue University (D): Washington State University (E): The Salk Institute for Biological Studies (F): University of Florida
Web Site:	http://ag.arizona.edu/research/ganglab/index.htm

Eugenol and related volatile phenylpropenes, such as isoeugenol, and methylchavicol, are important components of many economically important spices and are highly valued as flavoring/fragrance additives and for their biological properties. For example, these spices have been used for centuries as food preservation agents. These compounds are widely distributed in the plant kingdom, and are produced by plants as defense compounds against animals and microorganisms and as floral attractants of pollinators. Previous research suggested that the phenylpropenes are synthesized in plants via the phenylpropanoid pathway, although the identity of the enzymes and the nature of the reaction mechanisms involved in their formation remained obscure. We have identified in glandular trichomes of sweet basil (Ocimum basilicum L.), which are known to synthesize and accumulate large amounts of such phenylpropenes, an enzyme, which we have called eugenol synthase (EGS), that uses esters of coniferyl alcohol to form eugenol and of p-coumaryl alcohol to form chavicol. Petunia (Petunia hybrida L. Mitchell) flowers, which emit large amounts of isoeugenol, possess a homologous protein (isoeugenol synthase, IGS) that also uses coniferyl alcohol esters as substrate, but instead of forming eugenol, IGS forms isoeugenol. We have obtained the corresponding cDNAs and characterized the recombinant proteins. In addition, we have identified in these plants the acyltransferases responsible for formation of the substrates for EGS and IGS. The relationships of these enzymes (EGS, IGS and acyltransferases) to other members of their respective protein families, their substrate preferences, and a discussion of the catalytic mechanisms of EGS and IGS will be presented.