OPEN ACCESS ARTICLE

This Article Free via Open Access: OA OA Full Text Full Text (PDF) Supplemental Data OA All Versions of this Article: 149/1/384    most recent pp.108.128066v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Koeduka, T. Articles by Pichersky, E. Search for Related Content PubMed PubMed Citation Articles by Koeduka, T. Articles by Pichersky, E. Agricola Articles by Koeduka, T. Articles by Pichersky, E.

BIOCHEMICAL PROCESSES AND MACROMOLECULAR STRUCTURES

Biosynthesis of t-Anethole in Anise: Characterization of t-Anol/Isoeugenol Synthase and an O-Methyltransferase Specific for a C7-C8 Propenyl Side Chain^1,[W],[OA]

Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109–1048 (T.K., E.P.); and Howard Hughes Medical Institute, Jack H. Skirball Chemical Biology and Proteomics Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037 (T.J.B., J.P.N.)

The phenylpropene t-anethole imparts the characteristic sweet aroma of anise (Pimpinella anisum, family Apiaceae) seeds and leaves. Here we report that the aerial parts of the anise plant accumulate t-anethole as the plant matures, with the highest levels of t-anethole found in fruits. Although the anise plant is covered with trichomes, t-anethole accumulates inside the leaves and not in the trichomes or the epidermal cell layer. We have obtained anise cDNA encoding t-anol/isoeugenol synthase 1 (AIS1), an NADPH-dependent enzyme that can biosynthesize t-anol and isoeugenol (the latter not found in anise) from coumaryl acetate and coniferyl acetate, respectively. In addition, we have obtained a cDNA encoding S-[methyl-¹⁴C]adenosyl-L-methionine:t-anol/isoeugenol O-methyltransferase 1 (AIMT1), an enzyme that can convert t-anol or isoeugenol to t-anethole or methylisoeugenol, respectively, via methylation of the para-OH group. The genes encoding AIS1 and AIMT1 were expressed throughout the plant and their transcript levels were highest in developing fruits. The AIS1 protein is 59% identical to petunia (Petunia hybrida) isoeugenol synthase 1 and displays apparent K_m values of 145 µM for coumaryl acetate and 230 µM for coniferyl acetate. AIMT1 prefers isoeugenol to t-anol by a factor of 2, with K_m values of 19.3 µM for isoeugenol and 54.5 µM for S-[methyl-¹⁴C]adenosyl-L-methionine. The AIMT1 protein sequence is approximately 40% identical to basil (Ocimum basilicum) and Clarkia breweri phenylpropene O-methyltransferases, but unlike these enzymes, which do not show large discrimination between substrates with isomeric propenyl side chains, AIMT1 shows a 10-fold preference for t-anol over chavicol and for isoeugenol over eugenol.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Eran Pichersky (lelx{at}umich.edu).

^[W] The online version of this article contains Web-only data.

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.128066

^* Corresponding author; e-mail lelx{at}umich.edu.

Received August 13, 2008; accepted October 30, 2008; published November 5, 2008.