Poster: Secondary Metabolism

Abs # 305: Cloning and Characterization of Redox Enzymes in Peppermint Monoterpene Biosynthesis

Presenter:	Ringer, Kerry , kringer@wsu.edu
Authors	Ringer, Kerry  (A)   Davis, Edward  (A)   McConkey, Marie  (A)
Affiliations:	(A): Washington State University

Monoterpenes (C₁₀) comprise one of the major components of the essential oils of the mint (Lamiaceae) family. In peppermint, monoterpene biosynthesis is localized in the secretory cells of the leaf glandular trichomes. Limonene, the cyclic precursor of the peppermint monoterpenes, undergoes several secondary transformations to form primarily menthol. These transformations are catalyzed mainly by redox enzymes including an NAD-dependent dehydrogenase, an endocyclic and an exocyclic double bond reductase, as well as two stereoselective carbonyl reductases. Recently, a cDNA library was constructed from mRNA isolated from the secretory cells of peppermint leaf glandular trichomes, resulting in a library highly enriched in cDNAs encoding monoterpene biosynthetic enzymes. Random sequencing of cDNA clones and bioinformatics selection allowed for the identification of putative redox enzymes. These were screened by functional expression in E. coli. This strategy yielded cDNA clones for several of the redox enzymes. These recombinant redox enzymes have been expressed, purified and biochemically characterized including enzyme kinetics, substrate specificity, product profile, and sequencing.