The core of our research efforts is the isolation and characterization of novel desaturase and acetylenase genes from plants and club fungi (Basidiomycetes). Structure/function studies of this class of enzymes and the development of chemical probes will provide insight into a critical area of biochemistry, unsaturated fatty acid metabolism, as well as uncover pathways to an expansive array of bioactive acetylenic natural products. Many of these compounds have therapeutic and economic potential as antimicrobial and antiproliferative agents and HIV reverse-transcriptase inhibitors.
Controlled manipulation of unsaturated and acetylenic fatty acid metabolism in valuable oilseed and vegetable crops may be lead to altered oil compositions (e.g., enhanced nutritional benefit), unusual fatty acid components (e.g., eco-friendly lubricants), or increased fungal resistance. Despite the valuable bioactivities of these compounds, many details of the unusual enzymatic reactions required for the formation of acetylenic natural products remain elusive. A central objective of our research program is the isolation and investigation of novel desaturase and acetylenase genes from plants and gilled fungi (Basidiomycetes), and the development of synthetic chemistry to aid in characterization of the corresponding enzymes.
A specific, current goal is to isolate genes for the acetylenase enzymes in the Basidiomycetes. High similarity between the known acetylenases and the desaturases, enzymes responsible for eukaryotic unsaturated fatty acid biosynthesis, should allow a structure/function analysis of their mechanistic differences. Of particular interest is the isolation of acetylenase genes from Fistulina hepatica and the chanterelle, both edible mushrooms found in Indiana. Acetylenase and desaturase genes cloned from chanterelles are active when expressed in yeast. Acetylenic metabolites from F. hepatica cultures are being isolated by high-performance liquid chromatography and characterized prior to genetic studies. In conjunction with these projects, syntheses of highly unsaturated enzyme substrates and inhibitors are being developed for use in mechanistic studies of alkyne formation. A related area of interest examines the roles of unsaturated lipids in membrane structure and the interactions between plant acetylenase/desaturase enzymes and lipid bilayers. These structures, studied in collaboration with Prof. Gary Lorigan (Miami University, Oxford, OH), are probed by circular dichroism, solution NMR, and solid-state NMR spectroscopic methods. An examination of the order and motion in isotopically labeled lipids in the presence of transmembrane peptides or membrane components provides insight into the organization of the bilayer.