|Pepperman Jr, Armand|
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/1998
Publication Date: N/A
Citation: Interpretive Summary: The seeds of many plants accumulate large amounts of oil that can be extracted for use in cooking or industrial processes. Two problems can be encountered by businesses that rely on plant oils: 1. Decreased demand for vegetable oils can result in surplus oils for farmers. 2. Foreign markets that supply industrial oils may become unreliable or cost prohibitive. The goal of our research is to address these two problems in a complementary, interdependent fashion. We are trying to identify plant enzymes that produce industrial oils so that we can use these enzymes to convert surplus vegetable oils to industrial oils. This will provide an alternative usage for excess vegetable oils while providing a new source of industrial oils. We have been studying the tung tree to find the enzymes that produce tung oil. Tung oil is used in many different manufacturing processes because of its unique drying qualities. Tung nuts were homogenized and fractionated into different subcellular compartments. A variety of techniques were used to isolate a small region of the cell that is likely to be involved in tung oil synthesis. This fraction was enriched in only three proteins. These proteins will be studied further to determine if they are the enzymes responsible for tung oil synthesis. The results presented in this manuscript represent basic science research and will not have an immediate impact on industry or the economy. However, this paper provides a substantial step forward in understanding how tung oil biosynthesis must be investigated. Therefore this research is of extreme importance to the scientific community.
Technical Abstract: Seeds of the tung tree (Aleurites fordii) contain large amounts of eleostearic acid, a conjugated trienoic fatty acid that imparts important drying qualities to tung oil. In an effort to characterize the biosynthesis of tung oil, tung seeds actively engaged in eleostearic acid synthesis were homogenized and fractionated into different subcellular components. A simple assay based on organic extraction of lipids and UV spectral properties of eleostearic acid was used to localize the production of eleostearic acid to a 104,000xg supernatant fraction. Production of eleostearic acid in this fraction required fatty acyl-CoA substrates, was sensitive to temperature, but did not require exogenous cofactors. HPLC/GC analysis of lipids isolated during the assay demonstrated that eleostearic acid was present as acyl-glycerolipids and had characteristics similar to mature tung oil. Further investigation of the lipids in the 104,000xg supernatant revealed that different pools of lipids were differentially extractable by organic solvents. Thus, the eleostearic acid detected during the course of the assay was due to conversion of an unextractable pool of eleostearic acid to an extractable one rather than de novo synthesis of the fatty acid. Proteinase K digestion and sucrose flotation experiments suggested that this unextractable pool was composed of lipid-protein particles. Isolation of the lipid-protein particles by centrifugation and analysis of proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed several proteins specifically associated with this lipid fraction.