Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 9/12/2003
Publication Date: 11/5/2003
Citation: Mckeon, T.A., Turner, C., He, X., Chen, G.Q., Lin, J.T. 2003. Application of lipases to develop novel acyltransferase substrates. Meeting Abstract. Interpretive Summary: Castor oil is an important industrial feedstock which is used to produce engineering plastics, greases, and numerous other products, but is currently 100% imported. We have isolated the gene for the acyltransferase enzyme that carries out the last step in oil biosynthesis, and describe in this Proceedings paper the method for making substrates for this enzyme. These substrates contain hydroxy-fatty acids and are difficult to make chemically. This paper presents a method that uses enzyme (lipase) reactions and demonstrates that the substrate works with a general plant acyltransferase. We will use this research to identify the key enzyme parameters in castor oil biosynthesis, with a final goal of developing alternate domestic sources of castor oil.
Technical Abstract: 1,2-Diacylglycerols (DAG) are the native substrates for the diacylglycerol acyltransferase. While DAG containing saturated or unsaturated fatty acids are relatively easy to make chemically, it is difficult to chemically synthesize DAG containing hydroxy fatty acids in specific positions on the glycerol backbone. An alternate approach is to start from acylglycerols containing hydroxy fatty acids, and selectively remove fatty acid chains to obtain the desired acylglycerol. The purpose of this study was to identify optimal parameters for lipase-catalyzed methanolysis of triricinolein to produce 1,2(2,3)-diricinolein, the substrate for biosynthesis of triricinolein in castor (Ricinus communis). We tested four different immobilized lipases, using n-hexane and diisopropyl ether (DIPE) as reaction media, and three different water activities. We followed the consumption of triricinolein and the formation of diricinolein, methyl ricinoleate and ricinoleic acid during the course of the reaction. Penicillium roquefortii lipase gave the highest yield of 1,2(2,3)-diricinolein and this lipase showed the highest specificity for the studied reaction, i.e. high selectivity for reaction with triricinolein, but low for diricinolein. The diacylglycerol produced can be acylated by the diacylglycerol acyltransferase from Arabidopsis thaliana. Therefore, the product of the lipase reaction is a suitable substrate for acyltransferase reactions.