|Pepperman Jr, Armand|
Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2004
Publication Date: 7/1/2004
Citation: Dyer, J.M., Chapital, D.C., Kuan, J.-C.W, Shepherd, H.S., Tang, F., and Pepperman, A.B. 2004. Production of linolenic acid in yeast cells expressing an omega-3 desaturase from tung (Aleurites fordii). Journal of the American Oil Chemists' Society. 81:647-651. Interpretive Summary: Problem Statement: While the majority of vegetable oils produced today are used in food and cooking applications, there is considerable interest in developing alternative uses for these oils to expand their marketability. For example, oils containg high amounts of polyunsaturated fatty acids can be used in formulation of inks, dyes, coatings and resins. Increasing the polyunsaturated fatty acid content of oils, however, requires identification of enzymes that are capable of producing high amounts of polyunsaturated fatty acids in oils. Accomplishment: We have identified an enzyme from the tung tree (Aleurites fordii) that, when expressed in yeast cells, produces up to 18% polyunsaturated fatty acids in the cells. This amount is 10-fold higher than the amount of polyunsaturated fatty acid produced by any other plant enzyme expressed in yeast cells. Contribution to society or science: The tung enzyme has great promise for increasing the polyunsaturated fatty acid content of vegetable oils. The enzyme also produces extraordinarily high amounts of polyunsaturated fatty acids in yeast cells. These yeast cells may serve as a platform for production of more specialized polyunsaturated fatty acids that could be used as food supplements.
Technical Abstract: Tung oil is an industrial drying oil containing approximately 90% polyunsaturated fatty acids. We previously reported on enzymes required for the synthesis of linoleic (6%) and eleostearic (80%) acids, and here describe the cloning and functional analysis of an omega-3 fatty acid desaturase (FAD3) required for the synthesis of linolenic acid (1%). The tung FAD3 cDNA was identified by screening a tung seed cDNA library using PCR and degenerate primers encoding conserved regions of the FAD3 enzyme family. Expression of this cDNA in yeast cells, cultured in the presence of linoleic acid, resulted in synthesis and accumulation of linolenic acid, which accounted for up to 18% wt/wt of total cellular fatty acids. Tung FAD3 activity was significantly affected by cultivation temperature, with the greatest amount of linolenic acid accumulating in yeast cells grown at 15 degree C. The amount of linolenic acid synthesized in yeast cells by tung FAD3 is approximately 10-fold higher than that observed by expression of a rapeseed (Brassica napus) FAD3 in yeast, suggesting that tung FAD3 might be useful for biotechnological production of omega-3 fatty acids in transgenic organisms.