Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/29/2003
Publication Date: 3/10/2004
Citation: Lin, J.T., Ikeda, M.D., Mckeon, T.A. 2004. Comparison of the incorporation of oleate and ricinoleate into phosphatidylcholines and acylglycerols in soybean microsomes. Journal of Agricultural and Food Chemistry. 2004. 52: 1152-1156 Interpretive Summary: Ricinoleate (a hydroxy fatty acid) has many industrial uses such as the manufacture of aviation lubricant, plastics, paints, coatings and cosmetics. Its only commercial source is castor bean. Since castor bean contains the toxin ricin as well as potent allergens, it is hazardous to grow, harvest and process. It would be desirable to produce ricinoleate instead in a transgenic oilseed lacking these toxic components. We have recently reported the biosynthetic pathway of castor oil and identified the key enzymatic steps, which drive ricinoleate into castor oil in castor bean. We have also identified and quantified molecular species of various lipid classes incorporated from various radiolabeled fatty acids. Soybean may be the transgenic oilseed to produce ricinoleate in the future. We would like to compare the incorporation of oleate (endogenous fatty acid) and ricinoleate (non-endogenous fatty acid) into various lipid classes and to find out the blocking step if any in the incorporation of ricinoleate into oil in soy bean. Ricinoleate can be incorporated well into soybean oil in soybean.
Technical Abstract: The incorporation of oleate (endogenous) and ricinoleate (non-endogenous) into phosphatidylcholine (PC) and acylglycerol (AG) in immature soybean microsomes were compared. [14C]Oleate and [14C]ricinoleate were incubated individually with soybean microsomal preparations for up to four hours and molecular species of PC and AG incorporated were identified and quantified by HPLC. The activities of acyl CoA:lysoPC acyltransferase and phospholipase A2 are in general not affected by the fatty acid (FA) chain at the sn-1 position. However comparing between oleate and ricinoleate, different FA incorporated at sn-2 of PC showed some different selection of the molecular species of lysoPC. The incorporation of [14C]ricinoleate into triacylglycerols (TAG) was slightly better than that of [14C]oleate and indicated that soybean was capable of incorporating ricinoleate into TAG when ricinoleate can be produced endogenously in a transgenic soybean. The incorporation of FA into TAG in soybean microsomes was much slower than those in castor microsomes.