Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2002
Publication Date: 8/28/2002
Citation: Lin, J.T., Chen, J.M., Liao, L., Mckeon, T.A. 2002. Molecular species of acylglycerols incorporating radiolabled fatty acids from castor (ricinus communis l.) microsomal incubations. Journal of Agricultural and Food Chemistry. 2002. 50: 5077-5081 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. In this report, we compare the incorporations of six radiolabeled fatty acids into castor oil in castor microsomal incubations. Sixty one incorporated molecular species of castor oil were identified and quantified.
Technical Abstract: We have identified and quantified sixty one molecular species of triacylglycerols (TAG) and diacylglycerols produced from castor microsomal incubations incorporating six different [14C]-labeled fatty acids. The preference for incorporation into TAG was in the order of: ricinoleate > oleate > linoleate > linolenate > stearate > palmitate. Ricinoleate was the major FA incorporated, while stearate, linolenate and palmitate were incorporated at low levels. Twenty one molecular species of AG (HPLC peaks) in castor oil have also been assigned. The levels of TAG in castor oil are: RRR (triricinolein) >> RR-TAG >> R-TAG > noR-TAG. The levels of the molecular species within the groups of RR-TAG, RL-TAG and LL-TAG individually are as: ricinoleate > linoleate > oleate > linolenate, stearate, and palmitate. The results of the labeled fatty-acid incorporation are consistent with ricinoleate being preferentially driven into TAG, and oleate being converted to ricinoleate in castor oil biosynthesis.