Oil Bodies and Oil-Associated Proteins from Coconut (Cocos Nucifera L.): Characterization and a Modified Method for Isolation

Coconut oil bodies were isolated from 11-12 month old coconut samples using both liquid nitrogen-powdered solid endosperm and coconut milk extracted from the solid endosperm as starting material. The oil bodies were purified by sucrose density gradient washing, urea washing and floatation centrifugation. Purified oil bodies were observed under light microscope. Of 1055 oil bodies measured, up to 76% had a diameter in the range of 1-4 um. The average diameter of these oil bodies is 2.54 um. Up to 10 percent of the oil bodies had diameter several times larger (10 um) than the normal size (1-2 um). The oil bodies consisted of 97% triglycerols,the rest being phospholipids (Phosphophatidylethanolamine and phosphatidylcholine) and the oil body storage protein, oleosin. The purified oleosin showed one band of 14400 Mr on SDS-PAGE. Two dimensional electrophoresis also resolved one band of 14400 with an isoelectric pH between 9 and 10. N-terminal amino acid sequence analysis of the 14.4 kDa band gave GEERR or GEEER, and indicated the present of isoforms. Additional urea washings of the coconut oil bodies followed by ether delipidation revealed two oleosin bands of 14400 and 11000 Mr on SDS-PAGE.