J. Reske et al., TRIACYLGLYCEROL COMPOSITION AND STRUCTURE IN GENETICALLY-MODIFIED SUNFLOWER AND SOYBEAN OILS, Journal of the American Oil Chemists' Society, 74(8), 1997, pp. 989-998
Changes in composition were examined in oils extracted from geneticall
y modified sunflower and soybean seeds. Improvements were made to the
analytical methods to accomplish these analyses successfully. Triacylg
lycerols (TAG) were separated on two 300 mm x 3.9 mm 4 mu Novapak C18
high-performance liquid chromatography (HPLC) columns and detected wit
h a Varex MKIII evaporative light-scattering detector. Peaks were iden
tified by coelution with known standards or by determining fatty acid
composition of eluted TAG by capillary gas chromatography (CC). Stereo
specific analysis (fatty acid position) was accomplished by partially
hydrolyzing TAG with ethyl magnesium bromide and immediately derivatiz
ing the resulting diacylglycerols (DAG) with (S)-(+)-1-(1-naphthyl)eth
yl isocyanate. The derivatized sn-1,2-DAG were completely resolved fro
m the sn-2,3-DAG on two 25 mm x 4.6 mm 3 mu silica HPLC columns. The c
olumns were chilled to -20 degrees C to obtain baseline resolution of
collected peaks. The distribution of fatty acids on each position of t
he glycerol backbone was derived from the fatty acid compositions of t
he two DAG groups and the unhydrolyzed oil. Results for the sn-2 posit
ion were verified by hydrolyzing oils with porcine pancreatic lipase,
isolating the resulting sn-2 monoacylglycerols by TLC, and determining
the fatty acid compositions by CC. Results demonstrated that alterati
ons in the total fatty acid composition of these seed oils are determi
ned by the concentration of TAC species that contain at least one of t
he modified acyl groups. As expected, no differences were found in TAG
with fatty acid quantities unaffected by the specific mutation. In li
eu of direct metabolic or enzymatic assay evidence, the authors' posit
ional data are nevertheless consistent with TAG biosynthesis in these
lines being driven by the mass action of available acyl groups and not
by altered specificity of the acyltransferases, the compounds respons
ible for incorporating fatty acids into TAG.