Study of the Asymmetric Distribution of Saturated Fatty Acids in Sunflower Oil Triacylglycerols

Abstract

Triacylglycerols (TAG) are the main components of vegetable oils, accounting for almost 100% of the weight. Each oil has a characteristic pattern of TAG and the chemical, physical and nutritional properties of a particular oil are determined mainly by the abundance of its different TAG molecular species. Plant triacylglycerols are produced by the classic Kennedy pathway which involves, initially, two acylations of glycerol 3-phosphate in sn-1 and sn-2 positions with acyl-CoA esters to produce phosphatidate by the enzymes, glycerol 3-phosphate acyltransferase (GPAT) and lysophosphatidate acyltransferase (LPAAT), respectively. The phosphatidate is then hydrolysed to diacylglycerol by the enzyme phosphatidate phosphohydrolase and, subsequently, the diacylglycerol can be further acylated by acyl-CoA to yield triacylglycerol (a reaction catalysed by diacylglycerol acyltransferase, DAGAT). The last enzyme being unique to triacylglycerol biosynthesis. Those acyltransferases regulate fatty acid stereochemical distribution. Therefore the acyltransferases specificity and the acyl-CoA pool control the proportion of the different TAG species formed. In order to study variability in the system of acyl-transferases in sunflower seeds a new extraction method has been developed. Using this method we were able to carry out triacylglycerols variability studies on sunflower seeds with high saturated fatty acid content (stearic >12%).