Diacylglycerol acyltransferase in maturing sunflower seeds

Developing sunflower seeds exhibit a high diacylglycerol acyltransferase (DAGAT, EC 2.3.1.20) activity. The distribution of the enzyme has been studied in subcellular fractions prepared by differential centrifugation of seed homogenate. Its activity was characterized using [1-C-14]oleoyl-CoA and diolein dispersed in Tween 20. Some properties of the microsomal fraction of DAGAT were investigated. Hyperbolic kinetics were observed, the apparent K-m was 60 muM and the specific activity of the reaction 15 pmol/min/mg of protein. Addition of BSA (0.1 %) stimulated oleate incorporation, which was not dependent on the presence of exogenous diacylglycerol. Detergents which might solubilize DAGAT, Triton X-100 and CHAPS, were tested for enzyme inhibition, and CHAPS was found to be the least denaturing.