The biosynthesis and turnover of lipid during the differentiation of Dictyostelium discoideum.

Despite the fact that there are only relatively slight changes in lipid composition during the differentiation of Dictyostelium discoideum, the rates of lipid synthesis were found to vary considerably. Polar lipid synthesis declined markedly during aggregation and pseudoplasmodium formation and then increased during the terminal stages of differentiation. Several neutral lipid classes (sterol, the diacylglycerols and triacylglycerol) exhibited similar changes in synthetic rates, although the effects were somewhat less pronounced. In contrast, the rates of synthesis of steryl ester and free fatty acid increased slightly throughout the differentiation period, so that, by the end of the later stages of fruiting body culmination, the rates were essentially doubled. Finally, the synthesis of an unknown component increases at least 10-fold during differentiation. Of the newly synthesized lipid, only triacylglycerol and polar lipid exhibited marked turnover. Accumulation of radioactivity in steryl ester and free fatty acid continued after the removal of radioactive acetate, presumably due to the incorporation of fatty acid produced by polar lipid degradation.