Journal of Oil Palm Research Vol. Special Issue  1999 Oct p.  34-45

Regulation of triacylglycerol synthesis in oil palm (Elaeis guineensis) and olive (Olea europaea) callus cultures

Author(s): UMI SALAMAH, R*; QUANT, P A**; HARWOOD, J L**

We have been using callus cultures as convenient model systems to understand any step where regulation of flux control in the triacylglycerol biosynthesis pathway may be important in two major oil-rich fruits, oil palm (Elaeis guineensis) and olive (Olea europaea). Top-down metabolic control analysis (TDCA) has been used to address the question of where possible control step(s) in the lipid biosynthesis pathway are located. With this method, lipid metabolism is conceptually divided into blocks of reactions and these are manipulated to see the effect on a key intermediate. We initially measured changes in the overall flux of carbon from [1-14C]acetate as modified by temperature in oil palm and olive callus cultures. A doubling of lipid synthesis with a 10ºC rise from 20ºC to 30ºC did not, however, cause much change in radioactivity incorporation into the acylthioester pools, acyl-CoAs and acyl-ACPs. This suggested that de novo fatty acid synthesis reactions exerted higher control than complex lipids assembly via Kennedy pathway.

Reactions of the Kennedy pathway were examined in more detail in oil palm callus cultures. By using microsomal fractions pre-pared from such cultures, we showed that radioactivity from [U-14C]glycerol 3-phosphate was effectively incorporated into intermediates of the Kennedy pathway and that the changes in radioactivity caused by temperature manipulation reflected well the endogenous lipid pool levels. Stimulation of triacylglycerol synthesis at 30ºC was accompanied by slight increases in diacylglycerol and phosphatidic acid. This indicates that at higher rates of triacylglycerol synthesis, specific enzymes of the Kennedy pathway may become more limiting.

Keywords: , , ,

Author Information
* Cardiff School of Biosciences, Cardiff University, Cardiff CF1 3US, U.K.

** Insitute of Child Health, University College London, London WC1N 1EH, U.K.

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